LED's light up with battery but when connected to the arduino they don't - Help!

Other Hardware LEDs and Multiplexing
1

Hello,
I have made a sort of light box using LED's. I have 4 sets of 12 LED's (in series/parallel circuits) with resistors and they all work fine with a 9V battery. I can attach all 4 sets to the battery and they all light up. But as soon as I attach them to the circuit board I made that sits on top of the arduino (using the same battery) they won't light. I tried it with the basic examples blink and fade but nothing...I have used the circuit board and arduino to light up other LED's and Motors so I know it works.

I don't know if I have explained this very well, but I'm new at this and still learning...if anyone could suggest what the problem might be it would be greatly appreciated! Thank you!

Is it possible that the cable I am using isn't compatible with the arduino?? This was the only thing that occurred to me...

2

Hi,

The Arduino outputs are 5V, not 9V, and the maximum current is 40mA (and the output voltage will be even lower at 40mA). So your leds will not light, and its possible you have already damaged the Arduino output.

You need a transistor to handle the 9V supply and all the current those leds need. Bc337 should be ok. Use a 1K resistor on the base.

Paul

3

RosyArgi:
Hello,
I have made a sort of light box using LED's. I have 4 sets of 12 LED's (in series/parallel circuits) with resistors and they all work fine with a 9V battery. I can attach all 4 sets to the battery and they all light up. But as soon as I attach them to the circuit board I made that sits on top of the arduino (using the same battery) they won't light. I tried it with the basic examples blink and fade but nothing...I have used the circuit board and arduino to light up other LED's and Motors so I know it works.

I don't know if I have explained this very well, but I'm new at this and still learning...if anyone could suggest what the problem might be it would be greatly appreciated! Thank you!

Is it possible that the cable I am using isn't compatible with the arduino?? This was the only thing that occurred to me...

You stated, "Circuit board I made that sits on top of the arduino (using the same battery) they won't light."
Obviously, something is different.
Therefore, you should post BOTH schematics.