This is the diagram of heat detector circuit which already integrated with siren circuit in the output. This circuit applies a complementary pair comprising NPN metallic transistor T1 (BC109) and PNP germanium transistor T2 (AC188) to detect heat (because of outbreak of fire, for example) in the area and activate a siren/alarm. The collector of… Read More »
This is a mini FM transmitter built and powered using 2 transistors, designed by Tony van Roon. This small transmitter is simple to build and its transmissions could be picked up on any common FM radio. It possesses a range of approximately 1/4-mile (400 meters) or even more, depending on the line-of-sight, obstructions by big… Read More »
The following diagram is the circuit diagram of voice transmitter which use FM signal carrier to transmit the vioce signal to the FM receiver device. Components List: R1 = 4.7K R2 = 330 ohm C1 = 0.001uF (1nF) C2 = 10-40pF C3 = 4.7pF Q1 = 2N3904 L1 = see text Misc = Electret mike,… Read More »
Simple and easy build of sensitive FM transmitter circuit. The circuit only requires 2 transistors to work. *L1 = 0.1 Uh, 6 to 8 turns of 22 ga. hookup wire close wound around a 1/4 inch diameter non-conductive core such as a pencil Circuit Notes: Typically the default for the capacitors model is ceramic, preferably… Read More »
The following is LED Flasher circuit which use 2 transistors for LED switching. The circuit works similar to flip-flop operation. Components List: R1 = 10M ohm R2 = 1K – 100K ohm R3 = 470 ohm C1 = 0.47uF – 10uF/25V D1 = 1N914 Q1 = 2N3904 Q2 = 2N3906 Led = High Brightness Red… Read More »
Above diagram is a very easy and efficient receiver for actuating garage doors, starter motors, alarms, warning systems and many some other possibilities. The SCR, which has a extremely low trigger current of 30 uA is typical — it demands an input electricity of just 30 uW to activate the relay. A high Q tuned… Read More »
This is the sound generator which will simulate British police car siren. The circuit is built using 2 pieces of timer IC 555 to generate sound frequency. How the circuit work: