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dhiltonp / marco-gps

GPS Bike Computer
MIT License
5 stars 1 forks source link

Interface with bike speed sensor #7

Open dhiltonp opened 8 years ago

dhiltonp commented 8 years ago

Figure out whatever is necessary to not fry the board (resistors to restrict voltage, maybe tune some capacitors). Also, consider how to attach/detach. Do I have room for spring clips? Or should I use mini-deans?

dhiltonp commented 8 years ago

http://www.atmel.com/images/doc2508.pdf - 2x1Mohm resistors will show close to the full voltage, but the internal diodes will clamp the value.

Experimentally, I had issues with that exact setup. My wires generated enough noise to register values. I replaced the 1M resistors with 330k and added 3rd 330k resistor as a pull-down.

When I tested with a 100k resistor, about .2 mA of current were being generated; the on-board clamping diodes are supposed to be rated for 1mA.

ESD notes for non-AVR chips are not to be found. This is cool, though.