A touch sensor in electronics is used to detect and record physical touch. Also known as tactile sensors, it’s a small, simple, low-cost sensor made to replace old mechanical switches we have seen in the past. It works like a switch, where when there’s contact, touch, or pressure on the surface of a touch sensor, it opens up an electrical circuit and allows currents to flow through it. Here we design a touch alarm by using IC555 and a touch sensing plate, it senses human touch and gives a louder alert through a buzzer.
Hardware Required
| S.No | Components | Value | Qty |
|---|---|---|---|
| 1 | IC | NE555 timer | 1 |
| 2 | Buzzer | 9v | 1 |
| 3 | Transistor | SL100 | 1 |
| 4 | Resistor | 100K,1M | 1,1 |
| 5 | Trimpot | 100K | 2 |
| 6 | Capacitor | 47uF,0.01uF | 2,1 |
| 7 | Metal Touch Plate | (coin) | 1 |
| 8 | Connecting Wires | – | – |
| 9 | Battery | 9V | 1 |
Circuit Diagram
Working Explanation
As we can see, the IC 555 is the main part of the circuit. Here resistors R3, R4, and capacitor C3 operates as a timing component, by varying the R4 value we can obtain different timing output at the output pin 3. And the SL100 transistor reacts as a switch to connect the buzzer with bias. Resistor R1 and capacitor C1 change output wave shape as ramp depend on R1 resistor value the. Now when the touch plate senses any touch, the buzzer will produce different types of alarm sounds. This touch alarm circuit uses a 9-volt bias supply, so we can use a general-purpose 9-volt battery for portable applications.
Applications
- It can be used in robots, enabling basic movement and the ability to detect a touch in its surroundings
- Smartphones, automotive, and industrial applications
