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Diodes to avoid servo jitters while I am using Adafruit 16ch
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Diodes to avoid servo jitters while I am using Adafruit 16ch

by aldoz on Sat Aug 10, 2019 6:45 am

Hi guys!
I am in full developement of a quadruped robot and I am really close to some good results.
https://www.hackster.io/aldoz/jqr-quadruped-autonomous-robot-update-25-may-2019-7475a5

I am using your 16ch servo driver linked to an Arduino MEGA2560:
https://learn.adafruit.com/16-channel-pwm-servo-driver/overview

Ok I am using 12 servo:
https://www.conrad.it/p/bluebird-standard-servo-bms-620mg-servo-analogico-materiale-trasmissione-metallo-sistema-innesto-jr-275462

here my battery to power servos (using stepdowns and a lot of complicated wiring..)
https://www.conrad.it/p/gens-ace-batteria-ricaricabile-lipo-111-v-2700-mah-numero-di-celle-3-25-c-softcase-xt60-1644335

without getting into the problem too much, I am having a lot of problems with the jitter effect of the servomotors. I have tried many solutions but it is a difficult problem to solve.
Please, look at this link, there seems to be a possible VERY EASY solution to this problem:
http://www.gioblu.com/index.php?option=com_content&view=article&id=167:eliminare-interferenze-date-dai-servomotori&catid=43:azionamenti&Itemid=35

So, you can see that in that example the servo is attached directly to Arduino so my question is:
Can I use dioedes, like in this example, while I am using your Adafruit 16ch board?
and if YES, how?

Thank you all in advance.
aldoz
 
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Re: Diodes to avoid servo jitters while I am using Adafruit

by adafruit_support_bill on Sat Aug 10, 2019 7:22 am

There are many sources of jitter and interference in complex electromechanical systems like robots. The diode addresses one of the most common. You can implement that remedy easily by wiring the dode between the + and - terminals on the external power connector on the driver board.

Adding a large electrolytic capacitor in the location marked "C2" will also help filter voltage fluctuations caused by servo current demands.

adafruit_support_bill
 
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Re: Diodes to avoid servo jitters while I am using Adafruit

by aldoz on Sat Aug 10, 2019 11:02 am

In first thank you Bill for your fast help.

You can implement that remedy easily by wiring the dode between the + and - terminals on the external power connector on the driver board.

the difference between your solution and the one I proposed is that in your solution you don't use the diode for each of the servos (so I would have had to use 12 diodes) but instead use a single diode at the input of the pins of the servo power supply. it is Correct?
(I am already using a 3300 uF capacitor in the "C2" location but jitter continues)

So please take a look at the image, I need to be sure not to do damage :) :

And, considering my 12 servos, can you recommend the right diode?
Attachments
adafruit_diode.jpg
adafruit_diode.jpg (71.91 KiB) Viewed 108 times
aldoz
 
Posts: 31
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Re: Diodes to avoid servo jitters while I am using Adafruit

by adafruit_support_bill on Sat Aug 10, 2019 11:13 am

The diagram is correct. You would want a diode that is rated for at least as much current as your servos will draw. For example, if each servo draws 500mA, you would want a diode rated for 12 x 500mA = 6A or more.

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Re: Diodes to avoid servo jitters while I am using Adafruit

by aldoz on Sat Aug 10, 2019 11:58 am

adafruit_support_bill wrote:The diagram is correct. You would want a diode that is rated for at least as much current as your servos will draw. For example, if each servo draws 500mA, you would want a diode rated for 12 x 500mA = 6A or more.


Bill really thank you for support!
aldoz
 
Posts: 31
Joined: Mon May 12, 2014 7:24 pm

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