Please help

296

03:34:11

I know i'm doing lot of questions :p but that's just because i don't know most of the formulas so i can't solve lot of my problems when i'm building something. So the question is if i have a matrix with powerful leds and i can't use them directly with arduino so where do i need transistors on anode or chatode of the leds? Please comment if you know the answer 
- nikisalli 

published 10 years ago

Karsten

10 years ago

ElectroDroid can help you with some of the formulas.

EvilDuck95

10 years ago

Really, it shouldn't matter, typically I just connect them to ground via the transistor from their cathode. You're only opening the transistor with the Arduino via the Base pin, after that, it behaves like a wire.

nikisalli

10 years ago

I already have that app but sometimes that's not enough

ferlop

10 years ago

Normally you connect the led to the collector of NPN and to the emmiter of PNP.

ferlop

10 years ago

I Have to make a correction, transistor in both transistor types you connect the led to the collector.

AmitTirkey

10 years ago

Both the way you can connect the LED according to transistor type NPN(-) or PNP(+)

hurz

10 years ago

Niki, collector and emitter of PNPs have to be swapped. Increase base resistors to e.g. 1kOhm. Problem is the missing current limiting resistor for LEDs. One solution within simulation would be reduce the DC supply to about 2.3V were 0.3 is two times 0.15 saturation of both transistors and 2V for LED. In reality is quite problematic...

nikisalli

10 years ago

Thank you all guys now it works better :-)

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