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Choosing the right DC Motor (or DC gear motor) for a specific application can be a daunting task and many manufacturers only provide basic motor specifications. These basic specifications might not be sufficient for your needs. Listed below are ideal motor specifications and whenever possible, ways to approximate values.

BASIC SPECIFICATIONS

Below is a list of the most common specifications a DC motor manufacturer might list. For most hobbyists the basic information is enough to make an informed decision about which motor to purchase.

Nominal Voltage:

The voltage that corresponds to the highest motor efficiency. Try to choose a main battery pack which most closely matches the nominal voltage of your drive motors. For example, if the motor’s nominal voltage is 6V, use a 5x 1.2V NiMh pack to get 6V. If your motor operates at 3.5V nominal, you can use either a 3xAA or 3xAAA NiMh pack or a 3.7V LiPo or LiIon pack.

If you operate a motor outside of its nominal voltage, the efficiency of the motor goes down, often requiring additional current, generating more heat and decreasing the lifespan of the motor. Aside from a “nominal voltage” DC motors also have an operating voltage range outside of which the manufacturer does not suggest operating the motor. For example a 6V DC Gear motor may have an operating range of 3-9V; it will not operate as efficiently as compared to 6V, but it will still run well.

This is how fast (angular velocity) the final output shaft will rotate assuming nothing is connected to it. If the motor has a gear down and the motor’s speed is not indicated separately, the no load rpm value is the shaft speed after the gear down. The motor’s RPM is proportional to the voltage input. “No Load” means the motor encounters no resistance whatsoever (no hub or wheel mounted to the end). Usually the No Load RPM provided is associated with the nominal voltage.

Power rating:

If a motor’s power is not listed, it can be approximated. Power is related to current (I) and voltage (V) by the equation P = I*V. Use the no load current and nominal voltage to approximate the motor’s power output. The motor’s maximum power (which should only be used for a short time) can be approximated using the stall current and nominal voltage (rather than maximum voltage).

Stall Torque:

This is the maximum torque* a motor can provide with the shaft no longer rotating. It is important to note that most motors will sustain irreparable damage if subjected to stall conditions for more than a few seconds. When choosing a motor, you should consider subjecting it to no more than ~1/4 to 1/3 the stall torque.

Stall Current:

This is the current the motor will draw under maximum torque* conditions. This value can be very high and should you not have a motor controller capable of providing this current, there is a good chance your electronics will fry as well. If neither the stall nor the nominal current are provided, try to use the motor’s power rating (in Watts) and the nominal voltage to estimate the current: Power [Watts] = Voltage [Volts] x Current [Amps]

General Specifications:

A DC motor’s general specifications usually include weight, shaft length and shaft diameter as well as motor length and diameter. Other useful dimensions include the location of mounting holes and thread type. If only the length or diameter are provided, refer to an image, photo or scale drawing to get a sense of the other dimensions based on the one known value.

Torque

*”Torque” is calculated by multiplying a force (acting at a distance away from a pivot) by the distance. A motor rated at a stall torque of 10Nm can hold 10N at the end of 1m. Similarly, it could also hold 20N at the end of 0.5m (20 x 0.50 = 10) and so on.

Note: 1 Kg * force of gravity (9.81m/s2) = 9.81N (~10N for quick calculations)

IDEAL SPECIFICATIONS

Many motor manufacturers are now listing additional information that can be very useful when selecting the right motor. Below is some additional information you might come across when searching for DC motors:

Voltage vs. RPM:

Ideally, the manufacturer would list the graph of a motor’s voltage vs. rpm. For a quick approximate, consider using the no-load rpm and nominal voltage: (nominal voltage, rpm) and the point (0, 0). See “gear down” below for motors with a gear down.

Torque vs. Current:

Current is a value that cannot be easily controlled. DC motors use only as much current as they need. Ideal specifications include this curve, and approximations are not easily reproduced. The stall torque is related to the stall current. A motor that is prevented from turning will consume maximum (“stall”) current and produce the maximum torque possible. The current required to provide a given torque is based on many factors including the thickness, type and configuration of the wires used to make the motor, the magnets and other mechanical factors.

Technical specifications or 3D CAD drawing:

Many robot builders like to draw their robot on the computer before purchasing the necessary parts. Although all motor manufacturers have a CAD drawing with the dimensions, they rarely make it available to the public. Ideal motor dimensions include the basics listed above, as well as mounting hole locations and thread type. Ideally the materials used to make the motor, gears and winding as well as separate dimensions for the motor and the gear down would also be given.

Gear down:

DC motor manufacturers that also produce the corresponding gear down for a motor must list the gear down ratio. The gear down acts to increase torque and reduce rpm. The No Load RPM value given is always that of the last output shaft after the gear down. To find the angular velocity of the motor shaft before the gear down, multiply the value by the gear ratio. To obtain the motor’s stall torque before the gear down, divide the stall torque by the gear down. The material used to make the internal gears is usually plastic or metal and are chosen to be able to withstand the maximum torque rating. Calculate the gear down below given the values before and after gear down:

Accessories:

An optical encoder is the most common accessory for a gear motor. Finding the right size of optical encoder for your motor can be very difficult if it is not made from the same company. An optical encoder allows you to track both the direction of rotation and number of revolutions of the motor. With the right code, an optical encoder can also give you the angle of the shaft.

Hubs and Shaft Couplers:

Secondary items such as hubs (used to connect the output shaft to other items) are slowly becoming available for varying sized output shafts. Only a few manufacturers provide generic shaft couplers. If you cannot find the appropriate coupler, consider using spur gears to offset the shaft to that of a different size. The image below shows three different types of couplers. The hole in the hub is for a threaded screw (“set screw”) which presses tightly against the shaft.

318 Responses to “How Do I Interpret DC Motor Specifications?”

1. Zaeem Usman

What happens if we exceed the nominal voltage for example if we have a 3v dc motor and connect it to a 9v battery is there a chance that the motor will burn?

2. Carlos Asmat

If you exceed the tolerances of a components, you will release its magic blue smoke and your components will not work anymore (i.e. you will fry it) 🙂

3. Jeanine

I have a small DC hobbyist motor for which I cant find the current spec. It is 1.5v to 3v rated. How do I measure the watts to estimate the amps as you explained? And then can I just add a resistor to decrease the voltage in the circuit if I want to run it off a 9v battery?

• Coleman Benson

If you have a multimeter, you can actually measure the current consumed under different operating conditions. If you don’t, it’s a bit harder to do.
If you want to run a 3V motor off a 9V battery, it’s best to use a regulator (far more efficient than a resistor):
http://www.robotshop.com/en/power-regulators.html

4. shiva

Stall current : New terminology, will be better if we use a common universal terminology

• Coleman Benson

@shiva “stall current” is a term used my most manufacturers. What would you propose?

5. RAJ

if 30A is rated value of current give on data plate of DC motor. What does it specify line current or armature current

• Coleman Benson

@Raj The 30A value should ideally be associated with the current at maximum efficiency, maximum power or stall.

6. sathish

I need to design a robotic vehicle which should carry 20kg of weight and speed of 500 rpm.can you recommend me the geared dc motor to choose.how torque is calculated ?

7. krushna

I want to use two dc motors with 12 v battery should i go both for 12 or use 6

• Coleman Benson

@krushna The battery pack you choose should ideally correspond to the motor’s nominal voltage (greatest efficiency). If your motors are 12V, then choose an 11.1V LiPo or 12V NiMh / lead-acid.

8. Dinesh kumar

I tried 0.4v salt water battery, and I used toy car DC motor , I was measured multimeter 8 to 10 amps but did not run this motor, what can I do ? How to run the motor , which is the problem , please replay me . Thank you.

9. Diego

Hi, i’m searching on the internet for the differences between stall current and rated current, i mean, the relation between them. I’m thinking about buying this one http://www.aliexpress.com/item/1PCS-24V-DC-200-RPM-Replacement-High-Torque-Gear-Box-Speed-Control-Motor/32294661284.html , but I can’t figure out it’s maximum current so I can know better the driver I’ll be needing , cause , I thought about using the L298, and It only allow 2A per motor. By the way, Excellent post! I hope I was clear with my doubt.

• Coleman Benson

@Diego Assuming they use the term “rated” the same way between values, the “rated current” would be the current consumed at the “rated load”. As such, a motor controller which could provide 24V and 2A might be fine.

