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I'm trying to measure the speed of a small DC motor using a rotary encoder and an OPTO sensor, and counter input on myDAQ.

Here's my circuit on the breadboard: enter image description here

enter image description here

enter image description here

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The collector pin of the transistor is connected to the DIO1 port of the myDAQ.

And here's the LabVIEW code:

enter image description here

On the front panel, I only have the RPM numeric indicator.

When I run the program, with the rotary encoder spinning in the gap of the OPTO coupler, nothing happens. The RPM numeric indicator keeps showing 0.

I thought the problem was my OPTO coupler. I tested it through analog input and I successfully visualised the pulses, as shown here:

enter image description here

So the problem is not the OPTO coupler.

And I can't seem to figure out the source of the problem. I would really appreciate some help please.

Charbel Nicolas
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    Amplitude of **-5V**? I notice that breadboard connections to MyDaq use **blk** and **red** wires to the 5V power source. We usually connect **blk** to **GND** and **red** to **+5V**. You haven't followed this convention. – glen_geek Nov 27 '22 at 13:53
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    Show a schematic. Breadboard pictures do not constitute a circuit diagram. – Andy aka Nov 27 '22 at 14:11
  • Optocoupler is a word, not an abbreviation. There's no need to capitalize it or split it into two words. – Hearth Nov 27 '22 at 18:31

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