Another Treadmill Conversion

[FanMan]

There are a few "treadmill conversion" threads here with varying amounts of information, but I thought I'd summarize my own experiences here in one single thread as I progress. As of this writing, it's still a work in progress:

I've wanted for awhile to convert my Jet 15 mill/drill to a variable speed drive to avoid the hassle of moving the belts around. My shop is so cluttered it's hard to get around to the back of the mill to move the belts. Anyway, a few weeks ago I found a free treadmill... free because the particle board slider bed had cracked but electrically it was in perfect condition.

After getting it home and verifying everything worked, I ripped it apart. The motor nameplate says "2.80HP treadmill duty @ 130VDC, 2.60HP cont. duty @ 110VDC/1940 Watts". As my mill has a 1HP AC motor that should work fine. The motor control board, however, is a MC-2100, which is a little trickier to interface than the older MC-60 that only requires a speed control pot. The MC-2100 is expecting a PWM (pulse width modulated) signal from the treadmil control board to set the speed. Fortunately, there are a number of websites with information on how to do this. Warning if you're not reasonably electronics savvy, you'd be better off with the MC-60 or a commercial DC motor controller.

I decided to use the "Sons of Invention" dual 555 timer circuit:


After taking inventory of my electronics junk box, I placed an order from Digikey for everything I didn't already have. Once the order arrived and I had time to play, I put it all together on an old Radio Shack breadboard... and spent most of a day trying to get it to work. Part of my troubles were simple wiring errors, but in the end I had to change a few components. The 27K resistor going to the trim pot didn't do it for me, but a 33K did. I also added an led (with dropping resistor) to the pin 3 output from the first timer. Pointing my old Heathkit "Thumb" Tach (an optical tachometer for model airplanes) at the LED let me check the frequency. I also hooked the 16Hz output (that goes to the blue wire) to a small speaker at one point to verify it was working.



Anyway, I finally got it working, then made a permanent board on a Sparkfun breadboard that was in my Digikey order. Once it was all together, I tested it all... the motor goes from some speed too low for the Heathkit tach to measure up to around 6000 rpm.



Along the way, I neglected to secure the motor properly so it fell on the floor, shattering the cooling fan... I'll have to work out a replacement.

The flywheel / pulley attaches to the motor shaft with a left hand thread. Everything I've seen online makes it sound like it should be a piece of cake to unscrew it. Yeah right. Even with the broken fan removed and the back of the shaft clamped in a vise, it's not coming loose. Although I wanted to remove the flywheel entirely, I don't want to damage the motor trying to remove it, so I'm going to try to use it as it is. The poly-v bent pulley on the motor is roughly 1 1/8" diameter and straight sided, so the plan is to bore out a v-belt pulley to fit over the poly-v pulley.

It's said some of these motors have angled brushes so they'll work better in one direction than the other, but mine appear straight and the motor turns the same speed in either direction.

Part of today was spent hacking up a Tripp Lite UPS case to hold the motor control board and some associated wiring.

 

[QCaudill]

So if the motor happens to be a CCW rotation instead of CW the threads on the flywheel would be R handed instead of L handed wouldn't they? Just a thought.

Sent from my SM-N920P using Tapatalk

 

[FanMan]

I guess so, but I've never seen any mention of one with RH threads.

 

[FOMOGO]

That's a pretty stout motor, must be from a commercial treadmill. I found one used for my wife a few years back and I think she would be a little upset if I commandeered it. I'm betting your really going to like that kind of rpm range and torque, but you may have to upgrade the spindle bearings to take full advantage of the top end potential. Let us know when you have it up and running. Mike

 

[MozamPete]

Will be watching with interest - I brought a non functioning treadmill to use for a mill conversion a while ago, but I had to try and fix it and then the family wanted to use it.
They seem to have lost interest now so when it had to be moved to put up the Christmas tree I took the opportunity to tear it apart. Have bench tested the motor but similar to yours it need an 'electronic' signal from the controller board on the handles to set the speed - haven't look in detail what this signal is but it is about a 20 core ribbon cable. Also has a very slow speed ramp up rate which could get frustrating. I was just planning to buy a generic controller, but you may inspire me to try and use the existing controller and build a new interface.

 

[hman]

Fan Man -
Thanks so much for the schematic! Now I'll know how I can make use of an MC-2100 controller if I run across one. I've kinda avoided used treadmills in the last few years, because I'd been afraid they no longer had the MC-60, which is all I knew how to wire up.

PS - Your post inspired me to do some more looking, and indeed the dual 555 circuit is "out there." One interesting site I found suggested adding a capacitor across the + and - rails, also adding an NC momentary switch between +12 and the end of the speed pot.

 

[FanMan]

Fan Man -
Thanks so much for the schematic! Now I'll know how I can make use of an MC-2100 controller if I run across one. I've kinda avoided used treadmills in the last few years, because I'd been afraid they no longer had the MC-60, which is all I knew how to wire up.

PS - Your post inspired me to do some more looking, and indeed the dual 555 circuit is "out there." One interesting site I found suggested adding a capacitor across the + and - rails, also adding an NC momentary switch between +12 and the end of the speed pot.

