Pushing Chest Strap Heart Rate To A Stock Exerciser Display

November 26, 2011 by Mike Szczys 3 Comments

This hack came out so well that [Levent] wishes he had tried it years ago. When exercising he wears a Polar heart rate monitor which sends data from a chest strap to his wristwatch. But his exercise bike also has a heart rate readout that depends on your hands touching metal contacts on the handlebars. He set out to see if he could patch the chest strap data into the exercise bike LCD display.

The first part of the hack is really simple. As we’ve seen several times before, you can buy a receiver module which grabs data from the chest strap. Now it was a matter of patching the data from this receiver into the Schwinn 213 recumbent exercise bike. [Levent] pulled out the PCB and located the small daughterboard that is responsible for the hand grip heart rate. With careful study he was able to identify the pinout. There are two data lines. One is responsible for the heart rate detected signal, the other pushes the actual heart rate data. On a hunch he hooked a signal generator up to the latter and discovered that all it takes is a square wave.

The rest is pretty straight forward. Check out the proof in his video after the break. Continue reading “Pushing Chest Strap Heart Rate To A Stock Exerciser Display” →

Fingertip Heart Rate Monitor

February 17, 2011 by Chris Nelson 12 Comments

[Embedded lab] has a nice tutorial on building your own heart rate monitor. The monitor works by shining infrared light into the fingertip and looking at the changes in the reflected infrared signal caused by a heartbeat. The IR detector produces a very small AC signal so a couple of op-amps are used to filter and amplify the signal. The output of the filter circuit is then read in by a PIC16F628A, which counts the beats and displays it on a seven segment display. This might be a good project to try if you’ve got your microcontrollers down and you are looking to learn some analog electronics. Its noted at the end that the two main problems with building a circuit like this are going to be cross talk and adjusting the filters. The infrared diode and receiver should be close to each other to allow maximum reflection but you also need to make sure that you don’t allow the emitter to shine directly into the detector because the reflected light will be drowned out by the bright emitter.

[via make]

The Quest To Build A Better Stairmaster

November 24, 2010 by Mike Szczys 22 Comments

[Eric Feldman] likes to use the Stairmaster in his exercise routine during the winter months. But apparently the exercisers that are designed for mere mortals don’t satisfy his need to climb stairs really, really, quickly. After mastering the upper speed limits of some top-of-the-line equipment he contacted the company asking if there was a way to unlock the software-imposed speed restriction. They laughed at him; a motivation that he used to build his own that is already five times faster. He calls it the Stairmonster, and after being tested at over 500 stairs per minute that name is quite fitting. It’s got a nice interface for choosing an exercise program and recording data from his routines. It uses an AT89C51RD2 along with a quadrature decoder and a heart rate monitor module that talks to a chest strap worn during each session. A 320×240 touchscreen gives feedback on the routine, which is altered to achieve targeted heat rates for optimum results. Nice job [Eric]!