I am interested to build a bike but I would also like to have free software/hardware. How can I build a cyclometer with open-source software? Would it be possible to find reflashable hardware or open schematics?

  • @Neil Fein: are you saying that cyclometer has nothing to do with bicycles? lol... start a project, we live in it. We like to have fun with bicycles, why are you so intolerant about fun? I think most of us, repliers and me, won't give a damn to time-limits and such things in so-called projects, let us work. If you cannot understand, look there are many other people who understand, read the replies. Very cool!
    – user652
    Commented Feb 18, 2011 at 1:59
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    Cyclometers are clearly on-topic. This question is simply unclear as it is currently written, and I want to understand it. Stack Exchange, the company that runs these boards, is very clear about what they are to be used for, and that's asking and answering questions. I'm not trying to ruin anybody's fun. However, questions have to be clearly written or at least understandable, and this one, in my opinion, is not yet there. I'm doing my best to help you, not hider you. Commented Feb 18, 2011 at 2:06
  • @Neil Fein: What do you mean? Yes I am asking here, other people are answering and they clearly understand -- notice there is a clearly-defined understandable question about bicycles which already has many understandable answers. If you are going to remove this question, please, remove also [1], [2] and many other software-hardware related questions. [1] bicycles.stackexchange.com/questions/1689/… [2] bicycles.stackexchange.com/questions/725/…
    – user652
    Commented Feb 18, 2011 at 2:25
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    I'm voting to close this question as off-topic because it's an extremely broad question that's primarily about electronics, rather than cycling. (Rule of thumb test: would it be easier to explain the necessary cycling information to an electronics expert or to explain the necessary electronics to a cyclist? Clearly the former and by a very, very long way.) Commented May 29, 2018 at 15:45
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    I'm voting to close this question as off-topic because it belongs on electronics.stackexchange.com
    – Criggie
    Commented May 30, 2018 at 7:28

3 Answers 3


Easiest platform is probably arduino - nearest bike thing I can find is this

  • +1 cool so I don't need to buy a closed code cyclometer, had actually some arduinos around.
    – user652
    Commented Feb 16, 2011 at 23:44
  • At the speeds things happen on bicycles it's very easy to just count the inputs from a magnet+switch with an interrupt. Hardest part is probably a suitable cheap display
    – mgb
    Commented Feb 17, 2011 at 0:02
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    @wdypdx22: I have used this beast [1]. Very small and now planning an automatic chain lubricating thing but unsure of your requirements. Check the specs. [1] pjrc.com/teensy
    – user652
    Commented Feb 17, 2011 at 0:57
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    There are surface mount nano versions arduino.cc/en/Guide/ArduinoNano, or there is this arduino.cc/en/Main/ArduinoBoardLilyPad
    – mgb
    Commented Feb 17, 2011 at 2:42
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    @hhh all the arduino variants are free and open source, they also use the same very simple IDE and language. You can also get arduino clone boards from local makers, some smaller and cheaper.
    – mgb
    Commented Feb 18, 2011 at 6:10

The most detailed account/details I've come across for building your own bike computer is here on PIClist.

Those pages contain detailed instructions for building a bike computer using a PIC microcontroller linked to a Hall Effect Sensor (it detects the magnet attached to a spoke as the wheel spins). In addition to the build details it also features a detailed discussion of the design process which the creator undertook whilst creating the computer.


I tried to get real time ANT sensor data from a Garmin watch to a PC. But this is difficult. BLE is easier. The following bike computer is very basic, but can be modified by the user:

Pyloton: CircuitPython Cycling Computer. Open Source cycling computer that displays heart rate, speed, cadence, and song playback info.