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A radio wave alarm circuit

2016-02-20 16:54  
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This article describes a radio alarm circuit. The circuit is very simple, I hope for your help. Circuit transmission waves, IC1a, together with a sensor (try 20 cm x 20 cm layer of tinfoil) oscillating slightly more than 1 mhz. This is an audio modulation frequency (a continuous beep) IC1b (MC14093BCF) generated. When a hand or a foot proximity sensor, the frequency of the transmitter (IC1a) decreased significantly. Suppose now that the circuit transmission in a megahertz. Assuming your radio tuned to a frequency slightly lower than this. 1 mhz transmission will not hear the radio. But put a hand or a foot proximity sensor, transmitter frequency will drop, you will hear a beep radio. The antenna to a multiplug adapter into the power supply, you will find every wave propagation of radiation in your house. Will now be an appropriate medium wave radio tuned near some wires or plug point in your house, and an early warning system settings. Instead of using an aluminum foil as the sensor, you can use a doorknob, or burglar bars. Or you can use the buttons and series resistor (wired in series, 33 k resistor - button to short out) to reduce the frequency of IC1a(IRF610 ), so activate the system via a push-button switch. In this case, the radio is tuned to a frequency just below the transmitter. This circuit is not new, but it proved so useful, simple and cheap, it is worth building. 

radio wave alarm


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