- Wed Jul 11, 2012 12:47 pm
#147277
but I'd be supplying the LEDs with 5v, not 12v? I intend on using the 12v to switch the transistor on? will that not fly?
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hassmaschine wrote:but I'd be supplying the LEDs with 5v, not 12v?Ahhh, now I understand. At one point I thought you weren't sure the cluster had enough 5V "umpf" left to run the LEDs and so were going to run them off 12V.
I intend on using the 12v to switch the transistor on? will that not fly?It should fly just fine.
hassmaschine wrote:okay, I've got the circuit built and it works! yay!Hmmmm. If you've disconnected 5V from the system and still get the LEDs to come on, it means there's another source of current for the LEDs someplace in the cluster, no doubt some indirect path through some "high" resistance. The value of R2 shouldn't make any difference. If you increase it enough to stop any light output, it won't work when the 5V to the LEDs is present. There's no way the 12V is going through the transistor to turn on the LEDs. Something is not quite the way we think it is. Is it possible the cluster has another "driver circuit", in parallel with the transistor you've added, and that's somehow suppling power to the LEDs ??
question - it appears I get some current leakage from the 12v source. If I disconnect 5v and switch the transistor on, it still powers the backlights (albiet dimly). That means I should increase R2, correct?