HOW TO – Make a versatile and low cost digital counter

Bikes Fun & Games
HOW TO – Make a versatile and low cost digital counter

Trebuchet03 writes – “This hack will transform a cheap easily sourced calculator into a versatile counting machine. It can be used as a cheap method to measure distance using a wheel, reed switch and magnet (think bike odometer).”Link.

Clever, it counts by adding +1.

10 thoughts on “HOW TO – Make a versatile and low cost digital counter

  1. Oracle1729 says:

    That’s a really cute idea.

    Would switch bounce be a problem though? Since you’re connecting directly to a button input, the debounce feature in the calculator would help a lot, but input sources like the reed switch or others could have much worse bounce.

  2. trebuchet03 says:

    I’ve yet to have any problems with the switch – emphasis on the yet. This particular switch was purposed as a door sensor for alarm systems – switches that are not used as frequently. So we’ve drastically increased how many cycles/day it experiences…

    My only complaint is the calculator programming (can’t complain too much for ~$1)… it has an auto-shutoff “feature.” I’m currently not aware of a way to disable that with any elegance :p

  3. ktekx says:

    That’s really clever idea, I just love the simplicity.

    At what rate of switching can the calculator handle per second?

    Debounce (if a problem) could be remedied w/ a low farad cap.

  4. hammerthumb says:

    If you find a calculator with memory you could put together a slow two transistor multivibrator from scrapped parts and connect it so it regularly switches the [M+] button. That might keep the calculator awake.

  5. trebuchet03 says:

    hammerthumb.. wow, you read my mind (at least for the method)…

    As for the speed — it depends on the calculator… but at a 20mph pace, I seemed to be getting accurate results on my bike (27″ wheel).

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