AC Motor Speed Control Triac PWM 0-cross
February 7, 2013
Hey guys, I am working on the CNC and putting together a speed control system. I went as far as buying a $20 "Router speed controller" which consists of a pot and a BTA41-600B triac basically. The control is terrible and "hiccups" at anything less than 1/2 speed or so.
Obviously, an Arduino would seem to fit in here. I did the googling and I think I am down to one sticky wicket.
- There is a phase issue here and a 0-cross thing where the "PWM'ing" is done at a peak or a valley (I don't know which). It also appears that most circuits invovle an opto-isolator, many of which include this zero-crossover detection.
- Many arduino examples include complex timer set-ups to deal with this zero-crossover stuff
Question: If my circuit includes an optoisolator with zero-crossover detection guts inside, does this take care of all the phase stuff for me and thus, I can PWM like a normal DC motor? If there is a conflict between the phase requirements of the output and the rhythm of the PWM, does the optoisolator zero-cross circuit fix it? Is there a point at which the "harmonics" of both systems kill each other?
Is all the above wrong and I still need the arduino to deal with the phase stuff even if I am using one of these fancy optoisolators?
Is there a better way of doing this? Put simply, I have a router (27,000+ RPM) and I want to slow it down a lot (while keeping my torque if I can) and adjusting speed via uC.