Hi guys!
anyone knows what the third wire in a dc motor is for? I have two dc motors with 3 wires (blue, yellow and black), the first two are the common ones but don't know why there is a third one. I have unscrewed the cap of the motor and this wire is connected to the shield / armour of the motor.
Perhaps I should connect this wire to ground to minimize EMI... Any ideas? Thanks
Do you have a picture or a
Do you have a picture or a specification for the motor?
You could be looking at a DC stepper motor. Stepper motors require a sequence of pulses across each wire in order to move.
Here’s a good site on understanding the various types of stepper motors: Jones on Steppers
brushless ?
I think brushless motors have three wires…
Both motors are part of a RC
Both motors are part of a RC car and those are DC. I can control the speed of the motors using a brushed ESC Turnigy 20A, so I’m sure it’s not a 3-phase motor.
Also the yellow and blue wires (+ and -) of the motor are much thicker than the black one.
I’ve got the same thing here
I’ve got the same thing here om my tank chassis. black wire not connected now, could be against noise from the motors I think…
when adding power to the 2 other wires the motor just works.
I also see sometimes motors with 2 caps between the 2 wires and the housing.
edit: as shown here: http://www.pololu.com/docs/0J15/9
If this is what alexnomad
If this is what alexnomad has as well, I agree that the smaller black wire is probably a ‘case ground’. The motor should work fine without it. Connecting your motor’s case electrically to the frame of your robot may help reduce some electrical noise.
Do not connect the case ground (black wire) directly to your power ground or signal ground on your controller.
The method or noise reduction shown at the Pololu link Dannyv provided is more common for our robotics applications. Wherever you got your motors from, they may have been intended for an application where the motor case would be grounded to the frame of whatever they were installed in.
pololu link
Thanks for the link dannyv! You've got the picture here. It has all the capacitors mentioned (3) one between poles and two more between each pole and the motor case.
I believed that this black wire was related to some noise supression but the link showed the theory.
It won't be impossible to make the connection ignoblegnome said as the frame of the car is made of plastic (but I will remember for future robots) but I will twist the blue and yellow wires to minimize interference.