10. Jack

Hi, I am confused about following terms: “Max. continuous current”, “rated current”. Are they the same? if Max. continuous current is the rated current, why it is much more larger than the no-load current.

Many thanks.

• Coleman Benson

@jack “Max. continuous current” is the current required at the maximum rated load (which should be less than the stall current). “Rated current” may mean the current at maximum efficiency (which would not be the same as the current at maximum load and would likely be lower). Normally you would not find both on the same spec sheet. “No load current” is when there is nothing connected to the output shaft of the motor, while “stall current” is when the motor is prevented from moving.

11. Raffael

Hi,
When I read a value from a motor datasheet e.g. “Nominal current (max. continuous current)” = 2A does that mean I have a range of 2A ([0A,2A]) or is the range [-2A,2A] ?
Another question: I have a brushless EC motor, with a driver that sais input voltage = ±10 VDC (differential). Am I correct that the EC motor uses DC as an input so I can use the whole 20VDC range?
Many Thanks

• Coleman Benson

@Raffael The current would be up to 2A under normal load. It is rare you will ever see a negative current in robotics. “EC” normally means “brushless” and in mobile robot applications, this is always DC voltage. The input would be 10V (not 20V); ± normally means you can connect the wires either way.

12. Raffael

So the thing is, I would somehow need to tell the motor in which direction to turn. I wanted to do this with negative current for one and positive current for the other direction. I have the motor in current mode. It works like that with the custom software for the motor driver. However, I want to control the motor through Matlab Simulink Realtime and thus need the conversion from the input voltage (maximum 10V ) to the current for the motor (max 2A).
So can I input in the range [-5V,5V] which get converted to [-2A,2A] or would it then be [-1A,1A]? Or did I completely misunderstand your answer?
Thank you.

• Coleman Benson

@Raffael Can you submit a new topic via the RobotShop Forum and provide links to the products you are using?

13. paa

please please I am finding it difficult to determine the specification of a DC motor that has been used for a solar water pump project , please can you help out? “” heinzmann D-79677 schonau Gmbh and co.KG tel 490767382080 fax490767382008199 typl 120-2NFB-65 u 30 VDC HZM-Nh712-00-397-00 p 25,9 w m215 Ncm S-nr 0810 276655 I 1.0 A Ausf. 22-50 n990 1/min””

• Coleman Benson

@paa It seeems the motor has all of the specifications printed on the label: 30VDC, 25.9W, 1.0A current and can provide 215N-cm or torque. Not sure about the RPM though.

14. paa

thank you very much I really appreciate your help , please I will like to know if there can be a voltage operating range for this motor , that is , I know the max voltage is 30v and I want to know is there any minimum voltage at which it can not work ?

• Coleman Benson

@ppa If the specs don’t indicate the voltage range, you’d really need to contact the manufacturer.

15. tozz88

Great article. I have looked at several motors with optical encoders built in. They often describe the encoder resolution as “pulses per minute”. I assume they mean the measure of angle not time. However that means a motor with “2 pulses per minute” would have 2*60*360=43200 pulses! That sounds way too high.

• Coleman Benson

@tozz88 If the units are pulses per minute, they likely mean just that (not angle). Most are pulses per rotation (PPR).

16. ashutosh

Can I operate air blower fan with 12 volt,17000 rpm robotic motor

• Coleman Benson

@ashutosh Do you mean retrofitting an existing blower with a new motor?

17. raji

im using dc brushless motor(model no.ffb1212ehe) with an arduino uno for speed control.the motor is running well above 100 speed,but its not running when i give the speed level below 100.can anyone send me the coding??
Thanks……

• Coleman Benson

@raji Without knowing which motor controller you are using, we cannot really help in this regard. We suggest creating a new topic on the RobotShop forum and provide as much information about the products you are using as possible.

18. Marko

Hi Coleman, I am trying to operate a small DC motor but I don’t have much power to work with. I can regulate a voltage to operate near the motor’s nominal voltage, however the motor may not pull as much current as it might want to. Would this make the propeller on the motor terribly inefficient?

• Coleman Benson

@Marko The motor may want to draw as much as it can, to the point that your electronics may be fried. It’s always best to choose electronics / motor controller which can provide MORE than what the motor will need.

19. Ganesh

Hi Coleman am from computer science department and trying to develop dc motor simulator application. It is brushed dc motor with three poles. I want to know how to calculate the current drawn when some weight is added on to the motor and what are the other parameters that are affected.
Thank you.

• Coleman Benson

@Ganesh You’ll need some basic stats about the motor itself, otherwise it’s all guesswork. Most motor manufacturers test their motors physically to be able to get the torque (vs current) and speed (vs voltage) curves, though to a small extent they can estimate what it will be before they produce the motor.

20. ramil

Can you please tell me how will i know if the motor is a high current? sorry for my question.

• Coleman Benson

@ramil You should be able to know based on the manufacturer’s specifications for that motor. If you cannot find any details, base yourself off the power rating. If you still do not have a power rating, large motors = higher current.

21. LasheenGamer

Hey guys,

I am willing to overvoltage the current motor (DCPM motor Class F, 12V, 29A, 250W, 3300rpm) .. to (18V) .. so as I can get more power ..

My question is: How to calculate the new power?

I think If I can calculate the new power and measure the new RPM, I can get the new torque .. That’s why I am asking about the new power ..

• Coleman Benson

@LasheenGamer Motors have specific characteristic curves (example RPM vs. voltage and torque vs. current, and most important, efficiency). It’s best to consult with the manufacturer.

22. Khalid Ali

Hi Coleman, I work for an oil company in Tanzania. Recently we replaced a 3 phase motor pumping heavy fuel oil to the laoding gantry with a CMG 3 phase motor type: CGM 3 160L with a bonfiglioli reduction gear with ratio 9.8 but the flow rate at the loading gantry was significantly reduced. The initial motor’s ratio was 2,3 and was working fone. would you kindly suggest any solutions or causes of the reduce flow rate? Thank you.

• Coleman Benson

@Khalid Ali Unfortunately those are motors which we are entirely unfamiliar with. You need to figure out the torque and RPM from the previous motor and compare it to that of the new motor. It sounds like the pump itself remained unchanged.

23. Ankit Satasiya

im using 4kg 1.5ft long and 30mm wide blade as a horizontal spinner weapon and motor for this weapon is pmdc motor soo…. now for beating 55kg of robot what should be my motor torque and blade rpm and motor rpm and watt ratting of motor pls give figure

• Coleman Benson

@Ankit Satasiya This is beyond the score of the Drive Motor Sizing Tool since the motor is not being used to propel a robot but rather as a weapon. The equations needed are quire different.

24. Ankit Satasiya

and one one another question if weight of my robot is 55kg and i using two driving wheel and my motor is pmdc motor so pls give me apporoxi specification required for motor torque, motor rpm and main is watt rating of my motor. give me sum no.pls

• Coleman Benson

@Gaurav The “rated torque” is normally the maximum continuous torque which a motor can provide. The maximum torque might be reference to the torque it can support but for short periods and is closer to the torque as max power. This is still below the locked shaft / stall torque.

25. dhandapani

I am a farmer I am trying to make high pressure tree sprayer by a 12v dc water pump. for my own use. I am interested in some home made projects. it is my hobby. which specification motor is suitable for my sprayer. I read all your helpfull explainations.thanks.

• Coleman Benson

@dhandapani We suggest that you save yourself some time and troubleshooting and purchase a water pump, and simply assemble the tubing and system around it. Unfortunately RobotShop does not sell pumps for that type of application.

26. Datta

Hi Coleman,
I want to find out the bending strength of pinion and gear for choosing the material. Could you please tell me which torque value i have to take into consideration stall torque or nominal torque of the motor.

• Coleman Benson

@Datta; if you’re looking at material properties, the torque would be “worst case”, so above the stall value.

27. Sharan

Hiii coleman,
i need a DC motor for the load of 25kg. what would be the rating?? and how should i calculate it??

28. kishen

I need to design a Brushless DC motor for 250W , how do I design the stator resistance, inductance ,torque etc. For an rpm of 1000

29. Dipen chhetry

i want make high powerful dron which can fly 10hours speed 500km/hr so i need more energy battery and light fowerful motors so i need your help

• Coleman Benson

@Dipen chhetry You are esssentially looking to create a fighter jet. Unfortunately we cannot provide any support for this.

