b4039 b

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5 years, 10 months ago.

Powering mbed externally with 5v supply

I'm using a 5v power supply (http://www.hobbyandyou.com/adraxx-33v-and-5v-power-supply-module-for-mb102-bread-board) to power an mbed externally. Negative is connected to Vin, and Positive to GND. I've written a simple program which lights up all 4 LEDs on the mbed board. When the 5v supply is turned on, the LEDs do light up, but to a lower brightness than when connected via USB, and a faint flicker.

Can anyone explain why this is? I measured the voltage coming out of the 5v supply, and the figure tends to move between 4.9-5.1, which I believe is within the mbed's range.

At times, the flicker is more prominent with the LEDs completely switching off and on.

posted by b4039 b 18 Jun 2018

1 Answer

Peter Nguyen
5 years, 10 months ago.

Hi EB,

Please check to see your Power connection is correct. Vin should be connect to the positive terminal and GND should be connect to the negative terminal. If you switched them, then you are not powering the board correctly.

Please let me know if you have any questions!

- Peter, team Mbed

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Vin for the LPC1768 should be between 4.5-9V Make sure its no too low on the actual Vin pin due to bad wiring contacts. And yes, Positive to Vin, Negative to GND.

posted by Wim Huiskamp 18 Jun 2018