I'm using a motor from Adafruit. (Product page link: https://www.adafruit.com/product/1201)
I measured the frequency of vibration with different voltages, but the frequencies are quite different from the frequency shown in the product page. According to the product page, the frequency of vibration is 11000RPM (around 183Hz) with 5V. However, I got only around 58Hz with 5V. I think I did some mistake in measuring the frequency, but I don't know what is the problem.
Here is what I did.
- I made a simple circuit with small resistor (1.5 ohm) and a motor. The resistor and the motor are connected serially.
5V was applied between two terminals (A - 5V, B - GND) with a power supply. At this point, 105~110mA current flows through the resistor.
I used an oscilloscope to read the current through the resistor. The oscilloscope showed a wave form.
I calculated the number of peaks for one second. There were around 700 peaks in 1 second.
A rotation of a motor makes multiple peaks in the current wave. The number of peaks per rotation is twice of the number of commutator in the motor. As far as I know, the number of commutator in this motor is 6, so the number of peaks per rotation is 12.
I divided the number of peaks for one second by 12, and got around 58 Hz. That's it.
I think I made a mistake on this process because the number I got is quite different from the number in the product page. Please help me finding the mistake.