How to build simple battery powered DIY Burglar Alarm - with automatic Exit, Entry and Siren Cut-Off timers.

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Garage / Shed Alarm - Siren Cut-Off Mod

Free Circuit

Simulation
This small modification will add a siren cut-off timer to the Garage / Shed Alarm. The siren will sound once only - for about 20 minutes or so. The length of time depends on the values of R9 and C5. When it switches off - it won't sound again - until the next time the alarm is set - and subsequently activated.

The only change to the Original Circuit is the removal of the connection between pins 8 & 9. These two pins must now be controlled separately - and independently. The existing components - R6, D3 & C4 - are all transferred to pin 9. And the new components - R8, R9, D6 & C5 - are connected to pin 8. The necessary changes to the veroboard layout - are described below.

Circuit Description

The following Circuit Description only covers the operation of the Siren Cut-Off Timer. It should be read in conjunction with the fuller description of the Garage/Shed Intruder Alarm circuit.


Changes To The Layout



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Basic Schematic Ron's Circuits Write To Ron More Free Circuits Circuit Description