# reaction time meter

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#### MrDEB

##### Well-Known Member
I am into pinewood derby drag racing. Have track with digital et readouts per lane.
Also in addition have a "christmas tree" starting system where by the perticipant can release his/her own car by pushing a NO push button.
If the participant releases their car before the green light then a red light comes on.
just like real professional drag racing.
BUT I want to add a reaction time display per lane (two lanes)
contemplating just an up counter circuit that starts counting when the last yellow light comes on until the participants car is released thus stopping the timmer for that lane.
found this timer on ebay but connecting to tree is ??
https://www.electro-tech-online.com/custompdfs/2009/02/09008.pdf
considered just triggering off the last yellow light when it shuts off (connect to the 4017 outputs.
any suggestions??
found several LCD 24charactor x 1 line displays ($1.85 each used) but more than I need want to display 3-4 digits per lane. #### Attachments • Capture2-23-2009-10.46.40 AM.jpg 192.7 KB · Views: 139 • Capture2-23-2009-10.46.50 AM.jpg 131.7 KB · Views: 110 #### MrDEB ##### Well-Known Member found a new 4 digit led display but? trying to figure the pinout the stopwatch timer circuit I located **broken link removed** looks fairly easy to construct. the led display$1.50 for a 4 digit display tsb7881
any other suggestions??

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• Capture2-23-2009-3.28.43 PM.jpg
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