Controlling treadmill from external panel

[Menticol]

Hello everyone!

The objective of my project is to control the speed and inclination of a treadmill using an external micro controller, getting rid of the original control panel.

After watching a YouTube video where someone injected PWM signals directly into the board (of a similar make and model), I assumed that my OEM user panel worked similarly.

To investigate further, I created a small breakout board and started probing the connections with an oscilloscope.

To my dismay, what I observed on the oscilloscope made no sense. I identified two ground connections (G), a +3V line (S), and an +9V line (V). But on the connection labeled P, where I expected to see the control signal, there was indeed a signal, but with a frequency between 16 kHz and 20 kHz, that did not vary with the treadmill motor speed.

Any suggestions regarding how to interpret this carrier / proprietary signal will be very appreciated.

2025-01-15 EDIT:

Yes, ChatGpt is very useful, but its opinions must be taken with a grain of salt, or in this case, not taken at all.

First, I as convinced this was some kind of "proprietary protocol", when it is not. The unit is controlled by varying the duty cycle of a square wave. Simply changing the duty cycle provides full motor control.

Second, take all measurements where the control signal is generated (near the user control panel) and not near the motor controller board. The 20 kHz was just noise!!!

Best luck on your project, and avoid making my same newbie mistakes!

 

[MaxHeadRoom78]

It looks very similar to the MC2100 boards, these have a an 8 pin input socket for the console hook up and does use a 20Hz PWM signal to bench run the belt motor.
The board in your pic does not quite look like the same series, what is the part No. on it?

 

[Menticol]

It looks very similar to the MC2100 boards, these have a an 8 pin input socket for the console hook up and does use a 20Hz PWM signal to bench run the belt motor.
The board in your pic does not quite look like the same series, what is the part No. on it?

Yes sir, you are absolutely correct: 20 Hz it is!

For anyone tinkering in a similar project, inclination is ordered via a short pulse on either the yellow (D) or orange (U) cables. Current inclination is reported back to the user board trough the purple (S): if upwards end of travel is reached (S) will go down, if downwards end of travel is reached - parallel to the floor (S) will go high.

Ridiculously simple! But my bad oscilloscope measurements and blind reliance on AI created a completely imaginary problem