Troubleshooting Help! mBed powered off if wire touches vOut

19 Feb 2012

Hello mBed community, I just wired quite an intricate circuit with tons of wires, color coded, all that fancy stuff, and I plan to power everything from the mBed 3.3V out. It's connected to my laptop, so power should not be an issue. If I connect the power supply wire of my circuit (nothing on it yet) the mBed shuts off. I tried to find a short between Power & GND but can't seem to find one. HOw should I go about trouble shooting this? I have 6 ICs and a gaming controller with about 30 wires going into this thing. Please let me know something ASAP, big project due soon :X !

Thanks!

20 Feb 2012

It turns off if you pull too much current on the USB port - USB can only provide 500MA - after mbed only about 200MA is left for everything else.

You will probably need an external supply - connect gnds but not the outputs.

19 Feb 2012

Also if the electronics you are using has an inductive load,

Such as a relay, then the surge current can quite easily be ten times What you might expect. I vaguely remember a game controller With shaking motors.

Ceri.

19 Feb 2012

That'll explain it. Thanks! I guess I'll have to pull out an old cell phone charger. I just want to keep my circuit with minimum power cables -_-.