Arduino not working with 5v pins supply

I am using the Arduino Uno with some LED strip lights. I have a external power supply that feeds the lights and the Uno the problem is, when I use external supply and use the 5v and Gnd pin on the board my board does not operate the lights. when I use the USB connection then the lights work fine.

I have used the same connection configuration the only difference is that I am using the USB to power the UNO and it works when I use the external Power supply nothing....

could some one please explane why the 5v pins supply does not work..


Draw a picture of how it is all connected. Photograph it and post it.

Without knowing all the connections, it is hard to say.


1) How long is your LED strip light (1m-5m)? 2) Specifications of external power supply, the operational voltage is 7-12V. 3) If you re using UNO board, the current output on 5V pin can be 500mA (with USB) or 500mA-1A (with external power supply).

It looks like that you USB cable provides more current than your power supply does.

You cannot use 5v on the VIN pin as it goes through the voltage regulator. P. S. You should consider not using yhe arduino's 5v pin to power the led strip. Use a power transistor instead.

The OP did not refer to the Vin, but did say 5v pin.


"could some one please explane why the 5v pins supply does not work."

With a volt meter on the 5v pin, what is the reading?

thanks guy for all your help.. it seems that the wires to the 5v and GRN pin on the Arduino were on put in properly when the resin filled it..

for I went an brough an other one and it seem to work with the pins..

the external supply is 5V 60A.. this is supplying power to both the LED strip lights and the Arduino Uno seperatly the LED length has no effect on the system for I have tried it with 1m up to 30m. and it works..

thanks again for all your help. it seem.

Don't short out that supply as it will destroy anything going through the board!