Does anyone know the ins and outs on how these sensors work? Specifically the reed switch based units with a magnet on the crank and how their battery systems work?
The reason I ask is the company I work for builds automated machines and we have a need for a compact wireless sensor to monitor rotation. We couldnt find a industrial sensor small enough but being a cyclist I had the idea to use a cadence sensor. The battery life was a concern so we went and bought one and set up a test with a motor and the sensor and have had it running at 120rpm 24/7 for around 3 weeks now. We wrote a basic app on a PC to log the the signal and battery life. We are a little confused as the battery life the sensor reports seems to fluctuate a lot. It sometimes drops as low as 37% but then goes back to 100% later. Mostly it sits between 80% and 100%.
The sensor uses a standard CR2032 coin cell that isnt rechargeable. My theory is the sensor has a coil that generates a current each time the magnet passes and this charges a small internal battery. During use the sensor uses this battery and this is the battery level that is reported. The CR2023 battery is only there to power the sensor during sleep mode when not in use. Can anyone confirm this? The sensor we bought is a Giant 2 in one unit.