30. Jins

What will be the tolerance level of 12V,900RPM DC motor. How can I calculate this?

• Coleman Benson

@Jins What ydo you mean by “tolerance level”?

31. Junaid Sayed

Hello Coleman ,
I want to select a DC motor which is suitable for a conveyor belt.
I tried a DC motor that is used in robotics but in vain. It gets very hot.
So please suggest me a Motor that can be used for the purpose of running a conveyor belt which is around 5m in length.
The motor should work on 24V supply

Thank You.

• Coleman Benson

@Junaid Sayed It sounds like your application is industrial and as such you might want to look at more industrial type motors which are meant to work for extended periods of time. Most of the DC motors we carry have a duty cycle of 25% and running them for extended periods will cause them to heat up – which is what you have experienced.

32. Junaid Sayed

Thanks for the reply Coleman!!! 🙂
Actually I need the motor for my Project which is based on Automation.
So i just want to run it for about a minute or so.
I dont want to use it for long duration.
The reason I want to use a DC motor instead of Industrial one is the cost.
Please suggest me some DC motors which works on 24V and have high torque so that atleast I can start researching about them.

Thank you.

33. Dens Dennis

Do solar panel can provide sufficient power for dc brushless motor to run??

• Coleman Benson

@Dens Dennis Solar panels are used to power entire cities, so there’s guaranteed to be a size and power of solar panel to power just about anything, including brushless motors.

34. MRahman

Hi, I am designing a boat driven by DC motor. How to determine the power and rpm for a boat with a pay load of 100 Kg (including battery pack) to get a maximum speed of 8-10 knots. can you please help me?
thanks

• Coleman Benson

@MRahman Good question; we have not done the research for water-based propulsion, so perhaps someone from the community may offer some ideas.

35. Aijaz Ali

Hello Sir,
I am making an Electric bicycle and I have a 22V, 300W, 2900rpm dc motor.
Please tell me how much rating of battery is required to push a load of about 120kg and also to produce high starting torque?

• Coleman Benson

@Aijaz Ali We suggest a 22.2V LiPo battery with high capacity and high discharge rating. At 300W, the motor should consume around 13.5A. The capacity depends on how long you want the bike to operate (the higher the capacity, the heavier the battery). Take a look online to get an idea of the capacity of batteries used in existing electric bikes.

36. Kalina

If I pick two drive motors for a robot that weighs 50lb and attach the motors straight onto the wheels how can I tell if the weight of the robot applied to the motor shaft won’t damage the gearing inside? Do the motors come with a spec that identifies how much weight they can support? Thank You.

• Coleman Benson

@Kalina Only some gear motors provide the radial load which the shaft can support, but a rule of thumb – don’t overload it because it’s likely to be only supported by one ball bearing inside the gearbox.

37. SUNIL kUMAR MANDAL

I AM DOING FIVE LEVEL ELEVATOR SYTEM…. IN ORDER TO LOFT MY ELEVATOR WHICH MOTOR SHOULD I USE?? DO I NEED MOTOR DIVER?? IF SO THEN WHY ?? AND ONE MORE THING, I AM USING PLC .AND HOW TO CHOSE THE MOTOR AGAINST THE WEIGHT OF THE LIFT I AM USING??

• Coleman Benson

@SUNIL kUMAR MANDAL If you mean a real elevator which carries people, that is beyond the scope of this article.

38. dheeraj

how can i choose correct propeller motor combination for required thrust generation..pls help me with this..btw, gr8 article ..really helped

Hi sir..
How we come to calculate the torque and speed of 1hp 1750rpm PMDC motor which is running any vehicle of say 200kg, 300kg..?

40. santhosh

hi sir…..
I am an engineering student.and iam do a project is related to harwester machine run with DC power source
it carry the load of 300 kg so which motor is preferable for this. please give guide lines……
And it work for long time .And also give about battery specifications also…….

41. Movin Perera

Hi!
I purchased 4 1.5A DC motors and a powerpack of 1200mA output current.
Please tell me what to do!

• Coleman Benson

@Movin Perera There are many factors involved in getting a mobile robot to move. We suggest creating a new topic on the RobotShop forum and providing as many details about your project and the parts you are using.

42. saud

I want to build a white board eraser by using bluetooth through arduino uno r3 so firstly which motor should i use to get my work done
otor has to take load of 4kg
Please let me know the specification of motor best fitted for my project
N secondly how to program it to get the work done
Plz let me know as early as possible

• Coleman Benson

@saud Unfortunately your question is much more conceptual. Please post a new topic on the RobotShop forum. We also encourage you to create a drawing of how you think the setup will work.

43. Vinay kumar

I am doing my Engineering project in which Motor selection became an big hectic for me, My project is to Close an waterproof sheild automatically whenever an rain is detected by Rain sensor. i am doing the project model in the size of Average table(approx 4 feet).
I want a motor which can take load upto 2 or 3 kgs and rotate for 90 degrees clock wise and then rotate back to its initial position. Please sagest me motor with specifications, (Many said me to go for Servo motor), please specify the model of motor.

• Coleman Benson

@inay kumar Since your question is more design oriented, please create a new topic on the RobotShop Forum and we would be happy to help you there.

• Coleman Benson

@yathi Not sure what answer you are looking for – you are asking what the delay would be between the time the wires are powered versus when you see motion?

44. nikhil

i want motor such that it should bear a load of 300 kg. and my speed requirement is 5 km/hr. how much power is required? if i select maximum 100 rpm after load

• Coleman Benson

@nikhil 300Kg is a force rather than a torque. For more design or concept related questions, can you create a new topic on the RobotShop Forum and provide as many details as possible?

45. dan

Hello, hope this request fits here into “How to Interpret” DC Motors Specifications. I found specifications for Pulsed, Brushless DC Motors (these are PPM or PWM speed-controlled RC motors) and would like to understand their following specifications (spec table, below, itemized) and their spec meaning. For instance (#3) what is the KV, how to interpret it? Or (#22) Sensored? what kind of sensor, thermal, RPM, etc?
1) RC 30P-Flash-AA-8150KV; 2) TURNS 4.5T; 3) KV 8150KV 4) Rotor ￠7.2*￠12.8mm; 5) Pole 2poles; 6) Watts 490; 7) LIPO (1-2Slipo); 8) Max Amp(60S) 108A; 9) Max RPM 50000; 10) Length 52.3mm; 11) Diameter ￠36mm; 12) Size 540; 13) Weight(g) 165; 14) Shaft Diameter (inches) ￠3.175mm; 15) Length of extend shaft 12.7mm; 16) Meet IFMAR rules Y; 17) Sintered Rotor Magnet Y; 18) stepless timing adjustment Y; 19) Thermal Protection Y; 20) Hand Wound Y; 21) Suitable（ESC） TORO TS 120A ESC ; 22) Specification Sensored TS120A ESC

Thank you

• Coleman Benson

@dan We agree that it is a good idea to add brushless motor spec interpretation, but for the moment we have other priorities. For brushless motors, you can get some ideas from the following article as they pertain to drones: http://www.robotshop.com/blog/en/make-uav-lesson-3-propulsion-14785
Note for the sake of minimizing the length of the comments section, we have removed the specifics of the motor from your comment.

46. elliott

Hi, if I want to generate an instantaneous high output power for DC brush motors with nominal voltage 24V, what would you suggest?
Is it feasible to provide 48V in a short time for the motor?

• Coleman Benson

@elliott It will come down to the current, as well as the motor’s tolerance to this current. A big advantage to electric motors over gasoline is that they can produce almost instantaneous torque (one of the reasons why the Tesla automobile has such impressive acceleration).

47. prasanna

Hi, I want to know the starting current of a 48v 500W dc brushed motor, In the specifications of motor there is no starting current specification.

• Coleman Benson

@prasanna It is best to contact the manufacturer, and will depend on many factors including the load and the propeller used.

48. Abhishek

Hi, just to be clear if a motor has a holding torque rating of 10Nm it means it can hold a 10kg weight at the end of a 1m arm horizontally? Similarly a holding torque of 1Ncm means it can hold a one kg weight 1 cm away from its center?

• Coleman Benson

@Abhishek Normally holding torque is associated with servo motors, so yes, that would be the torque it can support (10Kg-cm can be 1Kg at the end of 10cm for example, or 10Kg at 1cm). 1Kg = ~10N.

