Qualin:
Yes, Use the original timer for the other operations of the machine. Yes, I could have used just relay logic with timed relays and the such for signaling the VFD, however I want to be able to change the tumble and spin sequences. Using just the relay logic won't allow me to do that as easily, also remember that I have removed the speed changing gear motor. The current modification does not include the leg switch for detecting out of balance conditions. The PLC will allow me to incorporate that feature with just some wiring and a programming change. If you have anymore questions, just post them. We will step through them!
1966_mustang:
For the pump, it has its own contactor, if you look above to post# 562708. The original motor was reversible. I use the wire to make the motor reverse during spin and condense to fire the contactor for the pump. As I now remember, I'll have to rewire it as I am also using these same lines to supply the pump, when I really just want to use the wire fire the contactor,and the supply to the pump should come direct from the terminal block of the machine.
You bring up a good point about using a DC motor. Building my own controller for it is quite involved. There are several ways to do it. Interestingly, a friend and I are currently working on building a controller for a zero-torque 3 phase BLDC motor. For the phase switching, one could use an H-bridge, as it already has the transistors and the diodes to protect them. You can also use a circuit of 3 MOSFETS, or a circuit of 6 MOSFETS, use a massive Bridge rectifier and capacitor bank so that the supply stays constant under load. Then use a micro controller like a PIC 18 or arduino to fire the MOSFETS. The problem of the BLDC motor is that you have to know when to fire the MOSFETS. This is dependent on the rotation position of the motor. The rotation position is always subject to change due to load. If the firing of the MOSFETS or IGBTs is not on cue with the rotation position, you get a break-down in speed and a stalled motor. To correct this problem, you can use a hall-effect sensor, or go the vector-less approach. The vector-less approach is is somewhat complicated, as you have to detect the zero-crossing moment as the shaft of the motor rotates. This involves building a low-pass filter that is good enough to discard the other noise, due to the switching frequency of the MOSFETS, spikes, and other transients that ride in the system. Then you must detect the zero-crossing moment in the bief moment that the MOSFETS, IGBTs are switched off and the motor becomes a generator. Take that signal, convert it to a digital signal that the micro-controller can deal with, then fire the MOSFETS, IGBTs appropritely. Use a capacitor switching circuit to start the motor.
It is very possible to do this, but complicated. For that, baby steps first. I do small-scale implementation first, then tackle a project building a controller for say a 1hp TEFC BLDC motor.
