Led matrix with external power

Other Hardware LEDs and Multiplexing
1

Hello gang

I have a Arduino Mega with a led matrix 8x32, I try to run a example from Adafruit, MatrixTest, it display a Howdy on the matrix.

It work great when I use the 5v power from the Arduino, but when I use the power supply (5v 10a) third of the matrix open (very bright) with some animation in it. I try 2 different power supply and 2 different matrix, same result.

I check the voltage on the power supply and it really 5v, same as the power from Arduino.

What can be wrong ???, I'm new with Arduino, BUT It is hard to believe I cannot make this work with a external power supply.

Thanks for the help

Bill

2

Do you have common ground between the Arduino and the external power supply?

3

Hello

It's a 3 wires led matrix (8x32, I have two), I test them together and separately, same issue (maybe both are bad)

I connect the DOUT to pin 6, and the 5v and neg to the power supply or the Arduino (5v out, neg), no common ground, the Arduino is powered by the USB from a iMac.

Again it is working great without the power supply, this is why I don't understand.. So weird

I think I will order another Arduino mega, it's the only thing I didn't test

Also the two power supply I test with are totally different brand and model, both are 5v (I verified them) the Amp is different.

A big thanks

4

What can be wrong

You could be putting the power into the power jack socket, that requires a minimum of 6.5V .

no common ground,

It can not work without a common ground. Connect the power supply ground ( negitave ) to the Arduino Gnd pin.

5

Wow, thanks Mike

It's fixed my issue, the common ground thing.

Finally, I can go further in my new project, it cost me a second power supply, next time I will post here before.

Again thanks

6

PaulRB:
Do you have common ground between the Arduino and the external power supply?

lebill:
Wow, thanks Mike

It's fixed my issue, the common ground thing.

?