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Hook-up to external power help

Topic last updated 15 Sep 2011, by Martin Smith. 3 replies
Jesus Rocha
15 Sep 2011

I want to hookup mbed to an external power supply which I picked up at the store. The power is 5V at 2AMP, now the specification for the board says:

Vin - External Power supply to the board 4.5v-9v, 100mA + external circuits powered through the Microcontroller

The question is can I hookup the power supply directly and assume the microcontroller will only consume 100mA? or do I need to reduce the amps, and what is the maximum amp's that should be connected alongside the 5V's?

Thanks!

Gert van der Knokke
15 Sep 2011

2 Amp is the maximum current that powersupply can deliver at the given voltage (5 Volt) So if your mbed is drawing 100 mA then it has 1900 mA left for other devices you connect.

Jesus Rocha
15 Sep 2011

Thanks, wanted to be sure I'm not compromising the mbed. I was asked to get a .8mA low dropout voltage regulator by the professor, does the mbed require it? or can it be required for the other IC's on the board?

Martin Smith
15 Sep 2011

I guess your prof. wants to ensure the mbed has a clean supply? You shouldn't really need it, just plug the 5V straight into the mbed - it will be fine. If you like you can strap some caps across the power rails just to smooth out the supply a little, maybe a 47uF and a 100nF?