QRB1114 sensor question?
Jeronimo
Posts: 3
I am doing activity #2, CH 5 (High Current Drive and PWM control) from the Process Control student guide and I am having problems because it is not displaying %RPM on the stampPlot (it says that the %RPM is 0). The part of the circuit that controls the speed of the fan is working fine, and I followed the diagram carefully it should be exactly like the diagram provided but I still don't know what is wrong. I had done the Tachometer exercise from the same book and it was working fine. I also checked the output from the sensor and measured 4.2V coming out of it, and 1.2V input to the emitter. How can I troubleshoot the QRB1114 sensor? or what else can I do to check the circuit?
Comments
I encourage you to do so now at:
www.parallax.com/Portals/0/Downloads/docs/prod/sic/PCv1.0Errata-v1.0.pdf
Activity #1 in Chapter 4 shows how to test the QRB1114 sensor.
Using a DVM, monitor the collector voltage of the photo transistor and slowly
bringing a white piece of paper near it. You should see the voltage drop as
the paper gets near the sensor and the photo transistor begins to conduct
as a result of the reflected IR light.
If that works okay, do Activity #6 in Chapter 4 and let us know if that
works.
The idea in this method of troubleshooting is to go back to a situation
where the circuit worked and then SLOWLY make changes until you run into
the original problem.
phil