Allarm antifurto

Posted on Feb 6, 2014

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), should your budget forbid

Allarm antifurto
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a commercial one. Wireless sensors aside, our schematic provides also inputs for wired sensors. Such sensors are treated as normally closed contacts, that break when someone enters their range or opens a door or window. It is often the case that they provide a second anti-tamper contact, which breaks if you open the case or attempt a sabotage. Therefore we need two inputs: one for connecting anti tamper and immediate contacts and another one for connecting the delayed contacts. The "immediate" input is connected to the Nutchip pin IN1, and the "delayed" on to pin IN2. As the wires are usually long enough to collect any sort of noise and interference, a couple of identical networks provide quite an energic cleanup and clipping on the input signal before it arrives to the chip. These networks are built around R7-R9-C5-DZ2 and R6-R8-C4-DZ1 respectively. All of the output are connected to a LED diode (DL1, DL2, DL3, DL4), in order to display the status of the main board. A siren is connected to the fourth output, through RELAY1. As this circuit is designed for uninterrupted service, brown-outs are a possibility that cannot be excluded. A brown-ut is a big decrease in the mains voltage level that does not end in a black out. Brown-outs are dangerous for electronics devices, because it can result in improper or partial reset with impredictable consequences. This is why whe have added IC2, a special voltage detector and RESET...

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