Fix Your NordicTrack Exercise Bike

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Introduction: Fix Your NordicTrack Exercise Bike

About: Software Developer, like to work with electronics, embedded systems, robots etc.

The other night I was riding my Nordictrack exercise 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.

Step 1: AC Adapter

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

Step 2: The Pedal Assembly

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

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.

Step 3: Rear Weighted Wheel

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

In a minute we will look at how the motor and wheel works.

Step 4: Motor Assembly

Lets take a closer look at the motor assembly.

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.

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:

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.

I tried it 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.

Step 5: The Display/Controller

It is 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.

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 exercise 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.

Step 6: The Fix

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:

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:

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.

Enjoy

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We have a be nice policy.
Please be positive and constructive.

Tips

2 Questions

Do you think a DPDT Car window switch would work to replace both the momentary and DPDT switches for this? Should be for step 6.

0

Hi, only if the switch has a momentary push function, The step that refers to wiring in the switch

I have a NordicTrack GX 4.0 recumbent bike. Everything works great except the backlit screen has started flickering. I’ve taken the panel apart and the board looks very much like the one in the picture you posted. Do you have any thoughts on what part of that thing I would attack to try to remedy the flickering? Thanks so much.
Mike

13 Comments

Thank you for your post. I'd followed your instruction until step #5. At this step, I'd found this 8-pin IC smoked out but I could not see the part number anymore. Could you help me to identify what IC is this?

Thanks,

David

IMG_0646.jpg
3 replies

Hi, My board is long gone. The manufactures purposely wipe the chips of any identification so you cannot replace them. Sorry.

Joe

Thank you for your reply. I guess my only option left is following the rest of your fix then.

Hi

I need some help with my NordicTrack E4.1 elliptical bike. I don't know where to post in on this website so I thought that being so close to this topic, this is the place :)

My tension motor assembly is broken. Not the motor per say but a tiny plastic wheel. While I can buy the whole assembly for about $80, I would like to replace only the broken part.

I've attached a few pictures to help you understand the issue.

Also, I would need some guidance how to reinstall the tension motor assembly. My understanding is that I should put the tension to maximum (from console), install the assembly, plug in the wires and that's it. My question on this part is: do the break pads (which I think are made out of heavy duty magnets) have to be in contact with the metal fly wheel or just very close? It was the first time when I put the tension to maximum when it broke and I guess the magnets got in contact with the wheel and it was too much for the tension motor assembly. But this is just a thought and I wish to avoid fixing it and then braking it again.

Any advice is highly appreciated.

Cheers,

John

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Yes, your are correct, a momentary press on the switch would increase the tension. Yes it does look like your board is faulty. Use the wire diagram I posted then you can run the adjuster in or out to tighten or loosen the adjuster. Tension is totally arbitrary, based on how long you hold the switch.

Great post, thanks. I have a couple of questions though. My elliptical machine does move the resistance motor, but if I start at level 1 and then change it to another level, it would go all the way to the maximum. I don't know what then is busted, if it is the motor or the board. Now, if I do the hack, and I understood correctly, it will raise the next resistance level when the momentary switch is pressed, right? And lastly, why not use a potentiometer scaled 1 to 10 for example? It is because the resistance motor already has its potentiometer?

Sorry if these questions are so elementary, but I do not do much electronics.

Thanks for answering.

2 replies

Hi, more than likely the board, but to test you can disconnect the the motor from the wire harness and test by taking your ac to dc adapter and trying to connect the wires to the ac adapter to see if the motor turns. If the motor moves the adjuster then your board is at fault. Then your best best is to do the conversion that I posted.

Thanks

Joe

It does move. I hooked a voltmeter to the yellow and blue terminals at the motor and hit the - and + sign on the console. The console also has five buttons for pre-set resistances (1-4-8-12-16). If I hit 1, then it goes all the way to the minimum resistance level, so that works, then if I press 4, then it shows 5V for a while and it seems to me that goes farther than level 4. If I hit 8 then it does not do anything, then, I press 12 goes to the max and make some sort of adjustment. Pressing 16 shows a slight change in voltage but very quickly though. I could press 8 and then use the - sign and it would adjust, but that is not always the case.

Anyhow, the conclusion is that if the motor works, then the board is faulty. I thought that maybe the resistance was bad even when applying voltage to it would move. So, how does it work? Why is it that it has also the red, black and white leads? I checked and black and red always has 3V. Red and white also show 3V, but when the resistance buttons are pressed, then blue and yellow show 5V.

So the idea of having the momentary button is to indicate the amount of time you want the voltage to run through it, right? So, in a sense, the step resistance would be highly arbitrary, correct? Therefore, leaving it pressed would reach to the max, while pushing it for a second or so, would be similar as going one step above if the DPDT switch is up, or a lower resitance level if it is down.

Thanks very much for your time and reply. I was searching for a long time on the net and your post was what I was looking for.

A friend at Instructables does a lot of work with NordicTrack ski machines. I have tried to help him with a couple of things. He sent a digital controller to me to look at. In addition to providing several LCD displays on various exercise metrics, it has buttons that are supposed to drive a small motor to increase or decrease belt tension. I can connect DC power directly to the motor and it operates the screw mechanism for adding or removing belt tension on the flywheel. But, there is a transistorized motor driver circuit for powering this motor and for reversing its direction. The circuitry is 1990 vintage. I know the power adapter and connection harnesses feed current to the circuit board. I have been trying to check a few components as best I can in circuit with a multi-meter. There are four germanium diodes encased in glass that I would like to check disconnected from the circuit. In the end, we may need to do a work-around like you did.

2 replies

Hey Phil, good to hear from you. If it is vintage electronics you just may have better luck than I had. Discrete components are much easier to trouble shoot and replace than an all chip solution. Yes, the motor circuit is pretty much just a DC motor and I am sure that the controller board uses PWM to control the motor in short bursts. Depending on how the diodes are in the circuit you may not have to remove them, Just check each diode with you multimeter set on diode check and reverse the polarity. You should get a reading in one direction, but no reading the other direction. If you have an in circuit ESR meter (such as the Peak ESR meter) you should be able to check the caps in circuit as well. as long they are not in parallel.
Anyway good luck with your probing.

Joe

Thanks, Joe. My meter has a diode check function, which is handy so I do not push too much current through a diode and ruin it. The reading in both directions is nearly identical, which is not a good sign unless something provides a back door path. I have another meter that does have a capacitor check function, but I would need to remove the capacitors from the circuit.
Removing the diodes is a little tricky. The leads are short and there is little room for a heat sink. Also, there are traces on both sides of the circuit board. I tried to remove one lead and tore the upper trace away from the circuit board, but did not break it.

Looks like a great fix for your exercise bike. Thanks!