49. kiran

Will u please tell me that 200kg of boat In water how much torque is required for dc12v motor

• Coleman Benson

@kiran The calculations needed to determine the motor specs for a DC motor used to turn a propeller and move a boat are beyond the scope of this article.

50. Sujit

Hi this interesting. A couple of questions I have are about the best DC micro motor for using with a peltier module. Since the real TEG modules are very expensive, I want to use the simple TEC module to generate a current. The TEC module isn’t going to be very efficient in power generation. So my question are:

1. What is the best (also cost effective) DC motor that is to be chosen……would it be the 1-6v motor, as opposed to the 3-6v motor.

2. This is about the type of motor. I see that there are motors that are marked as ‘solar’ on EBay. These I assume are intended to be connected to solar cells. Then there are the traditional toy motors with the regular magnets and armature. Also some motors marked a scoreless. Which of these do you think would best work for a low out put generator, such as the TEC module?

Thanks

• Coleman Benson

@Sujit Normal brushed / coreless DC motors don’t have any specs for when they are operated in reverse and used as generators. In most cases it’s very inefficient. You might try searching online for “micro generator”.

51. tausif

Hi.i just want to kno that my project deals with solar module..where m mking solar based grass cutter….for which m using a solar panel,6v 2 batteries,…..i just want to kno which dc motor i should use to get high torque..in short specification..

Sir I want 100-220 Nm torque from dc motor to open and fit nut of car wheel so plz suggest me smallest possible size motor and its other apecification like voltage, power, rpm. My main aim is to get required torque in small size motor. Thanks

53. Mike

Hi, I have a 24VDC 500W 2800rpm rated motor I am over volting with a Lithium-ion battery pack, (rated voltage 36V, max voltage 41V), how do I calculate the power this motor will produce at the increased voltage? Please note, an approximate value would be fine, the motor has been modified with better air flow through and an added cooling fan to help cope with the extra heat and contacting the manufacturer is not possible in this case. Thanks, any help you can offer would be greatly appreciated.

• Coleman Benson

@Mike To our knowledge, it would come down to the motor curve, which would be based on testing. You can use a multimeter to read the current and multiply it by the applied voltage. Note that the efficiency will likely be suffering.

54. Abhishek

Sir I’m working on a power generation project so for that I’m little confused about which motor should I select for power generation. My rpm varies from 100-300 rpm. So I’m planing for a 500 rpm DC motor but the thing is which one would be better geared DC motor or non geared DC motor?
Thank you 🙂

• Coleman Benson

@Abhishek Unfortunately we don’t carry many generators, and the DC motors we offer do not provide any details regarding their power generating capability. We suggest looking for a motor which is specifically made to be used as a generator.

55. Cena

What happens if we connect a toy motor to a 7.2V battery???????

• Coleman Benson

@Cena Ideally the motor should be rated around 7.2V (for example between 6V and 9V). When you connect it drectly to a battery, it should spin in one direction.

56. Pratik

I am making tracked robot for that I am using wheels of diameter 10cm.for that I wanna use 12 v DC motor 100rpm my robot weight is 7kg.so how much torque DC motor I choose?

57. Rick

Which 12 v DC motor I select for robot which has weight of 8kg .wheel diameter 10 cm.how much torque?

58. Lakmal

Hi how can i make 1.2 volt without battery, thanks

• Coleman Benson

@Lakmal You would need a different method (alternative energy), for example a solar panel, hydro generator etc. Alternatively, you can even generate a potential difference using potatoes or lemons.

• Coleman Benson

@Omar That will depend on the gear ratio and motor characteristics.

59. Duane Evenson

Correction: 1kg * 1m/(s^2) = 1N (the acceleration is 1, not 9.81)

• Coleman Benson

@Duane Evenson Converting Kilograms to Newtons?

60. Matt

I am looking to make a robot that will ride on two treads that will carry about 150 lbs maximum. I am looking to see what would be the lowest specs/cheapest motors that I could purchase to accomplish this.

61. Jeff Yoo

Let’s assume that I have a motor which possess stall torque 76.13oz-in (5482g-cm). If the load possesses the mass of 800 g (let’s say the wheel attached/connected to the shaft of the motor), then there must not be problem (unless the current is very low). Is my assumption correct?

62. Sukanya

I want to know the actual torque of 300rpm motor

• Coleman Benson

@Sukanya The RPM has no relation to the torque.

63. Ram

Hello all,

I am using a BLDC motor and I am using SMPS output of 24V power supply which is given to my controller baord and it converts it into 5V. My motor is running perfectly with rpm of 320 but the prblem is that the current is 1.5 amp. But I need current as 1 amp for my this project. How to do it? Awaiting for your reply.

• Coleman Benson

@Ram If a motor requires a certain current, it is quite hard to limit that.

64. jesse

I’m planning on using 3 batteries in a series as a power supply. They are rated each rated @ (8v 20ah cap 165 [email protected] 121). The DC motor I’m planning to use is a p.m.d.c (24v DC 30a output 500w class a ao) my concern is the the amps when a heavy load is used. My question is there any electrical componets I can add to my circuit other then a breaker and a switch.

• Coleman Benson

@jesse A fuse (which you may mean when you say breaker) is the best option.

65. Jerwin Prabu A

Kindly help our product. Actually we need a hub motor for Running a robot wheel. Hub motor required if 10 ​inch diameter.Torque 15​ ​Nm each. Power 24V/48V, On load torque around 200 kg cm​. We need to add gears.. Possibly planetary gears to reduce speed to desired range. With these specs the RPM will be high, but when we add gears it will be reduced. This is the accurate specifications. I would like to know the availability of the hub motor ? It it will give best solution or not ? what about your suggestions ?

• Coleman Benson

@Jerwin Prabu A Unfortunately we do not offer any hub motors at this time. We will take your request into consideration when looking for new products / suppliers to enter.

66. deepak

how to calculate load details of a particular motor? For example I have a motor 12V DC wiper motor, may be 32 RPM.

• Sébastien Parent-Charette

@deepak: If you do not have access to the specifications of the motor in question (such as a datasheet from the manufacturer), you would have to setup a test bench to determine no-load RPM, no-load current, stall torque, stall current, etc. Of course, this is not a trivial thing to make and requires experience in many fields, such as electronics, programming and mechanical engineering.

• Simon Latour

@Vlad The stall current it the current required to achieve stall Torque. If you wish to drive the motor to its stall torque value, you will need 20 amps. Be careful though as the motor will burn pretty rapidly at those values. Stall torque is an absolute limit and motors should never be operated at those values. For example, if you need 680 Oz-in of torque in your application, you should search for a motor with a rated load of 680 Oz-in, not a stall torque of 680 Oz-in.

67. Sherif Thomas

I’m considering a BLDC motor for my project but having a problem calculating the proper battery capacity to use. The reason is the the motor specs states (125 amps AC and 180 amps DC into the motor controller).
Is this motor consuming the 125 amps or the 180 amps?

• Eric Nantel

@Sherif Thomas, It will do both, but the power source from the AC side is not the same as the DC side. The controller must use AC to work so we do not think it will work from of a battery pack.

68. zeeshan

can u please tell me the power rating and efficiency of a 24 volts motor and 10A current…rpm is 115???

• Eric Nantel

@zeeshan, There are various calculators available online that can help you calculate this. (Example)

• Coleman Benson

@bobya Can you use Google Translate (Hindi to English)?

69. Venkatesh

Sir. We are proposing to use a PMDC motor of 40 W capacity ( Nominal values – 24 V DC,2.3 A, 10 Ncm ,3600 RPM, Stall values – 67 Ncm, ), with a 100 : 1 gear box, to lift a load of 40 KG over a roller of 100 mm diameter.

Once the load if lifted up to the maximum height say 5 to 6M, it will remain there ever, (24 x 7 x 365 days) by applying a holding voltage of 4 V instead of 24 V.
What are the precautions , I should consider, and what will be the holding current . How the find the temperature increase. Please help

• Coleman Benson

@Venkatesh Rather than constantly powering the motor, you might consider adding an electromechanical brake to the rear shaft – it would be far more efficient and consume a lot less current.

