I've been testing the new leg with one power supply for the servos and one for the electronics and all is working well. I expect that all would be working well if I were using a single power supply for both, as long as I was using the new one I soldered up and not the old one...
I decided that since I would be using a 5v power supply for most of the bits of this project that I'd grab and old mains transformer and wire up a 5v regulator and run from the mains rather than batteries. Since this took up a chunk of space on my breadboard I decided to make it a little more permanent on some strip board.
I pretty much followed the Sparkfun power supply tutorial with a little artistic license for the 'front panel' and so had a PTC resettable fuse in there to limit the current in case of short circuits, etc. Anyway, it was the PTC that was causing the problem with the servos. It was doing what it should but the servos were trying to pull more current than it would allow and so it was cutting the power (and resetting the servo controller).
Anyway, once I realised what I thought was going on I slapped the multimeter into the circuit and watched the PTC cut out as the servos pulled more current than it allowed.
The new power supply is pretty much the same as the old one without the PTC (I'll rely on the protection in the voltage regulators for this one) and with a 3.3v output as well as a 5v output.
The servos run fine now and the current draw is within the spec of the regulator. One more small piece of knowledge acquired...
hi,
very interesting blog! i have a question about using a servo. right now, i have a mystery micro servo 9g, i cannot find the specification for how much current it draw under load, but i measured around 600ma. my supply is 750ma and i am using the supply for 2 avr, 1 op-amp, 1 audio amplifier and the servo. i get noise in the sound when the servo is moving... of course using a separate supply is fixing the problem, but i would to use only 1 supply.
any recommandation? i am using 3 voltage regulator (3.3v (avr), 5v (op-amp, avr), 10v (audio amplifier)).
thx!
cheers,
pat
Hmm, that's probably a bit beyond my level of knowledge unfortunately. As a wild guess I'd try increasing the size of the caps you have around your regulators as that may smooth things out a bit. You'll probably get a proper answer over at AVRFreaks or at Chiphacker.com.