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Topic: Hi guys, question about driving something by mP (Read 893 times) previous topic - next topic

goldami1

Hi friends,
I have tried to drive a usual trimmer by a microcontroller with an NPN transistor but from some reason, it doesn't work!!!!
Here take a look:

V2>V1
My goal is to control this trimmer that is located and connected on another circuit with that microcontroller.
By this arrengment I tried to use the transistor as a switch and decide when I want the current to pass through the trimmer and when I don't.
But from some annoying reason, it doesn't happen, it doesn't work!!!
please help.

P.S
the way I tried to make it work is just to send "1" logic to the transistor and in that way to cause the transistor to pass the current through the trimmer (to connect the trimmer to the rest of the circuit).


Thanks in advanced,
Have a nice week,
Ami.

Grumpy_Mike

Sorry there is simply not enough of the schematic to tell anything about it.
You draw a NPN transistor but label it PNP.
Where are the grounds connected?
What potentials are the other circuits at?

goldami1

sorry for my mistake,
It's a NPN one and V2 is about 2.5v while V1 is connected where the voltage is 1.6v .

goldami1

just to make sure, I want to use the transistor exactly like realys been used.
pretened for yourselves there is a rellay that Is controlled by the mP and once, the rellay enable the trimmer so the current will pass through it, and once it doesn't allow the current to pass through that trimmer.
That's it, all the difference is in the part. instead of using a rellay, I want to make it happen with a transistor.

I still wait for any kind of an answer.
please help.

elandd2011

You have to use something like this where R2 is the circuit you want to switch on and off but
1- Transistor must be powerful enough  to drive your circuit, you have to know the amount of current you need
2-The base current must be limited to 20ma so the transistor must have enough hfe ( current gain) for do that
3-For full help i need to know how much current you need and the input voltage

Grumpy_Mike

Quote
But from some annoying reason, it doesn't happen, it doesn't work!!

You have to connect the ground on the Arduino to the ground on your other circuit.

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