70. Beena

Sir we need to calculate Rpm of 5V DC motor. For this we are using 20 slot encoder disc. Can you please help us to correct the formula: rpm = 60*1000/((millis() – timeold)*rpmcount/20);

• Coleman Benson

@Beena That’s unfortunately beyond the scope of this article, but you can find a number of equations online. If you are using Arduino, there are many examples.

71. MEDI

Hi, my question is how the stall torque and continuous torque that a motor can deliver is measured in the factory??? and another question is can you please introduce a user friendly software for me to simulate the magnetic and torque related parameters of a design???
Thanks.

• Coleman Benson

@MEDI The torque at many factories is rated based on the windings, coils etc. They then confirm with tests if the theory matches the actual build. Unfortunately we are not in a position to create such a tool at this time.

72. John Clayton

I am wanting to use a small DC motor to drive a plastic fan blade inside a tube very close to the outer diameter of the fan blade. The motor specs show a nominal voltage of 7.2 VDC at 22,000 RPM under no load conditions drawing 1 amp. It is rated at “6-12 VDC” with RPMs at 18K – 33K RPM. I want to operate the motor with two 3.72 VDC IMR 18650 Lithium batteries in series. The batteries are rated as 2.9 Ah high-drain batteries used for E-cigarettes. They are rechargeable. So the total voltage would be 7.44 VDC. I am concerned that if operated for more than a few seconds these batteries might overheat and, being Lithium, might explode. So, I need a current limiting resistor. I can calculate that E/I=R So 7.44/1= 7.44 ohms. But, with a load of the fan blade blowing air through a smaller tube will probably increase the current draw of the motor. The batteries are rated at 2.9 Amps for 1 hour (2900 mAh) and specify a discharge current of 35 amps. So, I plan to limit the current to ???? The motor specs do not show MAXIMUM current. I want to create a small battery powered device that replaces canned air for blowing out keybards and other small places that contain paper dust. So the output tube will go from a 1″ fan to a 1/4″ tube, I suppose. what do you suspect I will come up against? I feel I know just enough to get me into trouble. Thank you for any comments.

• Coleman Benson

@John Clayton The post is far too long to answer in the comments section of a blog – can you please create a new topic on the RobotShop Forum? We would be happy to answer you there.

73. Travis

Coleman,

After reading most of these posts here, I must say that you have the patience of a saint..

• Coleman Benson

@Travis Appreciated. It’s not always the easiest to get started in robotics, so we do our best to help and provide information and answers.

74. MEDI

i know what the nominal and stall current are, my question is suppose that i want to design a 3A motor(nominal current), how should i do that? is it just related to winding specs??? i mean that if i have a winding made of wire which is capable of holding 3A continuously, could i say that i have a 3A motor? and if yes, then how the stall current should be measured?

• Coleman Benson

@MEDI That’s actually a level of support / knowledge beyond what we can provide here as it pertains to the specifics of DC motor construction (number of coils, coil diameter, material used etc.). Normally when you refer to a motor, it’s in terms of maximum power (watts). Stall current can be measured (rather than theorized) simply by stalling the motor for a fraction of a second (but ideally not long enough to cause damage).

75. Ravi Shanker

PMDC motor..5 Hp. how much maximum power can be achieved regularly?

• Coleman Benson

@Ravi Shanker That really depends on the motor, but if it’s rated at 0.5 horsepower, then that’s the rated continuous power output.

76. Taha

Sir can u plz help me in deciding a power input of 2 dc motor.. actually i made a Rc car. Which is not running good under load. M uasing 9v battery to drive 2 dc motors

• Coleman Benson

@Taha A 9V alkaline or NiMh battery is not useful for powering a mobile robot; you need a battery pack whose voltage is similar to that of the rated voltage of your motors, and then choose a capacity which will help the robot last long enough between charges.

77. Sam

Hi Coleman,
I want to bench test a small 12V elec motor/gearbox combo to see if it is working condition. I have been given the following values by the manufacturer
Nominal current (max. continuous current) 0.299 A
Stall current 2.24 A
The lowest 12V power supply I have on hand right now is 410mA. I also have a 1A and 2A power supply available. Would this 410mA power supply be okay to test the motor or would it burn it out? Cheers

• Coleman Benson

@Sam 0.41A is “ok” if the motor will consume only around 0.3A under load. A 2A supply is much better. Note that the motor will only consume as much as it needs and the power supply will only provide as much as is demanded.. up to the max current rating.

78. kiarash

hi coleman
i want to build a device that Interpret DC Motor Specifications for me specially motors under 0.5 hp and i dont know where to begin and i will be grateful if u can give me some pointers and help ty

• Coleman Benson

@kiarash What input would a user enter, and what output would the tool provide?

79. kalif nico

the site is so intresting ,what is the RPM of a winch motor

• Coleman Benson

@kalif nico It would be in the specs of the motor. Take a look online at a few commercial winch motors to get an average RPM.

80. Linus

please sir, i want to select a 12V DC motor for an electric lawn mower. please can u help me in selecting the motor ratings.

• Coleman Benson

@Linus That is the point of this tool – please enter the information you know or guess.

81. yashwant

i have small 12v dc motor, but the current and torque rating is not mentioned, please let me now how to calculate current rating at no load ?

• Coleman Benson

@yashwant We are not aware of any “easy” way – you’ll need to develop a torque – current curve, as well as an RPM – voltage curve based on testing.

82. Banji O. I

I want to generate power of 2. 5kw, sir which dc motor I should use and what should be the specification of the dc motor. I shall be glad if you respond to this.

• Coleman Benson

@Banji O. I “Power” relates to voltage and current; you normally choose a motor not based on power, but rather on torque, nominal voltage and RPM.

83. juliano

Hi.

I have a motor which is 3V and 5RPM.
My question is related to TORQUE. is it associated to voltage?

Fo example using it with 3V or 5V does that change the torque (N*m) ?

thank you

• Coleman Benson

@juliano The torque is somewhat affected by voltage, but not as significantly as gearing. Normally you should choose a gear motor based on torque, nominal voltage and RPM. Increasing from 3-5V would increase the RPM: over a range of voltages, the relationship between RPM and voltage is linear, and the relationship is provided as a value “Kv”. The relationship for torque is “Kt” and relates to current.

84. Nasir

How can identify a motor, is it DC motor or AC motor, where specification plate is not available ???

• Coleman Benson

@Nasir The application / power supply can give you a good idea – is it battery operated? If so, it’s likely DC. Does it use a wall adapter which converts AC to DC? If so, then it’s likely DC. Does it have 2 wires? Most DC motors have two wires (would be another hint). Is it used in an industrial application (for example on a large machine)? It might be AC.. so further research needed.

85. Ed F

If I am using a motor at the ‘rated torque’, which is stated on the specification sheet as half the stall torque, how can I run this intermittently, and how many cycles will it run (obviously I have no thermal information or windings info)? Can this be said that if you are running it at the ‘rated load’ that you can run it continuously, and intermittent will also be fine?

• Coleman Benson

@Ed F The rated torque does not provide for a 100% duty cycle; it may either be the torque at maximum efficiency or (less likely) the torque at maximum power. If it’s a DC motor, the greatest duty cycle would be achieved when the motor is operated at maximum efficiency (for lowest heat loss). It all comes down to heat buildup which varie based on torque, voltage and how long it is used.

86. MOHIT

sir, i am a engineering student and i am making a project on HOVERBOARD , i want the specification of the DC motor which can bear the weight of 80-100 kg with maximum speed of 10-15km/hr. and work for 2-3 hours. please give the specification of battery (volts and mAh).
i have seen a video on youtube in which specification of motor was given 12V ,300 rpm but torque and load bearing and battery specification was not given . please help me sir as ihave to submit my project on 23 sep. . email- [email protected]

87. MOHIT

SIR , i am making hoverboard .i am using 12v 300rpm,23kgfcm motor and a battery of 12v 7Ah , will it bear the load of 70kg ,if not then by increasing battery to 12v 12 Ah will do so. i am unable to get a high torque motor .

• Coleman Benson

@MOHIT Do you mean a hoverboard similar to a Segway without the handle (one wheel on either side?) If so, then the power should be split between two motors, not just one. Additionally, the weight of the passenger and robot should not be directly on the motor’s output shaft unless it’s very well supported.

