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Author Topic: 12v common cathode LED strip help  (Read 728 times)
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I am trying to control a strip of leds that run at 12v a share a ground.

At my use I have 3 TIP42 PNP Transistors. and two Darlington Driver 8-Channel ULN2803 DIP, as far as transistors go.

I thought I could get away with just using the pnp's to work the leds but it's not working. Can anyone recommend a schametic that will work? Does the arduino have to have the same ground as the LED or can I power the leds from a 12v source and the arduino from usb or some other power source?
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you can use separate power supplies, but the GNDs do need to be shared. on the TIP42:

+12v -> E pin on TIP42
Arduino pin -> 270ohm ->base pin
C pin on TIP42 -> LOAD(the +12v pin on the LED strip) ->GND
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Thank you for your input. Although it didn't work it did help me to a solution that does. I added some npn transistors infront of them and now it works!
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you got me puzzled, what did you do with these NPNs?
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