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What am I doing wrong ??? Arduino - tachometer !? Answered

Hello ... I would like to ask, what am I doing wrong. I'm trying to create this instructable www.instructables.com/id/Arduino-Based-Optical-Tachometer/ ...

I downloaded the code, created the circuit (photo provided) ... and I'm using these components :
 1. IR LED = SFH487-3 www.maplin.co.uk/module.aspx (code CY88)
 2. Phototransistor = SFH300-3 www.maplin.co.uk/module.aspx (code NP64)
Resistors are the same value, like in the instructable.

Please, could you tell me, what am I doing wrong ???

Thank you very much.

Zholy

P.S. : IR LED is working, the PhotoTransistor is working as well <- I tried to measure it with my voltmeter - for CONTINUITY ... and as I was getting closer to the IR light, the value was decreasing.

Discussions

The headline circuit is wrong, very wrong. The phototransistor is wrong.

Put the 10K to +5v, then to the transistor collector, then tie the emitter to ground. Pick the signal for the arduino off from the collector. 


Steve

Thank you very much ... it's like you wrote. Now I remember, that I did the same with the LDR :( ...

Thank you.