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.
Posted by Phillip Torrone |
Sep 29, 2006 07:20 PM
Bicycles, DIY Projects, Instructables |
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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.
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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
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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.
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trebuchet03
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.
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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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