88. Shreyas Bhagwate

Hi Sir, I am doing 1 project in which I need a DC motor to sustain load of min 100 gm & max upto 300 gm. Also, I want to control its speed and measure the Voltage & current. Please let me know if you want any more details and support me in the same.

89. shrut

hii sir, i m working on a project in which there is a req of dc motor which can lift 250 gm load . also i want to controll the speed of motor and monitor the readings on oscilloscope plz give me direction regarding the same.thank you..

• Coleman Benson

@shrut A DC motor provides “torque” as opposed to “force”. Torque is measured as force multiplied by distance. You control speed and direction of a DC motor with a DC motor controller. What do you want to monitor?

90. shrut

I want to monitor current & voltage. Also I want to control the speed of motor. Please provide formula to calculate motor rating suitable for the 100 – 300 grams of load.

92. Angelos

6-9 DC motor heavy duty, max amp 4.7. What kind of ac/dc converter should I use??? I tried a 6v 5 amp but nearly distroyed my project…

• Coleman Benson

@Angelos Why are you using a regulator at all? You should use a 6-9V DC power supply or battery capable of 5A or more. If it consumed 5A, that likely means the motor cannot provide enough torque for your application.

93. Mohan

i have 20KW bldc motor ?? how do i find the right battery for my motor?

• Coleman Benson

@Mohan You need to know the operating voltage range of the motor as well as the nominal voltage. Dividing the power by the voltage will give you your peak current. The voltage will determine the voltage of your battery pack, while the current will determine the requirements for the capacity and required continuous discharge rating.

95. Jonathan

Coleman, I need a little help. I have a static (plastic) model that I am trying to give a more alive look. I have want to install a dc motor inside the engine to turn a metal prop, 4 blade 18cm and weight 100gm. I need it to turn reasonably convincing from slow start up to running…. not too fast or I’ll have a kit again. The prop is also not balanced so another reason to be mindful of not too fast. I only have a small space H(1.5cm) x width (2cm) and depth 4cm… I am struggling to interpret what DC motor I could use that won’t either struggle and burn out or leave me with a kit. What sort of torque or rated load should I look at, please?

96. Ujjwal

I want to ask what specs of the motor do i need to generate a torque of5kg cm

• Coleman Benson

@Ujjwal The motor’s torque should be specified in its datasheet.

97. Vimal

Hi…

I am planning to buy a treadmill. The shop manager said to me, treadmill uses 120 watts dc motor with 1.5 hp. Is it true? I need low power consumption equipment. Because,already our bill is around 2000. Please help me..

• Coleman Benson

@Vimal 120W converts to around 0.16 horsepower. The power consumption will related to the speed; it should not always be consuming high current. Consider that a normal light bulb is 60W, so a full motor consuming the same power as two light bulbs is pretty good.

98. max

Hi,
i bought a motor and the datasheet that came with it says:-
50:1 Gear ratio
260 rpm @ 6V
40mA @ 6V
360mA stall current @ 6V
10 oz inches torque @ 6V

i have a few questions:
1-how can i calculate the stall torque
2-what is the 10 oz inch torque given
3-how can i calculate the motor constants -namely Kt,Ke and electrical Resistance of the motor

• Coleman Benson

@max 1) The stall torque is normally provided; the 10 oz-in may be either the maximum continuous rotation or the stall; you should contact the place where you purchased the motor to clarify, or check the spec sheet 2) See previous reply 3) Normally these are provided. If not, they would ideally need to be tested.

99. Srikanth

I know only how much load is to applied to my experiment i.e, Cantilever beam subjected to an forced vibration,when an motor is placed at one end and the shaft is connected to a disc, for this disc an eccentric mass is added. The approximate load on shaft is 5kg i.e around 50N, so can I get the information what type of motor should be used for this condition, & what may be the minimum speed required to rotate the shaft at that loading condition

• Coleman Benson

@Srikanth Since your question is more design related, can you create a new topic on the RobotShop Forum under “actuators” and perhaps provide a drawing of the setup and what you would like the actuator to do?

100. avs

my question is regarding vacuum pump. suppose a 12V dc vacuum pump is used to take out air from bag, how much of volt battery and how many do i need?

• Coleman Benson

@avs An air pump usually has a rating in cubic feet of air per minute (at a rated voltage). If not, you’ll need to know the rated voltage and test how fast it can evacuate air.

101. Suwarna

i tried to use four 150 rpm dc motors via 12V,500 mA dc adapter but it’s not working.Please suggest the correct way.

102. shaera

hai im currently doing my final year project need your guide on selecting 12v dc motor wattage so that it be able to move my load 5kg(max) forward and reverse that will be controlled by my microcontroller

103. Dhiraj

I used a motor from electro kit whose imput current is not mentioned shall i test it with 12 v adapter reply fast

• Coleman Benson

@Dhiraj If you are not sure what the input voltage is, and cannot find it anywhere (even after contacting the manufacturer), then it’s best to start low at 6V.

104. Jemes

I want to use small 12 Volt DC motor with gear combination to make a jig to lift-up 2 tons. What is your recommendation? Do I need to get right matching of gear combination? If yes please help me to calculate the correct data. Thanks. Jemes

• Coleman Benson

@Jemes Two tons is essentially the weight of a normal car – you need a powerful winch system for that with very heavy duty gears. The speed will be very slow and the current will likely be very high. For more help, please create a new topic on the RobotShop Forum, but based on the question, the application does not sound very robotic.

105. Dragos

What does it mean of the gear ratio of a DC motor is 120:1. What does 120 and 1 stand for? I understand they are the ratio between the no of teeth, but which gears?

• Coleman Benson

@Dragos The numbers represent the gear ratio, in this case the gears act to reduce the speed by a factor of 120 and increase the torque by a factor of 120. There are likely many gears needed to create this ratio.

• Coleman Benson

@Mave The choice of battery depends on the application, as well as the motor, and how long you want the robot to last between charges. Check the maximum continuous current per motor (amps) and then multiply by six to get the discharge current for the battery pack. The capacity relates to how long the robot will last between charges.

looking for a 12 v dc motor to raise my milling machine head which is rack and pinion geared and raised by a hand crank. I would like to couple the shaft with a motor . What should I look for ?? . The milling head weighs 220 lbs,

• Coleman Benson

@CONRAD That’s a very specific application and it sounds like you need an industrial electric winch motor. We do not have anything specific for that application – you’d need to tell us the torque and RPM needed (might try through experimentation).

if 30A is rated value of current give on data plate of DC motor. What does it specify line current or armature current

108. Mike

im trying to look for a motor for my project where i will be designing a aid device to hoist patients from their bed, motor should be able to lift 100 kg, expect the radius of the spindle for winding to be around 3 cm, does that mean that the motor specification i need to look for must be at least able to have a torque of 300 Nm ? the rpm of the motor should be low, choosing a stepper motor with the rating. Am i on the right track ? or are there other option that are cheaper or more efficient ?

109. ALI SAIF UDDIN

Hello,
I have the following motor specifications:
Resistance = 0.016ohm
Max Current = 50A
Max Voltage = 15V
Power = 820W
Kv = 1050 RPM/V
Kt = 0.009095
Using these I need to determine the operating current in order to get the torque of the motor.
Is there an analytical method or do I have to resort to experimental methods.

Thank you

• Coleman Benson

@ALI SAIF UDDIN You have the torque constant Kt which should be in torque (Nm, oz-in etc) over current. This will give you a good idea of the current at a certain torque.

110. jay

hi sir. i have a motor with 3200rpm at no load. if the load is 20kg, what should be the new rpm? thank you

• Coleman Benson

@jay You would need a graph provided by the manufacturer of torque versus RPM. Normally the manufacturer needs to test this and creates a grapho

111. raj

sir, my project is automatic wheelchair, so please suggest me the motors which can push 120kgs of weight.

I am making a car for a project its weight is 17 kg. I am using gear motors in rear wheels of it. Can you please let me know that what torque should my gear motors have? rpm can be low.
Thankyou

113. Manikanta

Sir , my project is electric lawn mower . 3 motors are used in project .1 motor for cutting grass by blades are couple withshaft of that motor .2 motors are used for lawn mover body moving purpose .which type motors are used

114. rashid

I think your footnote on torque is wrong , 1 kg is roughly 10N of force and not 1N

• Coleman Benson

@rashid You are entirely correct. Likely a typo at the time. We have updated it and appreciate that you took the time to tell us.

