This is a common monitor for a NordicTrack Skier. These were made in the 1990s. Electrolytic capacitors eventually dry out and items using them no longer work. Contacts on input buttons of the type used in these can also become weak or fail completely. Or, people leave batteries in these units too long and corrosion damages battery contacts, as well as circuit traces. And, components change in value.* This one still works fine, but I wondered about a simple backup replacement that would tell me my ground speed and the duration of my workout in minutes. I use ground speed to know what level of effort I am using so I can compare it to what I usually do. That and the duration of my workout in minutes are the two things I find most necessary.
*A few years ago our church security system began to give false alarms. The police would allow a minimum number of alerts in a month, but more than that would result in a hefty charge for each false alarm. We even thought we might have a rodent in the building and set a rat trap, but the bait was never missing. A check with the alarm company representative resulted in a new alarm system. After 25 years the circuit board in our system had become unstable and was giving false alarms.
Step 1: Schwinn Cyclometer
In 2008 Sailor Bob published an Instructable about how to program a common Schwinn cyclometer for use as a cadence meter so a bicyclist knows how many revolutions the pedals are spinning. I finally remembered that Instructable and wondered if I could program the same Schwinn cyclometer to replace a NordicTrack computer.
In the photo the Schwinn cyclometer is mounted to the handhold bar.
- Schwinn Cyclometer (I got mine at Wal-Mart for about $12 US. In just a few years the price has risen to almost double that. Any bicycle cyclometer that uses a reed switch and magnet for a sensor, and sets the wheel size with four digits representing the wheel circumference in millimeters could be substituted.)
- Electrical tape
- 1/8 inch mono male audio connector (1/8" stereo will also work. See the next step.)
- Screwdriver for mounting (Some Schwinn speedometers come without a screw-tightened collar. Use small cable ties, instead.)
- Soldering iron and solder
- Side cutters
Step 2: The Connection
The sensor on a NordicTrack Ski Machine is a magnet mounted in a flywheel and a reed switch very near to where the magnet passes as the flywheel turns. The same type of sensor is used on the Schwinn cyclometer. Rather than use the reed switch already on the cyclometer, I cut the wire and soldered on a 1/8 inch mono audio connector, like the one shown in the first photo. The second photo shows the reed switch used as a pickup sensor on the fork of a bicycle.
I did not use the pickup sensor reed switch already on the cyclometer because the wire was not long enough to reach all of the way down to the ski machine's flywheel. Instead, I added a 1/8 inch mono* male audio plug and plugged into the computer sensor jack on the ski machine's upright post. See the third photo. Because this was a test rather than a finished product, I have not yet insulated my solder connections.
*A stereo plug may be easier to find since Radio Shack stores are less available in the last couple of years, particularly if it were taken from a pair of earbuds that no longer work. If you are using a stereo plug, use an electrical tester to identify leads and connect for the tip and for the second band behind the tip, not the band immediately behind the tip. That will work just fine, unless there is a break in the wire already connected to your plug. (Earlier I had erroneously written that the band behind the tip should be used, but discovered that is incorrect and have changed the text accordingly.)
Step 3: Calibration
I experimented with how to set the Schwinn cyclometer to give a reading as close as possible to the readings I get from the NordicTrack computer. The display on the NordicTrack computer (second photo) is set to show speed in miles per hour.
See the first photo. The Schwinn cyclometer is showing a speed of 3.7 miles per hour. I switched connections back and forth between the Schwinn cyclometer and the NordicTrack computer in order to compare readings and efforts for the sake of reasonably accurate calibration.See this link on the mechanics of programming the Schwinn cyclometer. A copy of what you find there is included with your cyclometer when you buy one, but people do lose those instructions in time.
I found I need to set the Schwinn cyclometer for a wheel size of 0470 and then select miles per hour to get the readings I would expect on the NordicTrack computer. The wheel size of 0470 would be the same if you chose to have the final reading in kilometers per hour.
Step 4: Other Data
The Schwinn cyclometer does not give some of the data available on the NordicTrack computer, like pulse and calories burned. It can give distance traveled and the time duration of the exercise session. (See the small numbers across the bottom of the Schwinn display. According to the reading, I have been exercising for 2 minutes and 56 seconds at the time this photo was taken. The time duration of the last workout session is held in memory and should be deleted before the start of a new session. See the Schwinn instruction sheet linked in the last step on how to bring up the duration of the workout and how to zero out the reading from the previous session.)
As regards pulse, here is a work-around. I used a heart rate monitor some a few years ago when I was doing a lot of bicycling. A very good range in which to exercise for weight loss is 75% to 80% of one's theoretical maximum heart rate. I found I am in that range when I am on the threshold of switching from breathing through my nose to a need to breathe through my mouth. Although an oversimplification, one's theoretical maximum heart rate is the constant 220 minus one's age in years.
At the very best, calories burned per hour as reported by the NordicTrack computer is only a reasonable guess. The amount of effort expended is also a factor. At this site, you find this information: The Nordic Track ski machine can help you to burn calories and get in shape. According to Calorie Lab, a 150-pound person on a Nordic Track Ski Machine will burn 415 calories per hour for light effort, 496 calories per hour for moderate effort and 571 calories per hour for hard effort. If you weigh more, calorie expenditure will be somewhat greater. If you seek out more information like this, you may not find information related to a ski machine, but try searching for cross-country skiing.
If you are familiar with Dr. Kenneth H. Cooper's aerobics program, you can get a table of exercise point values for cross-country skiing here. (Scroll to page 18 of 21.) A reasonably fit person gets a minimum of 30 points per week. 20 minutes of cross-country skiing is worth 6 points. 30 minutes is worth 9 points. Some of Cooper's charts will mention a ski machine, but this fairly comprehensive chart does not, so cross-country skiing is the closest applicable category. Unfortunately, this chart also does not distinguish for different levels of effort.
If you have a NordicTrack monitor and need to replace it or if you do not have a monitor and want one, you can use newer technology in a recently manufactured device for very little money.