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Analog Fix for Nordic Track Exercise Bike

The other night I was riding my NordicTrack Bike and all of a sudden the display quit and the tension on the peddles went slack. The wife has been on me for quite some time to start exercising as I sit behind the computer the major part of the day.

So I decided to take the thing apart and see If I could trouble-shoot what was causing the control and display not to function.

I will get into showing you the tear down shots later. Right off of the bat I thought, cool if the controller is shot I could replace it with a micro-controller solution. This would be a cool project.

But then reality set in and I realized that this project would take some time and I am currently working on some other micro-controller projects.

So back to tearing the thing down and see if I could fix the darn thing.

The display has two sets of connectors coming out of it. I had no clue to what they were connected to. So I decided I had to tear the plastic off the bike and take a look at how the bike was wired.

Grabbed the multimeter and some tools. Stripped the bike down to the frame and started taking a peek how this bike works.

Lets take a look at the key sections of the bike.

power

We will start at the front of the bike. Notice the ac adapter, 12 volts, 1 amp DC adapter.

A bit further back, The peddle assembly, Notice the Halls Effect sensor and the magnet mounted to the peddle assembly.

Halls

The Hall Effect sensor is used to count the number of wheel rotations and calculate things like speed and distance traveled. Along with the hall effect sensor and the weighted wheel potentiometer, calories burned can be calculated.

At the rear is the business end of the exercise bike, there is a weighted wheel with a tension adjuster and a motor.

Here are some pics:

LeftWheel

wheel

That is it not a lot in the sensor and mechanical portion of the exercise bike.

Lets take a closer look at the motor assembly.

Motor1

On the motor we have a lever and a gear wheel no unlike a RC servo motor. So this motor my be controlled like an RC servo motor? maybe lets troubleshoot some more.

motor3

So we flip the motor over and notice how the motor is wired:
The motor has two wires connected, a yellow wire and a blue wire, no this motor is not an RC servo, it is just a DC motor. Also on the motor control casing there is a label.

On the label it indicates “6V tension motor P/N 241949″ I did some web searching and found that many exercise bike use this same motor. But I could not find any specifications on the motor. Just a few posts where other people have had some issues and one article on a vague description on how to test the motor by applying some current to the motor to see if the motor gear turned or not.

I flipped the motor to the other side and had a look:

motor2

Interesting, There is a 5000 ohm potentiometer on attached to the gear of the motor.

This would mean that when the motor is adjusted to increase the tension of the skid closer to the motor the resistance would increase and likewise when the motor reduced the tension against the wheel the resistance would decrease. At least that is what I guessed. Lets do some testing.

So I installed the motor back into the exercise bike and put some batteries together for some testing.

I applied some voltage to the yellow and blue wires and sure enough the motor started to turn to move the skid closer to the wheel. Just like a servo though there is a stop and you have to be careful not to keep the motor running against the stop.

So then the question is if I reversed the wiring on the motor would the motor reverse direction and turn pull the skip away from the wheel. Tired is and sure enough the motor changed direction and moved the skid away from the wheel.

I then attached my ohm meter to two of the terminals of the potentiometer and ran the motor forward and backward and the ohm meter read from 0 – 477 K ohms.

The potentiometer readings along with the hall effect sensor are used to calculate calories burned, speed and distance traveled.

I traced the wires back from all connections to the 10 pin wire connector and found out which wires applied power to the display and controller. I also noted where all of the wires from the potentiometer and halls effects sensor came into the wire harness.

It was time to take a look at the controller/display.

I removed the connectors and display unit from the exercise bike and took it to my work bench.

Display

I opened up the display/control unit and took a peek inside, not a good sign, other than a few capacitors there were no discrete parts, just a bunch of chips. So I disconnected the keypad and speakers and the iphone dock connectors and applied power to the unit. Instant current overload on the adjustable power supply. I tried to check a few connections but not much else could be tested. It appears to be a chip issue. There were no burn marks on the pcb traces. So it looked like the controller was fried.

