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555 Timer

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energizerD

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I need to build a timer that activates a relay if the trigger is held
on for 10 seconds. (less then 10 seconds will not activate the relay)

I am sure a 555 or 556 timer circuit can be modified to acomplish this....

Does anyone know of a schamatic diagram that will do this?

Mark
 
Time for Timer

My first instinct would be to have a 555 astable-configured at 10 seconds per pulse. Insert a momentary button switch on the power lead. Output starts positive then after 10 seconds pulses negative for a time period that you can adjust also. The only thing is: it will go back positive and pulse again after 10 seconds if you keep holding the button, and so on.
I like this better: If you want it to start negative and pulse positive, take its output (Pin 3) and go into Pin2 on another 555 chip that is monostable-configured. Its Pin3 output will pulse positive. (Or use one 556 to do both. Output Pin5 to input Pin8.)
Here's some good ol' Forrest Mims pages with schematics and time tables from the ol' Radio Shack books they used to publish...

I'd love to hear back how it goes AND what your application is for this.
 

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I need to build a timer that activates a relay if the trigger is held
on for 10 seconds. (less then 10 seconds will not activate the relay)

I am sure a 555 or 556 timer circuit can be modified to acomplish this....

Does anyone know of a schamatic diagram that will do this?

Mark

What happens after the 10 sec period?

If the input lasts, say 10.01 sec, does that mean the relay is on for 0.01 sec?

If the input lasts, say 11 sec, does that mean the relay is on for 1 sec?

How long do you want the relay on if the input lasts, say, 100 sec
 
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