Servo power circuit

[zaobz]

Hi,
I'm building a system that is using 21 of GWS MICRO 2BBMG servos. I seem to be having problem when I connect all 21 servos, because it seems like it creates alot of spikes on the powerline. I'm wondering what kind of circuit is used to power servos?
Right now Im just connecting them straight to a LM338 (5V, 5A) I know I probably should have capacitors across each servo, but I'm wondering if anyone has any suggestion on the values of the caps?

TIA!

[Trevor_G]

I don't know the GWS servo you mention but that type of servo generally stalls @ 1A. Total Max load 21A:eek: . Under twitching conditions maybe 10A. I think you are pushing a single LM338 a bit hard.

The main thing I would look at is the wiring. You need to ensure that it can support the current without a large voltage drop. In particular the Ovolt cabling needs attention to ensure that the i/p signal is not corrupted. The best technique is to "star" the power lines together and ensure the Rx (or whatever you are driving the servos with) also has its OV line connected to the star point.

I don't know what you are powering the LM338 with but at 10A you will need the regulator to get rid of 10W for every volt over 5V (min 30W). Things will get very hot.

As for capacitors I would probably put 1000uF across the Star point to handle spikes but rate the supply to handle surges.

I would also put the Rx(or whatever) on an independant regulator/supply.