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Need help with 555 IC timer circuit for a race timer

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groundhangers

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Im currently trying to turn a Standard stopwatch into a race timer for slalom skateboards.
The main problem faced is that a stopwatch uses the same button for start and finnish.
The switch that i am using is a tape switch which goes on the ground for you to run over
activating the stopwatch, the problem is when you run over it with your front wheels the
timer starts but when you run over it with your back wheels the timer stops.

What i need is a simple 555 IC timer circuit so when i run over it with my front wheels it
triggers the switch but when i run over the tapeswitch with my back wheels the switch
is ignored for a period of 1-5 seconds before retriggering again.
I have looked through the net extenively and havent found anything suitable. I can build
from a diagram but unfortunately i dont understand electronics that well to make a diagram.

Any help would be great.
Thanks,
Greg
 

unkarc

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small project on ic 555

Hi,

Basically you need to use the 555 timer in MONOSTABLE mode. See one of the many links on that circuit of this link and scroll down to Monostable circuits

https://www.doctronics.co.uk/555.htm

Make sure to read and understand the section under More about triggering
to avoid any trigger possibilies coming from the back (rear) wheels.

unkarc
 

hotwaterwizard

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Re: 555 ic timer curcuit

Here is a simple Circuit I use for such things use a smaller capacitor for shorter times.
 

groundhangers

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Re: 555 ic timer curcuit

I put built the monostable circuit, but the problem with it is to reset the trigger, you have to turn the power off and back on again to activate the trigger again.

Ill give your one a go Hotwaterwiz and ill post up a result when im done.
Thanks,
Greg
 

groundhangers

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Re: 555 ic timer curcuit

Thanks for the curcuit hotwaterwizard it works exactly how i wanted it to. Damn Champion!:D
 

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