Christmas LED String

Other Hardware LEDs and Multiplexing
1

Hello,

I have a cheapy solar powered christmas LED string that has packed up so I thought I'd try and do something with the Arduino.

I've cut the string apart and powered the LEDs up but it appears they have a common positive instead of common ground.
Is it possible to still use these in a project without getting ridiculously complicated/cutting them apart?

Thanks for your help. :slight_smile:

2

For me, a common anode setup is easier. The cathodes can be controlled by a single NPN transistor.

3

SurferTim:
For me, a common anode setup is easier. The cathodes can be controlled by a single NPN transistor.

Wow - that made absolutely no sense to me! I'm a complete beginner with this..

4

It doesn't matter which end of the LED you control the current at, as long as it can be turned on and off.

V+ -> switch - > resistor -> anode LED cathode - > GND (common cathode)
or
V+ -> anode LED cathode -> resistor -> switch -> GND (common anode)

The second way requires only a 2N2222 transistor to replace the switch.