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Trying to build a timer switch

Steven L Coulombe

Feb 11, 2016
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Feb 11, 2016
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I'm looking to build a timer for my science class that needs to be quite accurate. I'd like it to start as an object is released, and stopped again once it stops. I want to be able to calculate average speed. I have no idea what components I would need to accomplish this. Buying one would be easier, but I don't even know what to search for.
 

KMoffett

Jan 21, 2009
723
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Jan 21, 2009
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"If you are trying to measure falling objects you will find they all fall at the same rate."

Only in a vacuum! ;)

Ken
 

KMoffett

Jan 21, 2009
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Jan 21, 2009
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Steven,

If you want to buy one, Google: photogate
There are commercial ones like: http://www.novatech-usa.com/Products/Mechanics-Educational/DTPHG1?gclid=CIC4q_HW8MoCFdcYgQod4nAOoQ
I've used cheap stopwatches to time periods. Used LEDs or laser pointers and a photo transistors to detect the start and stop events. Photo transistor drives a MOSFET. The is MOSFET placed across the stopwatch's start-start switch contacts. How accurate do you need the time to be? I think stopwatches are good to 100th of a second. But this requires some electronics skill.

Ken
 
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