Free electronic circuit design and schematic diagram
This alarm generates square-wave output that sweeps down and up in frequency, producing force field of high-intensity sound inside car, building, or your other properties. In security application for example, this circuit can make a car thieve panics and decide to run before anyone catch his action. D1, C1 and R1 produce triangle waveform by shaping a square wave output […]
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This is a simple circuit of beeper using 555 timer. This circuit can be employed to energize lights, horn, or other signaling device at any desired interval when the mercury switch is triggered. Since the current handling capability of mercury switch is not so high, an SCR is used to handle current drawn by the 555 timer circuit. Chose the […]
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This is Simple Code Lock circuit. This circuit will turn on a relay when the 8-way DIP switches receives the correct code. Here is the schematic diagram of the circuit: There are two different types of DIP, they are piano-key DIP sw and 8-way DIP sw. This circuit will not draw the current if the switch is kept off. This […]
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This is a driver circuit for siren. This circuit usually used for car alarms. To build this circuit, we use VD-MOS FETs. This circuit receives 12 v supply from battery. A microprocessor sends complementary pulse waveforms to the driver circuit as inputs. Here is the circuit : This circuit uses two PHC21025 which each of them contains two FETs. Two […]
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Ionization-based smoke detectors are efficient and cheap, so they are often installed in the house, other outbuildings, and the garage. The Locations of the device is far from house, so we need to transmit the alarm signals back into central home-security system or the house. This is a simple circuit that sense a supply current increase because activation of smoke […]
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This circuit is made to be an alarm, both for home and handbags. If it is installed for home it will placed on door or windows, and if it is installed for bags or handbags it will placed in the bag. This circuit consists of a small magnet and a reed switch. If the magnet looses its contact with the […]
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This alarm siren circuit produce warbling sound, you can use it in your toys or in security alarm. The circuit use two 555 IC oscillator. In this alarm siren circuit, the first oscillator is employed to produce audio frequency. The second oscillator is employed to produce a modulating signal. This modulating signal make this alarm siren generates warbling sound. Here […]
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