hello, I bought a 5v usb wall charger for my mbed and I thought that I could plug the USB into that and it doesn't seem to be working. The lights on the ethernet jack turn on but no LEDs on the mbed... What do I need to power the mbed not from a computer? This is what I bought http://www.sparkfun.com/products/10214 Thanks for any help!

I use a 5v regulated power supply but I connect it to VIN PIN2 and GRD PIN1, not the USB connector.

maybe this specific wall charger is supplying too much current and the mbed's current limiter is kicking in?

@Kevin LeCroy could you send me a link of the one you bought? Thanks!

Eh? That makes no sense at all, if you think about it.

I'm not sure why your power supply is not working. I'm pretty sure that 500ma is enough current.

I use an old computer power supply with the 12v output connected to an LM7805 5V voltage regulator like this: http://www.tkk.fi/Misc/Electronics/circuits/psu_5v.html

You could try this:

Cut the end off of a spare USB cable, connect it to your power supply and then connect the +5V (red wire) to PIN2 VIN and GRD (Black Wire) to PIN1 GRD.

USB Cable: Red wire = +5V, Black Wire = GRD

A power supply that is capable of supply 500ma is only CAPABLE of supplying that much current. It is the load that you put on the power supply that will determine how much current is drawn from the power supply.

OP may confuse the term "current" with "voltage".

Actually this should work - I'm using just this setup (using a wall charger from my old Motorola phone). But it might be that the charger supply is somehow waiting for a proper response from the actual charger before it delivers enough cuurent (kind of the reverse thing what the iPod and the like are doing).

Ok thanks for all the help. I actually got my motorola charger...it's got a little more juice...it's 5.1v and 850mA is this bad for the mbed to use this? when i use the 5v 500ma it doesn't work. i'm using an ethernetjack, lcd display, a camera and a sensor. i guess to power all that i need a little extra?

Powering the mbed Pin2 VIN with a 5.1v source capable of 850mA is fine. The Pin2 VIN is good for 4.5v-9.0v. Again, the mA rating on a power supply is the maximum current that the power supply can output. The actual current drawn is a function of the load that the circuit the power supply is connected to draws.

Just make sure that your power supply is regulated in that it stays 5.1v no matter what load you put on it (withing the specified voltage range that is). Don't use a "wall wart" or similar power supply without a regulator otherwise when there is little load the voltage could be much be higher that 5v.

Use a self-powered usb hub with its own wall wart to supply your circuit without loading your pc's supply. Safe, cheap and idiot-proof.