Just one correction:
"This is PWM because whatever the waveform, the voltage is turned off at some point. If the voltage to the motor does not go to zero, that is not strictly PWM motor control. I believe this is correct."
This is not true. Because PWM can only be a square-wave drive to dc motor.
If this controller does not present a square-wave drive to the motor, it's not strictly a PWM controller. It seems.
"it determines the set speed of the motor." Better said as, it determines the width of the pulse which determines the set speed of the motor.
My WAG is the trianglewave rides up or down on the DC voltage that comes from the computer. In other words, The .www.cpemma.co circuit adjusts the DC level to set the pulse width. The www. electronic design circuit adjusts the voltage the triangle wave rides on to set the pulse width. The trianglewave could be 3volts in amplitude and run from 0 volts to 3 volts or run from 2 volts to 5 volts. Dependent on the DC input from the computer.
Well ya it does, as Rich Grise pointed out, "The Schmitt trigger (lower left) produces a triangle wave, which is summed with the DC input (yes, "input voltage from computer" is DC.) by the 10K and the 4.7 uF.
After all off that, I went and read the article, everything I said is correct but probably NOT, if you apply it to this circuit. Someone else with more knowledge is going to have to describe the operation of this circuit. I'm not sure that this is a PWM circuit. Mike
I'm trying to get back into electronics, but I seem to have picked a difficult circuit to understand. :c) I'm actually wanting to make a speed control with PWM that maintains constant speed.
If you are curious enough go to sci.electronics.basics look at the thread "What passes as Pulse Width Modulation in DC Motor Control?" I'm hoping someone there will be able say whether it is a PWM controller.
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