Treadmill motor controller schematic at dropbox retired

URL?

I'm still here but I'm pretty far from a expert compared to most of this group. I just reverse engineered the schematic from the board.

As for the values of R2 and R4 they should be on the schematic. At least they're on the copy that I've got in front of me right now (you're lucky that I just cleaned up my office and happened to find my copy a couple of days ago). According to this one R2 is 4K and R4 is

L1 is a torrodial choke and I've not got any clue what it's rated at. It is one of several components on the board that would be difficult to source but could probably be worked around by somebody with more electronics engineering experience than I have.

Keep in mind that there's a resister not shown on the schematic and not obvious when looking at the board. It's in the form of one of the traces on the board itself. It snakes around to make for a low value high capacity resistor in the power portion of the circuit.

The big problem you'll have is that this controller needs a tachometer on the motor to function properly. That might be hard to add to a router.

The fact is that I'm not to one who came up with any of the modifications to the board. I just had the time to make up the schematic by tracing the board (wish I had that kind of free time now days). I then posted it and let others do the figuring on how to modify it.

Wayne Cook Shamrock, TX

L1 is probably just a hash filter, value not critical.

Check the application example schematic on the TDA1085 datasheet. It's somewhat simpler than the treadmill motor controller and presumably works. No L1 at all in that schematic, no transistors either. The datasheet from ON Semi even has a PC board layout. You'd probably need to change some values to work with a treadmill motor, because the datasheet design is for a 0 to 15K RPM motor used in a washing machine. .

There's another chip, the TDA1185A, that is designed for control of universal motors with no tacho feedback, but I think it's no longer in production. You might find some still floating around with some diligent netsurfing. I have a few of them in my goodiebox I'm saving for sewing machine speed controls (Singer Featherweight and Singer 401) when I get around to it. One is reserved with Fitch's name on it for his Singer Featherweight when he gets around to it. Nothing Is Urgent.

You can buy a 15-amp router speed control for about $25 from Rockler. It's probably not as good as something based on a TDA1185, but it works better than I expected it would. It claims to employ some voltage feedback speed sensing. I sure don't see it in the extremely simple circuit, but Jeff Wisnia recalled a similar circuit and reference to voltage feedback in the old GE SCR Manual circa late '60's or early '70's. I found the circuit in my old SCR manual and that indeed is what they're doing. It's not nearly as "stiff" as a control would be with tacho feedback or current sensing as the TDA1185 employed, but it's suprisingly good for such a simple circuit.

The best speed control would be achieved if you could devise a way to add a tacho speedsensor to your router.

This really isn't a good controller for a lot of motors - it was matched to the original GE open frame AC/DC motor, and has soft start which will fight with any soft-start router. The values for time delay can be changed (prob'ly in the drop box), but I'd go for a dedicated speed control. I CERTAINLY wouldn't try to BUILD the one shown....

Harbor Freight had their 25.00 control on for 12 dollars recently... /mark

Richard J K>