115. Venkatesan

Hi Coleman, I’ve a 300RPM 12V DC motor and its specifications are as below,
30kgcm torque

I’ll be using a 12v, 28 AH battery, but the load current of DC motor is 7.5 A max. so can I use this battery with the mentioned motor without any damage on motor? and how long this motor can run with one full charge? and can I use this motor to convert my city bike to e-bike? total weight would be 80 kg ( Bike + Person ).

• Coleman Benson

@Venkatesan That’s a really big battery. The motor will only draw the current it needs, so it should be fine.

116. Deep Ode

Which motor shall I choose for my combat robot having 10-12 kg weight. I would be using 4 motors.

i. 4x 200RPM 10kg-cm motors or
ii. 4x 60RPM 15kg-cm motors
It looks like 15kg-cm would be better choice as torque matters in robowars and speed is not really that much of my concern. But I don’t know if 60RPM would be enough to start the robot.

• Coleman Benson

@Deep Ode It’s difficult to determine the “best” motor given the range of conditions which a combat robot will face (being pushed by another robot, traction concerns etc.). We do not have any questions to present to you, but you can follow the guide here and add an additional force (from another robot) to the equations: http://www.robotshop.com/blog/en/drive-motor-sizing-tutorial-3661

117. Cj

Good day sir, we have a project called jar tester(6-paddle stirrer) and i just want to ask what motor you can suggest since we have decided to use dc motor, the output speed required is (25 rpm, 100 rpm, and 250 rpm) ,we are using a belt drive system and we really don’t have idea about electrical components. And also, if i may ask, how can we vary the speed of the dc motor electrically speaking? thanks ahead sir.

118. Usman

What is meaning of rated speed mentioned in most of the datasheets provided by motor companies?

• Coleman Benson

@Usman The “rated speed” tends to be the rotational velocity (in rpm) of the motor when it’s subjected to the “rated load” (torque). Essentially, how fast the motor will turn under normal resistance.

119. Usman

If i want 20 rpm at the output of the motor, when operated with nominal load, should i design the reduction ratio according to no load speed (lets say it is 7000 rpm) or rated speed (lets say it is 5000 rpm).?

• Coleman Benson

@Usman If you want it to rotate at 20rpm, you should really consider using a gear down, not simply lowering the speed of a non-geared DC motor. You would choose based on the rated speed.

120. Joseph

I have a load whose weight is around 500 kilograms, mounted on a circular aluminium rotating platform, like lazy susan. this platform has teeth and will be connected to a worm motor. my question is, I dont need high RPM. 4 – 10 seconds only to rotate 4 degrees is fine. what’s the min torque I need? 30 Nm enough? any other spec of the motor I need to know about? is that enough to also counter the friction aside from the inertial moment of rotation? thanks

• Coleman Benson

@Joseph You will need to do some calculations for friction (static and kinetic) and inertia. There are no “back of the napkin” calculations we can provide.

hello, my question is very simple.. which motor driver is suitable and can support for four motor power window?

• Coleman Benson

@saddam You need to know the specs of the motors (voltage and current) before you can choose a motor controller. Normally these are 12V (because a car battery needs to power them), but range in current consumption (est. 250mA)

122. Joseph

are motors with torque ouput above 50Nm common? are they considered high torque? thanks

• Coleman Benson

@Joseph That would be used for medium sized robots. What is considered “high torque” depends on the application. If you want to make a small mobile robot, 50Nm is high torque.

123. KEZIH

Up to which value I can go for a DC motor for nominal current 110% … 150%, thank you in advance 🙂

• Coleman Benson

@KEZIH Normally current is not described as a percentage. Would 100% be stall? If so, you should only operate at around 25% stall.

124. khazie

how do I calculate the power of a motor given that the speed of motor is 30RPM? Thanks In advance

• Coleman Benson

@khazie You need more than just the speed. Ideally the easiest way to calculate power is Power = current x voltage.

125. Bk

Motor Specifications: Speed (without load): 7820 rpm, Speed / Torque: 7820 rpm / 594 g-cm ,Stall torque: 5596 g-cm ,Current draw (at 7820 rpm): 1.5A ,Nominal voltage: 12 VDC Operating voltage: 6 to 14 V.
Motor driver specs(l298N motor driver): Power Supply 50 V ,Logic Supply Voltage 7 V ,Input and Enable Voltage –0.3 to 7 V ,IO Peak Output Current (each Channel) – Non Repetitive (t = 100µs):3A, –Repetitive (80% on –20% off; ton = 10ms):2.5A, –DC Operation:2 A ,Sensing Voltage –1 to 2.3 V ,Total Power Dissipation (Tcase = 75°C) 25 W.
Can this motor driver be used for the above mentioned Motor?? If so How??
Thank you.

• Coleman Benson

@Bk Your motor is brushed, 12V and 1.5A, so you need to find a DC brushed controller which can provide 12V and 1.5A or more. It seems the L298N can do the trick, but is a little too close to the minimum specs. You should choose a controller which can provide at least 2A, and 5A or more is even better.

126. pankaj sharma

i need to know that what kind of dc motor is to be used to lift 10 kg weight and the size is to be as much as possible

• Coleman Benson

@pankaj sharma There are many ways to lift a weight. We suggest creating a new topic on the RobotShop Forum and describing your application in detail.

127. Shrikanth

I need to do a fast car do I buy geared with torque motor 12v rpm motor please suggest me as soon as possible

• Coleman Benson

@Shrikanth We suggest researching RC cars – almost all use brushless DC motors with a bit of gearing.

128. Shrikanth

Sir I need to build a fast car which motor should I prefer geared or rpm motor

• Coleman Benson

@Shrikanth Research RC cars – almost all use brushless DC motors with just a little gearing.

129. Abhinay kumar

Hi Coleman, I want to install a conveyor having load capacity around 25Kg, what kind of dc motor should i use? conveyor would run through water.

• Coleman Benson

@Abhinay kumar The calculations involved are beyond the scope of this article. You will need to get an idea of the torque and RPM required. Friction will also play an important role in these calculations.

130. Deepak Reddy

HI Coleman, my application requires a DC motor to operate at constant load (torque) and variable speed. Is this possible since speed and torque are inversely proportional. I certainly know that speed can be varied by changing applied voltage. Also, does the value of stall torque change at different voltages.

• Sébastien Parent-Charette

@Deepak Reddy: Yes, it is doable to control a DC motor by torque (instead of speed). You can read some answers on what is torque control here, for example. The voltage, speed, current and load are all related together when trying to control a motor. Of course, such a form of control will require both a position sensor and a current sensor of good quality, measurement speed, etc. We recommend that you find a good control book (maybe one relating specifically to motors or robotics).

131. Deepak Reddy

In my application, I require a DC motor that can operate a fixed load at different speeds. Is this possible? Since torque varies with current and speed varies with voltage, does this mean that voltage has no effect on torque and that the dc motor will generate the same torque even at lower voltage?

• Sébastien Parent-Charette

@Deepak Reddy: As mentioned in our other reply, DC motors voltage, current, speed, torque (and load) are all related to each other electro-mechanically. This is due to how a DC motor is built and functions. We will not go into more details here as this is too complex for a simple blog comment and we strongly recommend that you read more about DC motors. Getting a few engineering books about this would most likely be a good idea. Here is a short explanation of electric motor fundamentals.

132. Prakhar Jain

I am making an acrobot(underactuated double penduIum) wanted to purchase a motor regarding the above.I want 3.2Nm torque at 500 rpm. Which motor should I purchase and should I use a gearbox?

133. Maverick Ng

i have 12v dc motor with 6100 rpm, if i apply 5v input how many is the rpm?

• Coleman Benson

@Maverick Ng It’s likely not a linear relationship that far from the nominal voltage. Some motor manufacturers include a value KV which relates voltage to RPM. The motor may operate far less efficiently at 5V.

134. raj chavan

mr.coleman i m trying to build an electric car its weight is 200 kg…and we are thinking of using dc series motor..but we are confused of what hp and of what voltage that motor shold be..can u plz suggest me..???

• Coleman Benson

@raj chavan That is the weight of a large scooter, or what a normal scooter plus driver weighs. Many of these need 24V, 250W to 500W motors.

