429Views7Replies

Author Options:

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!

Discussions

0
None
freethetech

7 years ago

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.

0
None
pizza1993

7 years ago

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)

0
None
Goodhart

7 years ago

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.

0
None
caitlinsdad

7 years ago

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

0
None
pizza1993caitlinsdad

Reply 7 years ago

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?

0
None
caitlinsdadpizza1993

Reply 7 years ago

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