Saturday, I went and got some parts for the AC motor speed controller I was going to make for a friend, who supplied me with the stepper motor brackets for the MF 70. When I went to the electronics store, which belong to friends of mine, I came some across huge NEMA 34 stepper motors, and immediately bought 3 of them ($155 total, they were more expensive with S&H from China).
Since I have no suitable power supply (48V – 1000W) or driver boards (7.8A) for them, they will sitting on my shelf for a while. Then I’ll convert my BF20L to a CNC mill.
In the meantime, I started working on the AC motor speed controller, which I found here. The PCB is wrong, so I made my own on Proteus Isis and Ares. The values in he schematic are what I used at first. Here‘s the PCB in PSD format so you can print it on Press’n’Peel at 100% size. Here‘s also the original BMP.
PLEASE BE CAREFUL WITH MAINS POWER. NEVER HANDLE A LIVE CIRCUIT. IF YOU ARE NOT SURE ABOUT WHAT YOU ARE DOING, STAY AWAY! I AM NOT RESPONSIBLE IF YOU GET ELECTROCUTED. THIS CIRCUIT IS FOR 220V AC.
Later on, I copied the PCB prints (I made two boards) on a small piece of Press’n’Peel sheet on my laser printer, ironed the sheet on the copper clad for a while, peel it off when it was cool, etched in Fe(III)Cl, and scrubbed the board with steel-wool under water when it was all done.
After splitting the boards and drilling the holes, I soldered the parts and completed the board. No cables for the pot yet.
The card did not work it was supposed to. The motor was turning weak at some point and that was all. So I changed some parts as rohart suggested in the comments of the same page. I changed C4 to 22nF and R3 to 33K. I didn’t scrap R2 (when I did, it fried the pot at some point), but changed it with a 47K, and replaced the pot with a 50K one. Then it was running pretty smoothly.
All I have is a 15W Orange light bulb and a 19W Ebmpapst cooling fan to test it, until my friend’s 450W motor arrives. I think it will need much better cooling for such a motor. Here’s a video of both. I think I’ll get better results with R2 changed to 33K and the pot changed to 100K. Turn up the volume to hear the motor change speed.
Update: The card was almost ok with my 125W scroll saw, but I had to change C4 back to 100 nF to be able to control my grinder / belt sander, which has a 250W motor on it. I guess it all depends on the motor’s wattage. None of the parts got hot, the TRIAC wasn’t even warm.
I’ll soon try it with my friend’s 450W mini-lathe motor when it arrives.