Recently I came across an article in a popular german computer journal about the combination of a statinary bike and a Arduino (http://www.heise.de/make/meldung/Fuer-40-Dollar-mit-dem-eigenen-Rad-in-die-Virtual-Reality-3097272.html).
I wanted to go a step further and not only measure the rotations, but also the my performance in terms of power. The plan is to use this information to control the playback speed of videos that I watch while exercising.
First I disassembled the display and control unit of the
| bicycle ergometer: |
The main goal is to find out how the computer derives the quantities in the display (rpm, distance, power, speed,...) from the signals on these wires.
After quick and dirty soldering some thin wires to the connection points on the circuit board
all the hardware aspects of the project were already done.
After connecting the wires to the analog inputs of my LabJack U3-HV (https://labjack.com/products/u3) it was time to record data.
After some trial and error I found the following:
1. the brown and red wire have a constant 12V, so this is probably the power supply
2. the differential voltage of the yellow and green wire gives 5V pulses, the time distance of these pulses encodes the rotation speed of the pedals
3. the differential voltage of the black and orange wires controls the power of the eddy current brake.
The above plot of the differential voltages shows a short test with the lowest brake setting and a constant rotation speed of the pedals.
The rotations speed is actually the only information that the ergometer computer gets, the setting of the brake is output.
The integration of this measurements into the video playback and detailed training analysis will be done later.
