Here is the wailing alarm siren circuit diagram: Components List: R1,R5___________ 4.7K R2______________ 47K R3______________ 10K R4______________ 100K Rx______________ *see text C1,C4__________ 100uF/25V, electrolytic C2,C3__________ 0.01uF (10nF), ceramic T1_____________ 2N3702 (NTE159, TUP, etc.) IC1,IC2________ LM/NE555, MC1455P, etc LS_____________ Loudspeaker
This is a 12VDC to 9VDC converter circuit. You may use this DC to DC stepdown converter circuit if you have fixed 12V power supply / battery, but you need 9V power supply for your electronic devices. Scheme Diagram: Components List: R1________ 560 ohm, resistor C1________ 1000uF/16V, Electrolytic capacitor C2________ 100uF/16V, Electrolytic capacitor C3________ 330nF,… Read More »
If you’re interested in RF circuit, then you should know about this basic RF oscillator. This basic RF oscillator circuit is easy to build and the components are not critical. Most of them can be found in your junk parts box. The circuit operated with 9VDC power supply. The L1 antenna col can be made… Read More »
The following diagram is the circuit diagram of basic monostable multivibrator based IC timer 555. This circuit uses only 4 electronic components that are a timer IC, two capacitors and a resistor. Components List: A multivibrator is an electronic circuit used to implement a variety of simple two-state systems such as light emitting diodes, timers… Read More »
This is a very easy and simple LED flasher with only three components: a flasher IC LM3909, a LED indicator and an electrolytic capacitor. The supply voltage is 1.5V, so it can be operated using a 1.5V battery which can be easily found on market. Component list: LED1 _________ Red LED C1 ___________ 100uf/16V IC1… Read More »
This is a simple audio pre-amplifier circuit using single transistor 2N3904. This easy circuit provides good gain to weak audio signals such as electret microphone. Use it in front of an RF oscillator to make an RF transmitter that’s very sensitive to sound. Power supply used for this circuit is wide range from 3VDC to… Read More »
This is the circuit diagram of mini AM Radio receiver. All general purpose transistors should work in this circuit, you can use BC549 transistors for this circuit.
Here the simple and low cost FM transmitter circuit. The frequency range of this FM transmitter should be about 89MHz – 109MHz. Output power is about 9mW at 9V. Components List: Resistors: R1, R6 : 12K R2, R4 : 100K R3 : 22K R5 : 1K R7 : 100R Capacitors: C1 : 10uF/25V C2 :… Read More »
This a two station intercom. It uses two wires to run between each intercom unit. Each is self contained with its own battery, speaker, microphone and amplifier circuit. An LM386 audio power amplifier is used. It is widely available, used a minimum of external parts and is well suited to battery operation. It will give… Read More »