Just stumbled on a motor and controller from a Reebok RX1000 treadmill (c. 2000). Motor is fine. The board is a MC-2000 Rev B; it is divided in two boards. See attached image and schematic pdf. It seems to require a PWM speed signal; not having the original console, I attached a PWM signal generator (as I have done with MC-2100 boards). Currently, the board LEDs light up as follows when powered: On right board, 120Vac, +9V, +5V, and flashing PWM (when signal is on); on left board, 15V (LD1), but not the green HV BUSS (LD3), GATE (LD4), and SPD SIG(LD2). Needless to say, it does not currently send power to the motor leads.

Question: does anyone know the required PWM frequency for this board (I've tried 20Hz as per MC-2100). Of course, the 20Hz could be correct but the board is broken somewhere (I suspect likely). I'm a Newbie, but perhaps the symptoms indicate a likely fault to someone more experienced. Would appreciate any suggestions. Thanks.

 

Are you sure that board requires PWM?
It appears to be the classic SCR bridge set up as per the MC-60/80 for e.g. Not the PWM motor controller as per the MC2100.
I have never had the opportunity to work on a MC2000.
Max.

 

Well, I made surprising progress, tonight. The board now works. At the right board, the Red/White/Black connector was attached in the wrong place; the correct place is HD6.

Notes:
1. The board does not require 20Hz to function; it worked from (but not limited to) 15-200Hz I tried. Surprisingly, it was not sensitive below 20% duty cycle; roughly 500rpm was the lowest adjustable speed. It worked better at 100Hz, with sensitivity down to ~15% duty cycle.

2. When load is applied to the motor, slowing it down, the board responds strongly to bring the speed back up, apparently up to the max volt and amp rating of the motor. It's a bit sluggish in response (it's no servo motor performance, and flywheel is still connected). The speed sensor was not connected. I'll try to rig it up to see if it improves the response, i.e., if the controller has a feedback function via the speed sensor. (The motor is the ubiquitous little 2.5-2.9hp (1.5-1.75hp continuous duty) model.)

 

In testing the speed sensor, I found that it does not appear to provide feedback to the controller to maintain set speed under varying loads. It is just used to indicate speed at the treadmill console. Perhaps the board uses back EMF to maintain speed? Anyway, at above the lowest speeds, speed is corrected fairly quickly. Should be effective for drilling, sawing, and sanding applications. Interestingly, my MC-2100LS-30, a newer board, does not try to maintain speed under varying loads.

 

The MC2100 also sends the sensor direct up to the console, but the processor in the console uses it to correct the PWM control signal it sends back to the motor board.
If using it stand alone, then it has no feedback.
Max.

 

Are you sure that board requires PWM?
It appears to be the classic SCR bridge set up as per the MC-60/80 for e.g. Not the PWM motor controller as per the MC2100.
I have never had the opportunity to work on a MC2000.
Max.

It's not visible in the image, but the 8pin connector is labeled identically to the MC-2100, which can also be seen in the pdf.

 

The MC2100 also sends the sensor direct up to the console, but the processor in the console uses it to correct the PWM control signal it sends back to the motor board.
If using it stand alone, then it has no feedback.
Max.

So, trying to understand, are you saying that the MC-2100 does provide speed compensation for varying loads, but that a component in the console is needed to make it work?

 

The sensor comes into the motor board and goes directly up to the console where the console processor compares it to the set speed, corrects it and sends the adjusted 20hz signal down to the motor board, yours could be the same, if it has a belt sensor.
The MC-60/80 does not have a physical sensor, AFAIK.
Max.

 

Yes, this MC-2000 has a speed sensor, like on the MC-2100, that is positioned at the belt wheel. This I positioned next to a magnet attached to the motor flywheel. The controller reads the pulses but does nothing to adjust the motor speed. But you are saying that the feedback logic to adjust the PWM signal is at the console board? I see. Given the PWM signal is generated at the console, that makes sense. Have you ever isolated that speed feedback component of the console?

 

I have never done anything with the console end, apart from detecting the sensor processing and repaired the main board for alternative uses.
Max.

 

To anyone who has a treadmill with MC-2100, I'd be curious to know if the speed remains constant (or adjusts back quickly) when the motor is loaded. This could be tested by putting pressure on the motor flywheel with your hands (and a rag or gloves), or just by noting the pitch of the motor before and after you first step onto the track. Thanks.

 

My son-in-law has a TM with the MC2100 board and it regulates quite precisely with a varying load.
Max.

 

Ah, great. Thanks!

 

Some information that may be of interest:
I located a console from an Icon Health treadmill that used an MC-2100 controller; I hooked it up to an unrelated treadmill motor I had on the bench; sure enough, the controller tried to maintain speed under varying load, but not very well, creating an increasing under-speed condition up to 10-15% on significant load. That motor is uncommon; the rated HP (2.25 treadmill duty---figure 1.75 cont. duty) is at an uncommonly low 2400rpm.

Could the PID control be calibrated to a specific motor? To find out, I attached an Icon Health motor, the type I recall came with the treadmill console (the ubiquitous, small ~1.75hp cont. duty; see sample image). I repeated the load test and, sure enough, the controller maintained the motor speed quite well. (I suspect that if the speed pulse frequency were greater than 1 per rev, control would be even better.)

Re-testing the MC-2000 controller with it's original motor (same as above; image), the compensation was too aggressive, causing an increasing over-speed condition of 10-15% on significant load.

So, what have we learned? The MC-2000 has the speed compensation circuit built into the board(s); it works albeit a bit unrefined. The MC-2100 speed compensation circuit is partly in the console; it seems calibrated for a specific motor; one has to recreate it (microcontroller, PID and PWM software) if one wants max power at low rpms from theses motors. I'm a newbie. If I stated something incorrectly, please correct me.

 

Don't forget, there is a speed compensate pot on the MC2100 board for setting up the speed for a particular motor.
Max.

 

I thought the speed pot was used to match treadmill speed to the display speed. Are you suggesting that it interacts with PID control as well?

 

The fact it is used by the MC2100 micro, I would assume it is for tuning the actual rpm to the commanded signal.
Max.

 

After some additional experimentation for kicks, I found that the pot setting indeed has an effect on the PID control. However, whether that is its purpose is, think still TBD. Here's what I did:

I connected the unrelated motor mentioned above to the MC-2100. I found the pot was turned all the way CW (max speed adj.). I turned it CCW ~1/8 turn, which reduced the speed I had set from ~570rpm down to 500rpm. I then loaded the motor; the speed dropped and then came back up sluggishly to set speed (500rpm). No more under-speed condition. Cool.

A third thought I had regarding the pot---perhaps a secondary effect---is (wild speculation) that the CW limit setting on the circuit somehow impeded the PID control to adjust fully? Ha, laugh if you must.

 

I have never really delved into the effect of the pot to any degree, just used it to get a little more top-end RPM when using the board for general duty ops.
Max.