hantto
Member
Hi!
I recently bought a line following robot FK1108 made by Future Kit. See attached manual and photo. The stock circuit is works ok, but I thought about making an enhanced circuit with H-bridges and microcontroller and so on.
To make a speed controller I would need to measure the rotation speed of the DC motors. I thought about detecting the noise of the brushes, but that won't work reliably because I intend to use PWM to controll the speed.
The obvious solution would be to put photodiodes and leds at each side of the wheels and use the spokes as optical interrupters. That would probably work well, but the measurement rate would be quite low, especially at low speeds. The ideal situation would be to measure the rotation speed of the motor shafts directly. The problem with that is that the only portion of the shaft that is accessible of the motors is about 0.5 mm long at the back. That is too short to attach an optical interruptor disk. I thought about maybe using a hall-sensor to detect the changes in the magnetic field, but because it is a DC motor, the magnet field is stationary. So I don't think that would work either.
Do you have any ideas over how I could measure the rotation speed with a decent measurement rate?
I recently bought a line following robot FK1108 made by Future Kit. See attached manual and photo. The stock circuit is works ok, but I thought about making an enhanced circuit with H-bridges and microcontroller and so on.
To make a speed controller I would need to measure the rotation speed of the DC motors. I thought about detecting the noise of the brushes, but that won't work reliably because I intend to use PWM to controll the speed.
The obvious solution would be to put photodiodes and leds at each side of the wheels and use the spokes as optical interrupters. That would probably work well, but the measurement rate would be quite low, especially at low speeds. The ideal situation would be to measure the rotation speed of the motor shafts directly. The problem with that is that the only portion of the shaft that is accessible of the motors is about 0.5 mm long at the back. That is too short to attach an optical interruptor disk. I thought about maybe using a hall-sensor to detect the changes in the magnetic field, but because it is a DC motor, the magnet field is stationary. So I don't think that would work either.
Do you have any ideas over how I could measure the rotation speed with a decent measurement rate?
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