After a long night I managed to frickle together the hardware and program it to walk. It used to work quite fine, but ever more often it would not work when running on battery: when attached to a 9-Volt-Block most of the time now the Servos do not do what they are programmed to but jump to random uninetended positions. However I did have the same problems once or twice when powered through the USB-Port if I remember correctly...
The battery power supply (9 V Block) is attached to the Arduino Board only (Jumper/Barrel Jack), which powers the Servos and the Board over the same 5V-Output. And I think somewhere here lies the problem? The battery still has around 8 Volts, which should be sufficient, right?
I read a lot about where the problem could lie, but am still quite confused, so maybe someone here could help me?
Am I right in linking the problems to the power setup? Or could there be other explanations (is there a minimum delay between new positions?)?
Can i solve it with one battery only (that directly connects to the PCA9685/Servos)?
As the PCA9685 and the Servos can only handle max. 6V i guess I need something less powerful than the 9V-Block - What should I use? I am currently thinking about 2*18650-Batteries, but they would add up to over 6 V as well?
As they are pretty small they don't seem to use a lot of mA, according to the seller only 100 mA each... Also with the USB support it works quite stable, so I guess they should indeed use less than 450 mA in total.
Nevertheless thanks to your link I conclude that with the dropping voltage of the Battery Block the current available via the power jack & pin dropped to less than what they need. And not enough power leads to random jumps?
Then a 5-6 V battery supply could do the trick, I guess! But - back to my first questions: what should I use as a supply? The only solution seems to be 4AA? Or would 218650 be okay for the Servos?
4 x AA NiMH rechargeable batteries (e.g. Eneloops) make a good supply for small servos. Most servos are not specified for the much higher voltage of 2 x 18650s.
Note that when you use a 9V battery you are relying on the small onboard regulator to supply the 5V pin. Powering via USB bypasses this which is why you may get away with it.
I'd use a multi-meter to get a reading of the current being drawn, whiles the system is in operation. I'd get an idea of type of battery supply vs expected run time.
The SG-90 servos that OP linked to have a stall current of 650mA at 5volt.
The supply must be able to deliver 4*0.65= 2.6Amp peaks for the servos alone.
Leo..
Great, thanks for all the input - especially the fact about bypassing the regulator and the Amp-Infos! I'll get 4*AA rechargable batteries then.
One last question: is there a limit of current I should keep in mind? I read somewhere that batteries should not be drained in less than an hour; but is there also a peak-maximum for such batteries?
Please read the first post in any forum entitled how to use this forum. http://forum.arduino.cc/index.php/topic,148850.0.html .
Then look down to item #7 about how to post your code.
It will be formatted in a scrolling window that makes it easier to read.
Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?
