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Topic: Arduino-powered bike computer (Read 3 times) previous topic - next topic

DavidKunz

Okay, long story short: electronic-newbe programmer-guy is gonna build an Arduino-based bike computer.
I want to have at least speed, heart beat, cadance, GPS coordinates and time for outdoor rides, and RPM, cadance and heartbeat for indoor training on the Tacx, of course all nicely logged for further analysis.

So, my main problem is that I'm quite afraid of pushing the Arduino's (Uno R3, in my case) limits. I think I'll need at least a GPS-shield, a SD-card shield for the logging, two Hall Effect Sensors (wheel revolutions and cadance), a heart beat sensor and a LCD-display for the output (speed, heart beat etc).

The first problem I'll have to fix is getting to know if this is possible on one Arduino or not. Using two Arduino's is possible, but would complicate the things more then I like.

Can anyone here tell me how many shields and/or sensors an Arduino can handle, considering the fast-paced readings of the sensord on the wheel and cadance?

TMRh20

#1
Mar 09, 2013, 12:21 am Last Edit: Mar 09, 2013, 12:26 am by TMRh20 Reason: 1
Totally possible on one Arduino, and if speed is a concern, just make sure all of your modules support I2c or SPI, and it will handle it.

You can use interrupts for the hall-effect sensors, so the Arduino doesn't have to keep checking the state, and it will handle it easily enough. You woul have install jets on your bike before worry about overrunning its capabilities.

The amount of sensors is limited by what type of sensor etc, so is kind of impossible to give you a max number, but it can handle multiple I2C devices, so you could run the GPS, SD card and LCD all off I2C.


DavidKunz

Haha wow, good to hear.
I did a bit of research, and the internet is stuffed with half-finished projects like this. Got worried because it might be impossible to do on a Arduino, but lucky enough that's not the case.

Thanks!

So, an Arduino can handle a Hall Effect Sensor firing changes multiple times a second?

TMRh20

Yeah, it can handle counting many thousands of times per second, so handling inputs from sensors on a bike should be no problem, especially if you use interrupts, so it only does work when there is a change of state.


DavidKunz

Hmm. Makes me think, if an Hall Sensor only has state HIGH when the wheel-magnet passes it, it will be HIGH for a freaking short time. It will pass about five times a second (rough calculations after four beers, haha), but only trigger a small portion of that time. Is that long enough to be catched every single time?

Damn, the list of questions for this projects is longer then I thought. Love it!

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