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Topic: Correct transistor wiring (Read 1 time) previous topic - next topic

illillillill

I have my arduino feeding a digitalWrite(50, HIGH) to my transistors "Base" leg,  and now i want that transistor to control a power supply for a relay,  how would you guys wire that up ? . right now i collect the volt from the PSU and emit it to the relay,  and on the other side of the relay i have a wire connected to ground on the arduino.   it's making the relay do some clicky noises but it doesent have enough power to make it switch.  my PSU goes from 0-30 volts,  tried turning it all up, no change. if i wire it directly to the psu i can control the relay manually,  but then my arduino cant control it.  please haalp :(

breagle

http://www.arduino.cc/playground/uploads/Learning/relays.pdf

This should help with how to wire it. Make sure to use a diode as show. Running a relay straight from your arduino is bad for it. The coil builds up high voltage spike that is put into our arduino. The sketch you need is a simple switch one.

illillillill

i cant see what it says on the 2 components on teh far right. exept "R"  rest of teh text goes outside the picture :(

and yea i already have a diode on it :) fried tons of transistors already because i missed the diode :b

breagle

You need a resistor on the base of the transistor to the arduino.

illillillill

i have that,  400 some thing ohm,  should be enough ?

illillillill

i just noticed that this schematic is for small 5v relays,  mines a 10v , and the arduino cant produce enough power to trigger the switch, so back to my original question,  how do i wire the PSU correctly to the transistor or relay. ?

breagle

PSU to relay/diode. Then relay/diode to collector side of a NPN transistor. Emitter to ground. A resistor to the base from the arduino. Connect your grounds of the PSU and arduino. This assumes you have a NPN transistor.

illillillill

i have a bc547 so yea, npn,  and i just wired exactly like u said.  still nothing happens.

illillillill

ok i made it work,  i forgot to wire the minus side of the psu to the arduino ground.

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