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Help with Unresponsive servos

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Veteran ( offline )
Posts: 149
Posted: 2012-01-24 12:55 
Hello everyone,

Im almost done with a robot i was making from scratch ( a quadruped ), got all the parts cut and the electronics ordered !. Yesterday, i was making a program that simply centers all the servos. Im using Bot Board 2 and basic atom pro 28 powered by 6.0 Volt Ni-MH 2800mAh Battery Pack, things are all set and ready to go!.

I turned on the switch, the program starts, but the servos never budge.They make a buzzing sound as if they're stuck but i can freely move them by hand as if they were unpowered. I thought at 1st the body was too heavy on them so i lifted it up but still nothing so far,i also used 9v battery but still. Here is the code im using :


Code:
pause 1000

main

hservo[0\127,1\127,2\127,3\127,4\127,5\127,6\127,7\127,8\127,9\127,10\127,11\127]

goto main


The servos use pins from p0 to p11 while ps2 receiver has the pins p12 to p15 , the servos are Hitec 255bb mighty mini servos, 16 of them ( 12 working and 4 of them ill connect to 1 pin later as they move together in the same time ).

Thanks for help and the wonderful forums :)


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Guru ( offline )
Posts: 9258
Posted: 2012-01-24 12:58 
Can you post an image of your wiring?

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Veteran ( offline )
Posts: 149
Posted: 2012-01-24 13:20 
sorry that the wires look kinda messy since im not focusing on the looks now, here it is:

http://www.truploader.com/uploads/1_24_ ... .10.53.jpg


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Guru ( offline )
Posts: 9258
Posted: 2012-01-24 13:51 
Yeah that helps... Two things.

Your battery wiring harness has wires frayed at the connector. Please go back and carefully make sure there are no wires sticking out. The way it is now, it could short out and the battery would heat up!

The jumpers above the IO pins set the voltage the servos receive. They can be set for 5vdc or the raw servo voltage. When you're powering servos you need to use VS as the 5vdc regulator on board will not be able to supply the required current. I hope the regulator is not damaged already.

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I've always tried to do my best...


Veteran ( offline )
Posts: 149
Posted: 2012-01-24 14:24 
Thanks for your reply, im done fixing the wire harness and changed the jumpers above the IO pins to vs. Fortunatly the regulator is fine but still the servos arent moving. I removed the vs=vl connector and add 9v to VL and the battery pack to servos only (VS), and the results were better, but still having a problem, 2 legs seem to operate almost at full power while the other two are still dead. im checking my wire connections at the moment to see if something is wrong.

Waiting for your response.

Edit: the buzzing sound can still be heared even though the servo power is off, i think its the speaker.


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Guru ( offline )
Posts: 9258
Posted: 2012-01-24 14:37 
Make sure you moved all jumpers for the banks that have servos connected.

Is the 6vdc battery fully charged?

There is a buzzing sound coming from where? Maybe it's time for a video?

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I've always tried to do my best...


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Guru ( offline )
Posts: 9258
Posted: 2012-01-24 14:47 
Is this a beeping sound? What program are you running?

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I've always tried to do my best...


Veteran ( offline )
Posts: 149
Posted: 2012-01-24 14:48 
All jumpers are connected to vs, the battety 1st use was today and the buzzing sound was coming from the speaker, i simply removed its jumper connector, now its gone :). the unpowered servo problem remains.

Edit: After removing the speaker, some servos that weren't working are working now, seems like a current problem


Robot Dude wrote:
Is this a beeping sound? What program are you running?

pin 9 is the speaker pin, and the program sends pulses to the servo at pin 9 so i think it was sending pulses to the speaker. it would be beeping if it wasnt pulses i guess, im still using the same program.


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Guru ( offline )
Posts: 9258
Posted: 2012-01-24 15:09 
Ok, yes the speaker is on pin 9 and it is clicking with the servo pulses.

There should be no way for the speaker enable jumper to effect the servo pulses. It's not connecting a speaker, but connecting a high impedance input to a low impedance output IO pin.

Do you have the legs supporting the weight of the robot, or is the bot suspended off the ground? Could we get an image of the bot to look for hardware problems? Are you connecting the servos directly, or are you using servo extenders?

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Jim Frye, the Robot Guy
http://www.lynxmotion.com
I've always tried to do my best...


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Guru ( offline )
Posts: 9258
Posted: 2012-01-24 15:10 
Also do you have a volt ohm meter? Can you check the voltage from the 5vdc regulator to ensure it's providing the full 5vdc?

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Jim Frye, the Robot Guy
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I've always tried to do my best...


Veteran ( offline )
Posts: 149
Posted: 2012-01-24 15:12 
i have one, checking now

Edit: yea, its delivering 5vdc


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Guru ( offline )
Posts: 9258
Posted: 2012-01-24 16:06 
When you edit I do not know and it's slowing things down...

You neglected to address these...

Do you have the legs supporting the weight of the robot, or is the bot suspended off the ground? Could we get an image of the bot to look for hardware problems? Are you connecting the servos directly, or are you using servo extenders?

_________________
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I've always tried to do my best...


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Expert ( offline )
Posts: 548
Posted: 2012-01-24 16:30 
Sorry for just turning up out of nowhere but I might have a suggestion (although I'm not sure if it'll work). I saw the code:

Code:
pause 1000

main

hservo[0\127,1\127,2\127,3\127,4\127,5\127,6\127,7\127,8\127,9\127,10\127,11\127]

goto main


And if I remember correctly, the hservo command in the Basic Micro Studio Manual uses the following:

Code:
 main

hservo [p0\0\500, p1\0\500]

goto main


Would it be necessary to have the servo angle (i.e. the bold part of this - p0\0\500) for the code to work? If so, then that might explain why the servo horns can be moved freely.

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Guru ( offline )
Posts: 9258
Posted: 2012-01-24 16:37 
The format is pin, position, speed. So if the speed is not there it will move as fast as possible. I don't think that's it, but there is something missing... enablehservo might help... :oops:

Code:
enablehservo
   hservo [0\0\0]
start:
goto start

_________________
Jim Frye, the Robot Guy
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I've always tried to do my best...


User avatar
Expert ( offline )
Posts: 548
Posted: 2012-01-24 16:42 
I'm pretty sure it works without the ENABLEHSERVO command because I made my robot walk without having it :oops: - I just set up the values with the hservo command and off it went.

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