Basically, I need to measure the RPM of a servo motor without arduino and then verify the results with arduino. How can I do it
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\$\begingroup\$ How accurately do you need to measure the RPMs of the motor? And over what kind of range? \$\endgroup\$– SteveShCommented Jul 2, 2022 at 12:15
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\$\begingroup\$ What type of 'servo motor' is it? \$\endgroup\$– Bruce AbbottCommented Jul 2, 2022 at 12:22
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\$\begingroup\$ A traditional DC motor with brushes and permanent magnet can be its own r.p.m sensor at the same time. The induced voltage is proportional to r.p.m, only compensate the voltage drop in the winding resistance. That has been nothing special after low cost opamps became widely available 50 years ago. \$\endgroup\$– user136077Commented Jul 2, 2022 at 13:21
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If you have an oscilloscope, use it to look at the step motor drive, and divide the frequency you see by the steps per rotation.
Or, if you have an oscilloscope, stick a little magnet on the motor shaft, wind a little coil, hold it near the shaft, and see the voltage from the coil on the scope. 1 pulse per rotation.
Or, if you have a piece of thread, tape one end to the motor shaft. Start the motor and run it for ten seconds, and measure how much thread has spooled up on the shaft. Calculate how many turns that is. Or just count the turns as you unwind the thread.
Or, buy an RPM meter from Amazon, about $15.
With the Arduino, you'll have to explain more what you need to know.
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\$\begingroup\$ Or use an optical gate or reflector and hook it up to a counter. \$\endgroup\$– RalphCommented Jul 2, 2022 at 11:40
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1\$\begingroup\$ OP didn't say anything about it being a step motor drive. So you might want to caveat that part of the answer, \$\endgroup\$– SteveShCommented Jul 2, 2022 at 12:13
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\$\begingroup\$ Servo are generally DC motors. \$\endgroup\$ Commented Jul 2, 2022 at 13:33