I have four small servos, my ESC and my receiver connected to the APM. When I power it with the USB port the servos twitch a lot and I cannot setup the APM using the CLI. It's fine with the servos disconnected. Is this normal?
Peter
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Darren, you should start to look alternative solutions like using battery to power up your +5 rails. All new APM's won't even provide +5v to R/C rail anymore, this is to prevent brownouts.
Like Davey said on earlier message, different USB's provides different amount of mAh's but still it's not wise to use servos from USB.
My MacBook Pro can run easily 2 x 5g servos but my Dell laptop cannot.
In the begining, I used this cable below to power the APM (to solve the brownout issue before the fix came out) when using servos on the bench.
However, since then, I run the APM on seperate power to the Vin port on the APM board. (removed the solder blob)
The cable below came with a verizonwireless mobile broadband card, that added power to boost the usb modem.
So I dont know where to get one, I assume its not the best solution, but it worked ;)
It sounds like your servos are pulling to much current and the voltage is dipping. USBs are not a good way to power a lot of servos (I think it says somewhere in the Wiki two max).
USB ports also vary massively depending on manufacturer. Some can supply much more current than others.
Regards
D