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Topic: Christmas LED String (Read 996 times) previous topic - next topic

mrlj-

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. :)

SurferTim

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

mrlj-


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..

SurferTim

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.


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