Without disassembling the motor, is there a way to determine how many pulses per rotation that a rotary encoder has. I have an operational high torque window lift motor with a single output encoder. It has worm gear reduction. The secondary gear has 74 teeth. It also has a limit switch built into the gear case. I have not been able to find a datasheet on this motor which is made in China.
Write a sketch to detect pulses, turn the motor one revolution and count the pulses ?
Because the motor is connected to a worm gear transmission it's not possible to turn the motor without disassembly.
Seems like it would be equally useful to know the pulses per revolution of the gearbox output shaft, which you can observe directly.
I tried that by counting the pulses of a full rotation. However, my observations had varying results. When I applied full power to the motor for one second, I counted 528 pulses. But when I applied one half power, I counted 222 pulses when I expected to get 264. If too little power is applied the shaft won't spin at all. I'm trying to come up with a PPR for a PID controller, so I need an accurate determination.
Put a pointer on the output shaft, and count the pulses for 10 revolutions. Divide the result by 10. Or maybe for 100. Repeat until you reach a consensus, or "good enough". The PID algorithm doesn't care.
Ah yes! That's a good idea. That should help to reduce the error. So then I take the average and round off the error and divide by 74? I'm I correct?
Why do you think the PPR of the motor shaft is important, and not the PPR for the gearbox output shaft?
What will the PID do in your project, if not determine the rotational speed or position of the output shaft?
I'm assuming it is important because I acquired a PID sketch online and it has a PPR variable that needs to be populated. I am in the process of modifying it for my experiment. It's purpose is to determine rotational speed and position.
Sounds like you need to think this through.
True, unfortunately I tend to think it through one piece at a time. It's so puzzling 
74? Where did 74 come from?
74 is the number of teeth on the gear inside the worm gear transmission.
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