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PCB Tech
Touch switch PCB circuit-introduction to simple circuits
PCB Tech
Touch switch PCB circuit-introduction to simple circuits

Touch switch PCB circuit-introduction to simple circuits


When it comes to tactile sensors, the touch switch circuit PCB is the simplest. Despite their simplicity, these amazing technologies are everywhere. For example, a touch screen is just an array of touch switches on the top of the display. They also have a wide range of other applications, including wall switches, lights, and even public computer terminals.

This article will provide you with all the information about the touch switch PCB circuit. This is all you need to add modern touch facilities to your electrical or electronic equipment.

How does the touch switch PCB circuit work?

The touch switch PCB circuit is essentially just an ordinary switch PCB, albeit with special sensors. In this case, when the sensors receive some stimulus changes, they will react by turning off the switch. In turn, it allows current to flow. The type of sensor used usually determines the internal workings of the switch. The touch sensors that make up the modern touch switch type are classified as follows:

Capacitive touch switch. They use the capacitance of the human body to trigger the current, thereby controlling the opening and closing of the switch.

Resistive touch switch. – This type relies on contact pressure to reduce the resistance between two conductive surfaces.

pcb board

Piezoelectric touch switch. – These are less common in many modern applications because they are based on the mechanical bonding of piezoelectric ceramics. They are suitable for insulating and conductive materials, but the production cost is higher.

7 different touch switch circuits

There are many types of touch switches, each of which is an important electronic component in the device that uses them. Common types include:

1. A simple touch switch circuit

For this circuit, you only need a MOSFET and a relay. They use as low as 9V DC power supply voltage to the circuit's power work. Its working principle is that when you touch the Ground and Gate terminals, the electrical appliance is in the OFF state. When the gate and the power supply are contacted, the switch is in an on state.

2. Tact switch circuit PCB using 555 timer

This relatively simple ON and OFF touch switch circuit has a lot in common with the voltage 2 groups. The key differentiating factor is the included integrated circuit timer. These may be NE555 or LM555. In this case, the touch switch circuit has two touch pads, one for each state. It works by using the high input impedance of the 555 IC trigger pin. The human body's induced voltage then rises for the time determined by C1 and R1. After that, the transistor drives the relay, which in turn drives the load.

3. The touch toggle switch circuit using NAND gate

Here, the digital 4011 logic gate forms the basis of the touch switch circuit. The second pin on the IC is "HI" logic. Touching the board connected to the second pin will produce high logic. When there is no contact with the plating, there is low logic. The inclusion of a 22 ohm resistor on pin 1 makes the circuit easy to touch.

4. Touch to activate the switch circuit

This type is often used for integrated digital circuits. It uses a single metal plate and works like a typical ON and OFF switch. The switch circuit uses the IC to obtain electrical signals from the finger. This is the digital signal that triggers the OFF or ON state change.

5. Simple touch switch using transistor

It is an updated version of the original simple ON and OFF touch switch circuit. When the IC that controls the switch operation proves to be troublesome, it is usually the original substitute. A simple touch switch uses only one transistor. When the switch requires a relay, the A and B contacts are connected. When the B and C contacts receive stimuli from the touch, the relay is released.

6. Use UJT's touchpad switch circuit

As the name suggests, it uses UJT 2N3819 as the main switching element. This is beneficial when the switch is part of the device that is not always close to the wire. By touching metal 1 and 2, the switch opens. Touching metals 2 and 3 will trigger the relay, resulting in an off state.

7. Touch motor controller circuit using SCR and Schmitt trigger

Compared with other types, this type is quite complicated. Touching the metal plate in the circuit will cause the Schmitt trigger circuit to obtain a signal from the oscillator circuit. It also pushes the bias current to the base of Q1-2N5088. This will trigger SCR1 which drives a 12V motor.

Building a touch switch circuit is not as complicated as it used to be. Today, basic electronic components can be used to replace complex touch switches and expensive microcontrollers. This means that using components such as transistors and resistors, you can build a simple touch switch circuit.

Project components

First, the components required for this project include:

Breadboard or our printed circuit board (PCB).

A 9 volt power supply

Connection line

2 Hard copper wire or metal strip

BC547 NPN transistor

5mm LED

A 270 ohm resistor

100k ohm resistor

To build the circuit, the steps you need to follow are as follows:

1: Connect the BC547 transistor on the breadboard or PCB circuit board.

2: Use a jumper to connect the base pin of the first transistor to the emitter pin of the second transistor.

3: Connect a 100K ohm resistor between the collector pin of the second transistor and the VCC pin.

4: Connect the 270 ohm resistor and LED to the collector pin of the first transistor.

5: Use another jumper to connect the emitter pin of the first transistor to GND.

6: Connect a metal strip between the 100K ohm resistor and the Base Pin of the second transistor.

After completing all these steps, you can continue to see if the circuit is working properly. Touch the metal strip connected to the circuit to test if it works as expected. This simple switch can have a wide range of applications. For example, you can use it to detect stray voltage or static buildup. Another common use case is in dusty or humid areas where typical switches are not suitable.

in conclusion

It is beneficial to touch the switch circuit PCB. Fortunately, incorporating them into modern electronic design has never been easier. They are easy to build, especially with the correct PCB components. You can check out some of our best components. That's all you need to start a do-it-yourself (DIY) project using the touch switch PCB.