Wed 06/17/20 08:51:52 pm
Categories:
Electronics
My first Arduino project: measuring fan RPM.
I recently wrote about measuring the tachometer signal from a fan with an oscilloscope to determine RPM. I mentioned I had some difficulties which led me to some other methods to measure the fan RPM. One of those was to use an Arduino microcontroller.
I based my Arduino project on this example, and updated the sketch to also print the number of pulses counted each second.
Here is the setup using a 12V power supply for the fan and the pull up resistor:
Here is a screenshot of the Arduino IDE Serial Monitor:
The Arduino measured 93 and 94 pulses per second giving 2790-2820 RPM. This agrees with the oscilloscope measurement, and is within tolerance of the 3000 RPM +/- 10% spec. In fact, when I did the oscilloscope test the frequency measurement fluctuated between 93 and 94 Hz so the results are consistent.
Next here is the setup using the Arduino 5V power supply for the fan and the pull up resistor:
Here is the result:
The Arduino measured 43 and 44 pulses per second giving 1290-1320 RPM. As I mentioned in the oscilloscope post, there is no RPM spec for powering the fan with 5V but I wanted the measurement anyway. The reason was to compare it the Arduino result…and fortunately the results are consistent and agree.
The setup for using the Arduino 3.3V power supply looks the same as the setup using the 5V supply. Here is the result:
The Arduino measures 26-28 pulses per second giving 780-840 RPM. Again, this is in agreement and consistent with the oscilloscope measurement.
When I first had problems using the oscilloscope to measure the fan speed I looked into getting a new multimeter with a frequency measurement capability. Then I found out I could get an Arduino for less than the cost of one of these multimeters. I have wanted to try out microcontrollers for years. Finally, this was the perfect motivation to get started.
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