It has been working for three years in my grandmother's juicer, I used an all plastic potentiometer to bring the control out, a rubber grommet acts as a seal between the potentiometer shaft and the container.
I answer so we eliminate doubts R5 regulates the revolutions while R14 serves as a calibration. It must be calibrated to have the complete excursion of R5 between maximum and minimum without points where you rotate the pin and you have no change. It is better to do the first tests with a lamp to visually have the effect of the calibrations. Once the calibration has been carried out, check that the triac is cold. If so, the circuit is ready to drive the motor
I stretch a little speech…
I have done some research and it is determined that the brush motors (like that of my drill and other power tools) they can also run in direct current. This is why they are called universal motors. I also noticed a certain project, which is the rough way of a VFD, the alternating current is rectified. Others using a battery run a washing machine motor, but it is not clear whether he has enough torque.
Well the result makes me think that you can possibly convert the mains voltage to DC and modulate the output in a rather square shape. Of course the ACPWM is perhaps the result par excellence.
I also saw a project that uses a 555 and an IGBT to create the ACPWM.
Do you have any information?
Yes, the universal type brush motors also work in DC but to power them you have to get an SMPS like the one I'm trying to make myself… Find the progress in the forum and hope to have time to complete in the next few days.
Of course it is a much more complex circuit than the one proposed above.