I looked on line and a new controller was over $300.00. No freaking way was I going to pay that much for a replacement controller.

So I did some thinking and came up with a quick and dirty way to get the excerise bike working for around $15.00.

Really all I needed was a way to increase and decrease the wheel tension on the exercise bike. I really do not need the fancy data that comes off the bike for the time being. I could get the bike working and then when I had some time I could come up with a replacement controller using an inexpensive micro-controller solution with a LCD display.

Did a bit of web searching and drew up a wiring diagram, after a quick trip to radio shack I started to put together a workable solution.

Here is the wiring diagram I came up with:

Analog Switch

I picked up a DPDT switch, a DC adapter voltage connector and a momentary push button and a project case that I had laying around on my desk and some wiring.

After wiring up the new controller box I mounted the box to the exercise bike and connected the yellow and blue wires to the new control box:

Control

Connector

Notice I connected the output leads to the wire connector using some female jumper connectors. That way when I come up with a micro-controller solution it will be an easy fix to use the existing wire connector.

If you decide to wire up one of you own, you may have to swap the yellow and blue wires in order to have the DPDT switch increase the tension when the switch is pressed in the forward position and pressed rearward to decrease the tension.

There you have it, a working quick and dirty exercise controller.

Now I can keep my wife off of my back and get back to my other micro-controller projects.

 

Here is a YouTube Video

Enjoy

6 thoughts on “Analog Fix for Nordic Track Exercise Bike

  1. Joe….my nordic trac stationary bike power adapter has three wires coming from it. Red, black, and grey. The black and grey both seem to be negatives. On this model, when the pedals are turned, the display turns on. There is no on/off switch. The power adapter was damaged and now the unit won’t ‘turn on’. I have continuity on the red and black wires but not the grey. The power supply is ‘good’. What other troubleshooting might I do to narrow down the problem? Thanks in advance for any imput.

    1. Hello Mark, I saw the same thing on my bike, I followed the gray wire and it goes up to the wire connector on the controller board, so it may be a ground for the controller board. You say your power adapter is bad but then say the power supply is good. Could you explain more, I am not sure if you mean your ac adapter is bad or not. Did you try another ac adapter.

      Thanks

      Joe

      1. The PS is good…12.1v. The power plug (female) on the bike is what broke. I jumpered from the PS (male end) to the terminals on the back side of the female power adapter/plug but the display/panel still would not power up. I may have to go the route that you did to adjust the tension. There’s no way tha I’d pay what they ask for replacement parts and shipping. At first I thought that it was that 10 inch wire harness from the female power adapter to the wire harness. Nordic Trac wanted $21.00 for the wire and $14.00 for shipping. Are they out of their minds? Thanks for your help and expertise!

        1. Yes, Sorry, looks like your controller might be fried as well. Yes, I refuse to pay that kind of money for replacement parts. Especially when the quality of the electronics is bad from the start. Good luck, I am still riding my bike with the manual adjustment and it works great.

          Joe

  2. Hi Joe,
    Thanks for publishing your fix!
    My Nordic Track bike is a recumbent, but uses same basic electronics. In my case the tension motor just seemed the problem, because it turned, but it’s cheap plastic gears were noisy and the thing jittered a lot when I hooked it up directly. I was sure I was getting some voltage readings coming from the console board, so figured it an easy fix.. When I found the normally >$70 motor on E-bay for only around $50, I jumped on it. Now that I got it all hooked up of course the thing turns smoothly when I apply power to it directly, but the console just doesn’t seem to send it any juice when I change the level either manually or via a program. Going to fiddle with it some more, but if I can’t make it work I will be applying your fix here soon :)

    In my case the console LCD works fine, the amplifier/speakers work fine, the hall effect sensor seems fine as I get a speed reading, just can seem to get that tension motor to do its thing. I’m sort of a Raspberry Pi fan and am thinking of making this a little project to see if it I can make my own programs to drive the motor, calc my speed and calorie output, etc. If I get anything going, I’ll let you know.

    Thanks again!

    Jon

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