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2-16 channel servo controllers with 12 servos each on Beagle
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2-16 channel servo controllers with 12 servos each on Beagle

by flynnboyo on Sat May 17, 2014 1:22 am

As the subjects says, I have 2 servo controllers with 12 6volt servos hooked up to each of them. I've addressed them as 40 and 41. I installed 2200uF 6.3volt caps on the controller boards. I've got a 6volt 2.5amp power source that I split into the controller terminals. I've got the controllers hooked up to my i2c pins on the BBB(19&20) and when I run "i2cdetect -r 1" I see the controller addresses recognized: 40: 40 41 -- -- -- -- -- -- -- -- -- -- -- -- -- --

My problem is that when I apply power all of my servos start jerking one direction in unison a little bit about every 3 seconds.

I have run the Servo_Example.py file to test it which doesn't seem to have any effect on what's happening. I have tried it as is and with a PWM object instanciation for each controller pwm1 = PWM(0x40, debug=True) & pwm2 = PWM(0x41, debug=True). I really don't think this part matters as I doubt it is even getting this far..

I have tried connecting a ground from the power supply to various grounds on the controllers and BBB which also has no effect.

Is there something wrong with my initial set up?

Thanks

flynnboyo
 
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Joined: Sat May 10, 2014 11:01 am

Re: 2-16 channel servo controllers with 12 servos each on Be

by adafruit_support_bill on Sat May 17, 2014 6:39 am

So you have 24 servos and a 2.5 amp supply? That's a little over 100mA per servo. Most servos need more than that. Unless they are all micro servos, I'd expect they are overloading your power supply. The 3 second cycling is probably your power supply going in and out of thermal shutdown.

Try with just a couple of servos first. Either check the specs for your servos or measure the actual current draw.

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Re: 2-16 channel servo controllers with 12 servos each on Be

by flynnboyo on Sat May 17, 2014 6:47 pm

Thank you for the response, Bill. I'm sorry I should have mentioned that the mini-servos(mg90s) are rated at 100 ma each. I actually did the math when I went with 2.5 amps. Also, I did try running 12 instead of 24 with the power supply and it behaved exactly the same way. I have run 12 with this power supply successfully straight off of a RPi(with servoblaster and the P5 pins installed). I purchased these controllers so I could add the 4 additional legs to my octoped. I had been testing with 4 legs. I had similar problems with the first set up which adding a ground from the power supply to the board solved before but it doesn't seem to be making a difference this time around. Thanks for your help.

flynnboyo
 
Posts: 13
Joined: Sat May 10, 2014 11:01 am

Re: 2-16 channel servo controllers with 12 servos each on Be

by flynnboyo on Sat May 17, 2014 7:00 pm

One more thing. I have the controller boards hooked up to 3.3v. I see that you told someone to go with 5v in this thread viewtopic.php?f=22&t=28951

flynnboyo
 
Posts: 13
Joined: Sat May 10, 2014 11:01 am

Re: 2-16 channel servo controllers with 12 servos each on Be

by adafruit_support_bill on Sun May 18, 2014 6:36 am

The PCA9685 can run on 3.3v, so that is not likely the problem. Post a photo showing your soldering and connections and we'ss see if we can spot anything suspicious.

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Re: 2-16 channel servo controllers with 12 servos each on Be

by flynnboyo on Sun May 18, 2014 2:41 pm

Hey Bill,
In the act of breaking this beastie open to take some pics I must have tightened something that was lose up. He just about jumped off of the table at me when I ran the servo example looped through all of his servos. This is a great company and thank you for your time. Here's the project thread if you are curious https://twitter.com/Arachnoid1x

Thanks again.

flynnboyo
 
Posts: 13
Joined: Sat May 10, 2014 11:01 am

Re: 2-16 channel servo controllers with 12 servos each on Be

by adafruit_support_bill on Sun May 18, 2014 4:18 pm

Nice looking project! Glat it's all working for you now.

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Please be positive and constructive with your questions and comments.