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STEPHAN
New Member
USA
2 Posts |
 Posted - Jan 17 2010 : 11:03:11 PM
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Hi,
I need to build a little alarm circuit that starts beeping if a door is open for more than a set time, for example 30 seconds.
This needs to be build into a save.
So, I installed a little switch.
Switch opens, circuit waits for 30 seconds, little beeper goes off. Can stay on, until door gets closed.
Just to clarify, this is not an official alarm (that’s a different system) and just a reminder to close the door fully.
I believe this should be very simple, but I don't know were to start. I am German and now live in the US, but have no idea were to get help.
I would appreciate any hint !
Stephan
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ahonda55
Apprentice
Egypt
57 Posts |
Posted - Jan 26 2010 : 11:11:46 AM
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I made such circuit for the refregirator door, monostable timer circuit using 555 IC, the switch is powering the whole circuit with 12v, then a transistor or a relay to switch what you need on or off.
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Aaron Cake
Administrator
Canada
6718 Posts |
Posted - Jan 30 2010 : 10:49:47 AM
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| Yep, the 555 timer is where you want to start. Check the datasheet or just Google for "555 monostable" and you will find plenty of circuits. |
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Door open Alarm
