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I am working on Process Control Chapter 5 Activity #2, PWM Test. I can not get the sensor to read the RPM of the fan. I am sure the code is correct ,
or at least identical to the text code , because I copyed and pasted it. I'm sure the circuit is correct, because the sensor works when I use the
Tachometer code from Chapter #4.
I suspect there is an error in the program titled PWM Test; as I have foud errors in other programs.However, I can not find it. Please help if you can.
06-15-2011, 03:11 AM
If you could "attach" the actual program code you are using (not the code in the book) it would help. Also include a description of where things are connected and how they are powered.
Thank you for the reply.
I hope the code attached sucessfully; I'm afraid I may have only attached the name of the file. I will have to rewire the circuit, as I have moved on to the next activity.
How exactly do you want me to describe the circuit. Maybe by bread board points? On a bread board with 17 rows labled 1-17 and 10 columns labled A-J. That seems awfully cyrptic and hard to follow. Or just a "long-
hand" type description ,as: collector of photoresistor to vdd(5-volts) through a 220 ohm resistor. Both seem tedious and confusing. Is there another way?
06-16-2011, 03:03 AM
Do you have stamp plot installed and configured and what is it you get when you run the program?
I have typed two rather lengthly replies only to be informed that I was not logged on when I was. Enough for now; I will try again later. But yes StamPlot is working as expected, the program works as expected. Except for the RPM
To anyone else who is having a problem with this activity, I figured out what was wrong.
I kept waiting for the RPM indicator to display the RPM of the fan. Doesn't work that way. The message box displays the fan rpm as a quick shot frozen type number. If the message box displays zero, you have to press enter to reset it,and adjust the fan distance from the sensor. When a good number comes up in the message box enter 1 in the message box and hit the enter key. Then the indicator starts displaying rpm and the program plots the duty cycle and rpm in the plot area.
If any one has trouble with this just post and I will try to explain in more detail. The instructions in the text through me way off.
Thanks for following though and posting your findings.
I'm sure it will help others in the future.