Yeah, I saw that schematic, too. Mine worked without the extra capacitor, and I found putting the momentary switch where they show it (adjacent to the trim pot) did nothing... maybe it really should have been the speed pot. However, putting the NC momentary switch on the red wire (main power to the timer board) does the trick. Seems the motor controller won't start unless the timer signal comes on after the controller has started up.

But get some extra resistors if you do... as I said the 27K didn't do it; it took about 42K total (the 33K resistor instead of the 27K plus most of the 10K trim pot) to dial in the right frequency.

You can get MC-60's on ebay for $40-60. Just before I got the 2100 working I was getting so frustrated I was tempted to chuck it and just buy a -60.

With all the frustration, if I was doing it again I think I'd go for the Arduino version. I've never worked with Arduinos before, but it's probably about time I did.

Tonight I cut the hole in the switch box for the tach, and wired the reversing switch. Still debating on some of the wiring... the plan, as of the moment, is to keep the mill's existing start/stop to switch everything on and off, with the NC button to start the motor. The motor controller will provide 12VDC to the timer board, and I already have a separate 12VDC power supply that powers the lights that illuminate the DRO displays... I figure to use that power supply now for the tach and motor fan. As I said above I broke the original motor fan, so I'm going to use a 12V fan instead of putting it on the motor shaft, which has the advantage of blowing in the right direction even if the motor is running in reverse. I'm just debating if I really want the display lights to switch off when the mill's motor stops... but it will simplify the wiring, and I can always switch the power back on as the motor won't start again until I push the start button.

 

[FanMan]

Slow progress... last night I finished wiring the lower box that holds the motor controller; the upper box is done except for the 12V accessory wiring:



It's made more complicated by the way I'm doing it... I'm using the enclosure from a dead Tripp Lite battery UPS, which was just the right size to hold the control board. Because the UPS had six power outlets, I decided to use them, and reduce the extension cord clutter around the machine. Three of the outlets will be unswitched, and the other three will be switched by the mil power. At the same time, I want to continue to use the mill's original power switch on the front of the head. As such, the power cord comes into the box and is directly connected to one set of outlets and a power cable going to the head. Another cable returns the switched power back to the box, with a tap along the way for a 12V power supply that will power the tachometer, the DRO lights, and the replacement motor fan (I wasn't sure the motor controller 12V supply was sufficient for all that). The motor wires (0-130VDCDC power from the controller and the thermal switch) go out a separate conduit to the motor, and finally the signal wires from the controller to the timer board, which is in the upper box with the speed control pot, reset/start button, and tach. After getting everything hooked up, I plugged it in (without the motor) and verified that the light on the control board was still blinking as it's supposed to.

Next is to make the motor mount. A friend is boring the new pulley for me, since I don't have a lathe and he can do it far easier than I could with the rotary table on the mill.

 

[FanMan]

Progress tonight... my buddy bored out the pulley to 1.107" (the OD of the poly-v belt on the flywheel) for me. He also turned down the OD to 3" since it was an A/B belt pulley and the A section belt on my mill was considerably inside the OD. It wouldn't quite go onto the motor, which I expected, so I powered up the motor and hit it with a file. Took about a thou off and it slipped right on, filed a flat for the set screw and that part is done:



Once that was done, time to mount the motor, so I removed the original motor and slipped the new motor down through the hole in the belt guard... it barely fit, and there's just enough room to move the motor between loose enough to remove the belt and tight enough to run. Unfortunately, though, the lip around the hole is a bit too high to get the flywheel down enough to put the pulley in the right place, which I expected (or feared), so I removed the guard. Took a bit to figure out how to get the spindle pulley off, I didn't want to crank on it with a puller and risk damaging it, but it turned out with a puller hand tightened I was able to break it loose by moving the spindle... it was a taper fit and not that tight. Once the pulley was off the lower guard came off easily.

I'm going to use the original spindle and intermediate step pulleys and belts. With the belt on the new motor pulley in the second-from-the-bottom location and assuming 200-5700 motor rpm, I'll have 143-4042 or 103-3031 rpm at the spindle with the front belt in the upper grooves, or 43-1192 if I move the front belt below the motor belt.

I epoxied a magnet (for the tachometer) to the underside of the spindle pulley with JB weld, then drilled a hole in the lower guardp for the proximity sensor for the tach. Not sure yet how I'm going to machine down the lip on the hole... it's about 1/2" high and I need to remove about half of that. I could just cut it out with a Sawzall, but I'd like to retain at least part of the lip for the stiffness it provides. Can't mill it out, unless I put the old motor back on the mill, which I'd rather not do at this point. But I'd had enough for one night, so I'll think about it overnight.

 

[markba633csi]

I'm not surprised no power supply decoupling (filter) cap was shown in the original circuit- It's assumed if you have worked with 555s before you would know to add one.
If it seems to work without one you should add it anyway because the circuit may be unstable without it. I would actually add more, say, 10uf/25volt.
MS