Allarm circuit

Posted on Feb 5, 2014

Making yourself an alarm is both useful and interesting: but the best part is when you take the remote control out of your pocket, and switch on the alarm while saying to your friends: `I`ve done it in a weekend`. Making yourself an alarm gives you maximum flexibility: as this project works according to the Nutchip truth table, you can change it to suit your needs. Some people

Allarm circuit
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would like to have like a "panic" button, in order to sound the siren. Some other pepople need a very long time to leave the house. Or you might be looking for an alarm that keeps that special sensor on even if you are at home. Possibilites are unlimited! All of these sensors can be configured for either immediate or delayed alarm. Delayed alarms are required to allow some time for the legitimate user to get in an switch the alarm off. Let`s approach the main schematic as if it was made of blocks in order to understand it more easily. These blocks are: radio front end, contact inputs, reset generator, outputs, power supply and, of course, core logic provided by the Nutchip. A wireless alarm sensor is similar to a remote control. When someone enters its detection range, a wireless sensor sends an impulse train as if someone pressed a special remote control key. A radio receiver module on the main board detects the pulse train, and forwards it to Nutchip` REMOTE control pin. The Nutchip decodes the signal, differentiating between immediate and delayed sensors (aside from true remote control signals used for switching the circuit on and off). As for all radio-based designs, always remember that a good radio receiver cannot replace a good antenna. The circuit works well with an home made antenna (straight insulated wire), unless if your budget has enough room for a better one. Wireless sensors aside, our schematic provides...

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