This is the cheap fire alarm circuit that Uses the principle of infrared sensor smoke detector. When cause events fire. The principle is simple and affordable. Ideal for general home use.
“Fire” is a word no one wants to hear. Or would like to make it happen. Because its losses occurred.
Although the fire was not serious and indefensible If we do not underestimate.
Power lines and electrical equipment to last for good, so decadent, it should not cause it to happen.
An alarm circuit to know that fires has many form depending on the type of sensor that get to application, shuch as the radiation heat form, the smoke detectors. Which most of such circuits, often expensive and difficult to buy.
But we use the infrared light system as smoke detector. So easily created. Save more than And of course work efficiency of 100%.
This project include 2 section, are 1. The master unit which is the alarm signal generator and notice to point fire. And (2.) is the detector point which Separate sub. for install various rooms up to six points. And may be extended over a number of the detector point. If you have a large home and has room more than 6 rooms
Characteristics circuit active as shown in Figure 1.
How This Circuit works
In Figure 1 is master unit circuit which consists of the power supply circuit Including Transformer-T1 will reduce voltage at home to 6 volts at secondary, the Diodes -D1,D2 is connected as full wave rectifier by have capacitor-C1 is filter to smooth voltage.
Figure 1: Fire alarm circuit with Smoke detector
IC1 serves as the frequency generator of 1.5 Hz to get output at pin 3, then to collector of Q1 by normal input at base of Q1 will be 0. Since working of the inverting IC2. But in the event of Fire the output of inverting will be positive. Cause transistor-Q1 work to bias drive base of Q2 runs. The buzzer that connect at collector will sound fully to alarm will know immediately that fire! By we can know that Occur at any point. By looking at the tube, LED D3-D9.
In case you want to connect buzzer or the alarm circuit for example sirent etc, There are more efficient that use in this circuit has small size so may increase current output with connecting the relay circuit in to circuit as Figure 2 Replace existing doorbell circuit.
In the heart of the sensor circuit is the Infrared transmitter (D10) and Infrared Receiver (Q10).
In normal operating conditions. Infrared light from the transmitter will be shined to the Receiver Making receiver has an impedance lower down. voltage at base of Q9 will low, making transistor-Q9 not work. The voltage at collector will have high value equal voltage at point A.
The voltage will cause the output of IC2 is 0. And while transistors-Q3-Q8 will not work.
In the event of a fire. The smoke to obscure the infrared beam Can not pass to a receiver, or a quantity less. The resistance of receiver will rises up, cause the voltage at base of Q9 is positive. The Q9 will work voltage at collector will reduce (as low)
Fire up that first set. The voltage at inverting input pin 1 will have low level , cause get the output at pin 2 is positive passed diod-D11 to base of Q1 make Q1 work as above.
Meanwhile, low voltage is fed through R4 to base of Q3 cause Q3 work, The LED-D3 will glow, making us more aware of the fire.
The advantages of this detector is in case of fire a wire to the sensor broken down This alarm also working.
How to builds
First of all assemble the components, the circuit, on the PCB, as shown in Figure 4. By assembly equipment in the correct finished Then the experiment circuit together to test the functionality.
Figure 4 The Single-sided PCB layout and components layout
Testing may be done by spraying smoke into the box at the receiver, or Try to find a paper shade, the circuit to work immediately.
Finished deployment By the master unit may be installed inside the bedroom or That think that people in the house to hear the most obvious warning sign.
For the detector Should be installed at the top of the wall or ceiling Above the critical point is expected to be on fire, like a fireplace, sofa, rug, etc. as possible.
The components List
IC1___NE555___Timer IC___________= 1 pcs.
IC2__CD4069_____Inverter CMOS IC___= 1 pcs.
Q1,Q9___BC547__ 45V 100mA NPN Transistor
Q2___BC337__ 50V 800mA NPN Transistor
Q3___BC557__ 45V 100mA PNP Transistor
C1____1000uF 16V____Electrolytic capacitors
C2____1uF 50V_____Ceramic capactors
C3,C4___0.1uF 63V___Polyester capacitors
D1,D2___1N4002___100V 1A Diodes
D11-D16___1N4148____ 75V 150mA Diodes
R1_______100K____Resistors 1/4W 5%
R2_______470K____Resistors 1/4W 5%
R3,R17____47K_____Resistors 1/4W 5%