Latching Touch Sensitive Alarm Electronic Circuit

Latching Touch Sensitive Alarm

Electronic Circuit

The latching mechanism is involved in this electronic circuit, when the probe is touch by an external source the buzzer keeps in ON position until the state is changed by a momentarily push button, though output is connected to the 555 timer IC. The latching is intensively used in burglar detection, capacitive touch detection circuits etc. it also detects with the negative touch of an object also when they are very near. So let’s make our latching circuit and understand the concept behind it.

Principle

When we touch the open wire probe, the voltage across the circuit 555 timer regulates and buzzer makes sound, until it is turned OFF with the help of momentarily push button. It has wide range applications and uses in burglar and home security system. When the negative object are bring close to the probe, the buzzer makes a sound. Let’s do the project in sequence to grab the points effectively.

Components Required:

1. 555 Timer IC (1) get it from here

2. Buzzer (1)

3. BC547 Transistor (1)

4. LED (1)

5. Momentary push button

6. 10k, 270 ohm resistor(1)

7. Bread board

8. Connecting wires (asrequired)

9. DC Power supply(5-12)V

Circuit Diagram:

Procedure:

1. Place the 555 Timer IC on the bread board with its notch facing up

2. Connect pin 4 of the IC to the positive rail of the bread board

3. Connect pin 1 of the IC to the negative rail of the bread board and reset pin to

4. Connect pin 6 to the positive rail of the bread board and touch contact to the pin 2 of the 555Timer IC.

5. Place an LED on the bread board

6. And connect anode to the 555 Timer IC

7. Connect cathode of LED via series resistor of 270 ohm

8. Now connect the buzzer between the output of 555 timer IC and negative rail.

9. Now connect the transistor (BC547) such that emitter is connected to negative pin of 555 timer IC

10. Connect 10k resistor between the transistor and the timer IC

11. Connect the collector pin of transistor to pin 2 of IC

12. Now insert momentary push button on the bread board, with terminal connected to collector and positive rail.

13. Connect the power supply to turned ON the circuit

14. And when we place our hand or object closer to the probe, the buzzer makes the beep sound and LED flashes indicating the circuitry operation is performed.

when we push the momentary button the LED turned OFFand buzzer stops making sound, the circuit is shifts to quasi state.

So this is the basic latching operation for the touch detection circuits, having intensive application in home security system and burglar action protections. What are you waiting for make the project to understand the concept perfectly.

Thank You

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