Above circuit is an fire alarm circuit which build using a fire alarm sensor component and sound generator component. With simple and cheap component, you can build this circuit for low cost.
The termistor is a fire detector sensor and the NE555 is an audio frequency generator which will resulting the sound of alarm from the speaker.
If you are an electronic hobbyst, you are of course very familiar with this part. This part usually used on PCB, to make the circuit “portable”, easy connect and disconnect to another circuit modul safely without soldering the connector.
A screw terminal is a type of electrical connector where a wire is clamped down to metal by a screw.Screw terminals are commonly used to connect a chassis ground, such as on a record player or surge protector. Most public address systems in buildings also use them for speakers, and sometimes for other outputs and inputs.
A varicap diode also known as varactor diode, variable capacitance diode, variable reactance diode or tuning diode. Varicap is a type of diode which has a variable capacitance that is a function of the voltage impressed on its terminals.
Varactor or varicap diodes are used mainly in radio frequency (RF) circuits to be able to provide a capacitance that can be varied by changing a voltage in an electronics circuit. This can be used for tuning circuits including radio frequency oscillators and filters.
They are commonly used in parametric amplifiers, parametric oscillators and voltage-controlled oscillators as part of phase-locked loops and frequency synthesizers.
This is a simple 220V LED flasher circuit. This circuit is intended as a reliable replacement to thermally-activated switches used for Christmas tree lamp-flashing.
Component Parts:
R1 = 100K
R2,R5 = 1K
R3,R6 = 470R
R4 = 12K
C1 = 1000µF 25V
D1-D4 = 1N4007
D5 = SCR P0102D
Q1 = BC327
Q2 = BC337
SK1 = Female Mains socket
How it works:
The following is a schematic diagram of a lamp brightness control. Lamp used is a light tube with a voltage 3V. You can replace the lamp with other lamp types, such as LEDs.
How the circuit works:
IC1 works to generate 150Hz square wave which having a variable duty-cycle. When potensiometer P1 is fully rotated towards D1, the output positive pulses appearing at pin 3 of IC1 are very narrow. Lamp LP1, driven by Q1, is off as the voltage across its leads is too low. When potensiometer P1 is rotated towards R2, the output pulses increase in width, reaching their maximum amplitude when the potentiometer is rotated fully clockwise. In this way the lamp reaches its full brightness.
