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Laser alarm circuit Answered


I am searching for a circuit which can drive a siren circuit like this and can be activated by a laser pointer.I have tried a lot of these circuits but all had the same problem:The siren sounds only for a few seconds(As long as theinterruptionof the laser beam...)

Thank you in advance!

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freethetech (author)2011-07-22

I would just create a latch using a relay - http://www.youtube.com/watch?v=cPjRhtuSxz0

If you wanted to take it a step further, I'm sure you'd have no problem creating a logic gate so that if the latch output is high and it is activated by the laser it turns low, and vise-versa.

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pizza1993 (author)2011-07-22

Thank you for your advice!What i really need is a time circuit that can be turned on with a instant high voltage(5volts+) and the output voltage remains for a calculated time period,but cant be turned on by a low voltage(0.5volts)

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Goodhart (author)2011-07-22

What you then need is, according to your description above, a "latching circuit" OR just a latching relay. It goes on, and stays on, until you turn it off, or until some other signal turns it off, however you set it.

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caitlinsdad (author)2011-07-21

Then you need the photorelay to trigger some kind of timing circuit .

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pizza1993 (author)caitlinsdad2011-07-21

A trigger is a quick changing in voltage,isn't it?Can i power up a timing circuit by a transition from 0.5volt to 5volt or the timing circuit's input voltage must be a transition from 0volt to +(...)volt?

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caitlinsdad (author)pizza19932011-07-22

look on your circuit site for that burglar alarm circuit. It should help you out. Good luck.

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