135. Rechelle

We will create robot with wheels but this robot can handle 10KG load. We will have two wheels and gear with motor ..
Mr.Coleman do you think dis motor can ? Under are the specifications

Specifications:

Gearbox: Spur Gear
Rated Voltage: 6V (3 to 6V Range)
Rated Current: 380mA
Rated Speed: 65 RPM
Rated Torque: 1.95Kg-cm
Stall Torque: 10Kg-cm
Max Power: 2W
Weight: 100g
>>DC Gear Motor 6V 77RPM – SGM25-370

Hello Coleman! I am doing a thesis related to coreless dc motors. Many manufacturers say that the motor rpm is 50 000 to 60 000 rpm.. is that real? otherwise what is it? because other webpages are saying 10 000 to 20 000 rpm which sounds much more logical… Could you please explain to me, I need help in this. thank you so much!

• Coleman Benson

@Sadeq 50k-60k does seem a bit high, but anything is possible. You can get an idea by going to several manufacturer websites and seeing the rating. It’s hard to assume they will all be alike, but it gives you a good sample, and you will need to indicate as much.

137. akshay

hi sir my question is which dc motor gives max volt in minimum rpm ?
if suppose i have mechanism which convert mechanical energy (rotary motion) in to elecrical energy so which dc motor is gives max volt in mini rpm

• Coleman Benson

@akshay You are referring to a generator. Many generators (wind or water based) still use gearing to speed up the rotation of the motor based on input. This also means a higher torque is required to rotate the gears and motor.

138. John

I am designing a robot that moves and shoots tennis balls at various speeds. I understand all the inputs required to figure out what dc motor specs are needed for the wheels that propel the robot, but how do I figure out the resistance, ie maximum torque, created by the tennis balls being squeezed through the counter rotating wheels that propel the ball forward after it drops down the chute? I know how much the ball gets squeezed because I know the distance between the counter rotating wheels but this is a force that is perpendicular to the wheels not tangential. Any ideas about how to calculate this would be appreciated.

• Coleman Benson

@John Unfortunately that’s well beyond the scope of this article. You might consider creating a new topic on the RobotShop or Letsmakerobots forums.

139. Nick

What should be my motor specifications if my robot has two wheels(connected to two separate motors) and the maximum voltage(power supply) which I can give to the robot is 12V

140. Shweta

Hi sir! Actually my doubt is how to control dc motor rpm or speed? Is there any kind of resistor I need to join for this? Actually I am doing simple lamp waterfall and I require minimum speed for this, because it will take water slowly.

141. Mithun

HI SIR. Which dc motor should I use for my lower exoskeleton system,its 24V, for hips and knee?

• Coleman Benson

@Mithun You really need to do a torque / force balance on your end in order to know the specs of the motor (torque, rpm, weight etc.). A powered exoskeleton project can be quite expensive as they need ultralight puck actuators which provide high torque.

142. RCSN

Hello Mr. Benson, I would like to build a small scale weeder kind of thing which would actually dig surface to remove grass, weed etc., I have the mechanical side built. It weighs about half a kg. I am thinking of buying a DC geared motor the one with yellow rectangle motor. What would be the motor specification for this? Thanks in advance for your rely.

• Coleman Benson

@RCSN We offer a few such motors and the specs are different for each. It’s best to contact us via the RobotShop Forum or support center with the product SKU(s) and we’ll be happy to help. Note that these are small hobby motors with not much torque.

143. AQ

how could i find combined load capacity of 4 dc gear motors with known torque of 2 Nm each????

144. Shahul

Sir, I am building a e vehicle with BLDC 2.2KW motor rated as 48V and 50A. Now I am planning to go with lithium ion. The controller I use has surge protection it says, Is it sufficient if my battery can supply only the rated current? I mean 50A( maximum continous dicharge of battery) ? And can we use lithium polymer for electric vehicles, Is it good to use?

• Coleman Benson

@Shahul Ideally your main battery should be able to supply a lot more current than what will be consumed under normal use. Surge protection will help, but it’s not an ideal solution. LiPo is common for EVs, but be sure to have a complete, rigid enclosure which is well ventilated. Since it sounds like you’re building an actual car (or similar), it’s good to be in touch with the manufacturers of the batteries and the motor controller to get their input. They are often ready to help and give advice.

145. Anusha

Sir, motor speed 2900 And Fan Speed 2450 if Which type of VFD I selected please tell me.And which parameters based I select the VFD.

146. farzeen

sir, i am making a sumo robot of 1 kg for a robotics competition. I just want to know i f i want to push the opponent robot then the dc geared motor of which rpm should i have to use ? And also can u explain the relationship between rpm of the motor and the power drawn by it?

• Coleman Benson

@farzeen There are many factors to sumo robots, of which one is rpm, the other torque, another are the sensors used and then the code. The overall shape will have an impact as well. You would likely use a DC motor, encoder and motor controller. At lower speeds, the motor tends not to be able to provide as much torque as compared to when it’s operating at its rated / max rpm. Some motor manufacturers provide a curve of torque vs. rpm, as well as torque vs current, but unfortunately most do not.

147. David Pents

Hello, my name is David, I’m an artist whom tattoos in leather. I have some questions and I hope that you can and will help me, even though these are not relevant with robots, but I don’t know where else to ask them. I’m tweaking a tattoo machine. Motor width: max 24mm. Lenght approx: 32mm (ex shaft/axle)

Q1: If a machine works 8000 rpm @ 12volts, it would be +/- 4000 rpm @ 6volts. But the needle hits softer with less rpm, I think. If the wattage of the motor was higher, say: 10 watt instead of 3W. would the needle hit harder on 4000 rpm @ 6volts?
Q2: Or should I change the voltage on the motor? Use a 6volts, 9volts or a 18 volts motor? Which would give a harder hit/bigger torque at 4000rpm?
Q3: Which motor would you recommend? Well I hope you can help in my quest and hope to hear from you soon. With kind regards,
David.

• Coleman Benson

@David Pents We’d be happy to help, but since this might involve some back and forth – can you create a new topic on the RobotShop Forum? Thanks. We have truncated your post here.

148. ponraj

Sir..Im going to design a stair climbing robot using rocker bogie mechanism with 6 wheels.Im also going to use 12v dc geared motor with 30rpm for each wheels.
I want to know is it enough to carry a load of 5kg for 6 motors in steps without problem.

• Coleman Benson

@ponraj The motor’s torque as well as the grip of the wheels on the stair, and the dimensions of the rocker-bogie will play the most important roles. RPM and voltage are secondary. For each step, the rear four wheels will push the front two against the stair, adding to the friction. If you really want to know if it will support 5Kg, you have quite a few equations and calculations to go through.

149. Ramu

I have a Old Servo Motor with serial port and feedback connector, can you please help me how to use the motor, I need a high speed motor with good power, can i use this motor.

• Coleman Benson

@Ramu Create a new post on the RobotShop Forum with as many details and images as you can. We’d need to know the brand, model, connector etc.

150. Vignesh R

I’m trying to design a linear motion actuator which will have 10 kg pulley attached to it…this pulley needs to be moving front and back at variable speeds… I’m trying to use 12v DC motor..how to select a proper motor with given requirements…I’m novice in this..this is my first project and ur help would be much useful

• Coleman Benson

@Vignesh R Would need to see a sketch or drawing explaining the motion. Can you create a new post on the RobotShop Forum and provide as many details as possible?

151. Kathy Bthomas

Very Informative post. Thanks for sharing.

152. Dashiell

I have a DC motor from an elegoo set, I don’t know the nominal voltage however the entire set ran off of 2 3.7v 2200mAh batteries, because this is just one motor could I get away with using only one battery?

• Eric Nantel

@Dashiell, There is no good answer to this question since we do not have enough information from your original setup. Are those batteries in Series or Parallel ? If you have two cells in parallel you will get 3.7V but in series it will be 7.4V.

153. john pierced

hi i am trying to figure out what size of dc motor most likely 24v that would produce atleast 18050 #ft torque that could be coupled to a 18 speed gear reducer to be able to move 30 tons

• Coleman Benson

@john pierced If you really want DC, you’ll need to know the diameter of the winch drum to use T=F*R. 30 tons = 60k pounds, so if you choose a 4″ diameter drum (1/3 foot), the motor would need 60k*1/3 = 20k pound feet of torque. We do not offer anything in that range – you might want to look at existing winch systems for trucks and adapt it to your needs.