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Topic: Why i am killing my tip120 ? (Read 1 time) previous topic - next topic

cjdelphi

What, where's the voltage in (5v supply directly from USB) pin? i see 2 2v pins, surely not 1 is Vin?  :smiley-eek-blue:

cjdelphi

different LED's require different voltages, Red being the brightest with the least (something to do with the band gap, wavelengths and things I never understood)

White for example will light dimly from a 3v cell coin, but a Red will shine really brightly... so if you used a white led, combine it with a voltage drop 3.3v, you're at the limit's a 5v would be better that's all.

SurferTim

Are you certain that is a TIP120 (NPN), and not a TIP125 (PNP)? Under these conditions, the TIP125 would keep the LED lit no matter the voltage on the base. Look at the polarity of the collector-emitter diode in the product schematic. Left is NPN, right is PNP.

Just checking...


cheesepower

Oh crap! they are labeled TIP 135  :smiley-eek: But i ordered some TIP120!! The box is labeled TIP120!

SurferTim

That is the problem. It is being lit by the collector-emitter diode. That is why you are seeing 0,5v collector-emitter.


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