Bypassing digital control panel. PM dc motor to AC variable speed control. How?

Thread Starter

Ratisse

Joined Jul 11, 2020
6
I acquired a True 500 soft system treadmill a couple days ago. Wanted the parts to power a lathe and other power tools.

I hooked up the main board, control panel and drive motor. Tested out the drive motor through engineering mode. Works fine.

The plan is to build a variable dc power supply incorporating a tachometer with LED displays for both power and motor rpm.

Since the board already converts AC to DC, I was hoping to eliminate the treadmill's original control panel and digital display.

Was hoping someone had input on where to tap into the board with a linear rotary potentiometer, LED tachometer and voltmeter display.

Thank you in advance for any input.

IMG_5887.PNG
IMG_5890.JPG
IMG_5889.JPG
IMG_5888.JPG
 

Thread Starter

Ratisse

Joined Jul 11, 2020
6
I understand there might be a hesitation to reply either because that was my first post, lack of knowing my background, that the solution might be simple and I'm overlooking it, etc.

My background with electronics is basic. Did a year in college on the subject (lots of formulas, math, building basic circuits on a bread board and testing them).

With everything else, my background is in electrical, metalwork, woodworking, leathercraft, a bit of welding and building simple machine systems.

I know I could call it a day if I just pick up a SCR speed controller, swap the potentiometer out, add a bridge rectifier, include LED tachometer/voltage display and switches.

Here's pics of the motor and control panel.

IMG_5894.JPG
IMG_5893.JPGIMG_5892.JPG
 

Papabravo

Joined Feb 24, 2006
13,968
If I had designed the board, or had a schematic diagram I might be able to help. Lacking either of those makes it pretty hard. It would be a good deal easier to design what you need from scratch without having to work with scrounged parts.
 

MaxHeadRoom

Joined Jul 18, 2013
20,927
Typically T.M. manuf. do not provide schematics, as they are proprietary usually.
If you have it hooked up and working with the original control, then the only hope is to do some reverse engineering and go from there to use the board on its own.
Max.
 

Thread Starter

Ratisse

Joined Jul 11, 2020
6
Typically T.M. manuf. do not provide schematics, as they are proprietary usually.
If you have it hooked up and working with the original control, then the only hope is to do some reverse engineering and go from there to use the board on its own.
Max.
The manufacturer is one option. If that doesn't work out, I was planning on contacting a few repair shops I saw online that had refurbished that manufacturer's boards.

If all else fails, reverse engineering it is. One thought that came to mind is trying to tap in through the 8-pin connection.
 

Giomonte

Joined Jun 26, 2020
6
You can replace the upper display with a PWM signal generator, e.g.:
https://www.banggood.com/search/xy-kpwm.html?from=nav (or Amazon, Ebay, etc.)

Connect module to board:
1. Attach "Speed Control Signal" wire from 8-pin connector (see Detail "B") to "PWM".
2. Attach 1 power and 1 ground wire from from 6-pin connector (see Detail "A") to "+" and "-".
3. The "PWM gnd" can be left empty or grounded (works either way; if someone knows in what way or what conditions that gnd is needed, please chime in).
4. The board takes a broad range of PWM signals; but 200-400Hz gives the fullest range of RPM and duty% (I used 200Hz).

Eventually, you can connect the "Tach Feedback Signal" from the 8-pin connector to an LED RPM display module, e.g.:
https://www.banggood.com/search/4-digital-led-tachometer-rpm-speed-meter.html?from=nav
You can power it from another pair of "+" and "-" from the 6-pin connector.

Caution: When wiring the PWM module, do not accidentally swap the "+" and "-" wires; the module will die.

Attached is a service manual for that line of treadmills (more info than user manual).
 

Attachments

Thread Starter

Ratisse

Joined Jul 11, 2020
6
You can replace the upper display with a PWM signal generator, e.g.:
https://www.banggood.com/search/xy-kpwm.html?from=nav (or Amazon, Ebay, etc.)

Connect module to board:
1. Attach "Speed Control Signal" wire from 8-pin connector (see Detail "B") to "PWM".
2. Attach 1 power and 1 ground wire from from 6-pin connector (see Detail "A") to "+" and "-".
3. The "PWM gnd" can be left empty or grounded (works either way; if someone knows in what way or what conditions that gnd is needed, please chime in).
4. The board takes a broad range of PWM signals; but 200-400Hz gives the fullest range of RPM and duty% (I used 200Hz).

Eventually, you can connect the "Tach Feedback Signal" from the 8-pin connector to an LED RPM display module, e.g.:
https://www.banggood.com/search/4-digital-led-tachometer-rpm-speed-meter.html?from=nav
You can power it from another pair of "+" and "-" from the 6-pin connector.

Caution: When wiring the PWM module, do not accidentally swap the "+" and "-" wires; the module will die.

Attached is a service manual for that line of treadmills (more info than user manual).
You're a legend. Thank you.
 

DarthVolta

Joined Jan 27, 2015
477
Well what happens if you use the original control panel, and set lowest speed, and increase it up to max ?

How much different is that, to the speeds you want ?

If it's some nice linear voltage slope, that controls the speed slope of the motor, than it should be pretty straight forward to scale it to the slope you want, for the output speed vs input signal.

What is the output signal that controls the motor speed ? IDK motors much, but I guess control signals can be anything like a variable DC, to a PWM signal.
 

Thread Starter

Ratisse

Joined Jul 11, 2020
6
Well what happens if you use the original control panel, and set lowest speed, and increase it up to max ?

How much different is that, to the speeds you want ?

If it's some nice linear voltage slope, that controls the speed slope of the motor, than it should be pretty straight forward to scale it to the slope you want, for the output speed vs input signal.

What is the output signal that controls the motor speed ? IDK motors much, but I guess control signals can be anything like a variable DC, to a PWM signal.
The original control panel works. I used it initially for checking diagnostics to make sure there were no issues with the board and motor.

My issue with the control panel is it's not optimal size wise. It's roughly 26" x 7".

After the parts arrive, I'll be building a compact variable DC power supply using the main board.
 

MisterBill2

Joined Jan 23, 2018
6,359
The hesitation to reply was because of the size of what you are asking for and the major lack of information. Prior to post #7 there was no information about what it was that you had and so any instructions would have been pure guesses. And guesses are not what you need.
 

Giomonte

Joined Jun 26, 2020
6
4. The board takes a broad range of PWM signals; but 200-400Hz gives the fullest range of RPM and duty% (I used 200Hz).
Addendum:
A recent discovery: My test of PWM signal on duty% response was done running a motor (original 3hp model) without load. I don't know if loading would alter my results or even whether my reasoning has any merit.
However, I recently saw a True 500HRC treadmill (from which the board comes) running, and noticed that the PWM LED was blinking rather slowly: ~10Hz by my eye. During my earlier tests to "Find the Keys to the Controller" (TM), with the PWM signal set at 200Hz, the LED appeared solid ON; in fact it blinks at the rate of the PWM signal. All this to say that the factory PWM signal setting for this board (ME62T) appears to be ~10Hz.

If someone knows some engineering theory for selecting the PWM signal for a motor / motor controller / application combination, please chime in.
 
Top