How to make a home security electrical circuit.?
Monday, September 6th, 2010 at
8:21 pm
Hi, i’m trying to figure how to make a home security circuit. I can’t figure how to make a buzzer go off if a door/window is opened. Am i right in thinking i’m going to need a parallel circuit with with 2 resistors with a higher resistor above the door (higher resistor meaning with more resistance) and a lower resistor on the door for when the door’s closed. Thanks
Tagged with: home security • how to make a buzzer • parallel circuit • resistance • resistor • resistors
Filed under: CCTV DVR System
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Depends on how complex you want to get. The easy way is with magnetic switches. The switch is next to the magnet when the door or window is closed and in the open position. When the magnet is moved away from the switch because the door or window is opened, the switch closes and the buzzer sounds off. Each switch would be on it’s own parallel circuit.
For a little better security, wire the switch so it is closed when the door or window is closed. The switch opens when the door or window is opened, releasing a relay that then closes to activate the buzzer. This way, you get notified if the circuit is cut.
There are many more ways, some actually measure the resistance of the circuit and alarm if it changes, etc.
Door contacts are typically normally closed (Normal state being when the magnet is in place). What you would do is wire a relay in series with the contact then connect the buzzer to the relay. If you are using a standard Piezo buzzer you don’t need a resistor. If you want to get a little more advanced you could also get a timer to activate when the contact opens or do a latching relay set-up with a key reset.
If you can find a N/O contact where the contact closes when the magnet is removed you can eliminate the need for a relay.