7 simple touch switch circuit projects

There is many how to make a simple touch switch circuit diagram. We can build them easily. Because of using basic components, transistor, UJT, and popular IC like 555 timer, 4011 CMOS, flip-flop IC.

touch switch circuit diagram

We just touch the sensor lightly. Our bodies have resistance. It makes the current flow through the circuit is changed. The circuit will recognize and then turn off the electrical appliances.

There is 5 circuits diagram list. You can choose the one you want.



Touch switch circuit using 555 timer

This is a simple touch on and off switch circuit.  It has a part compares with voltage 2 group. In circuit uses an integrated circuit timer, LM555 or NE555.

touch switch circuit using 555 timer
Click to view touch switch circuit using 555 timer


How it works

There are 2 touchpads for turn on and turn off to detect the change of voltage. When we touch the first touchpad between pin 2 and ground. Our finger has resistance. So, it passes the current (Hi) to ground. Then, at pin 2 is Low logic. It causes the IC-555 runs.  Next, the high voltage goes out of pin 3 (the output).

After that, we touch off the touchpad is between pin 6 and a power supply voltage. The current flows through our finger to pin6.  The logic changes to low voltage.

Also, the output switches to Low.

We can apply the output to control other circuits like LED, relay and input circuit.

Read below! You may be able to get more ideas about Touch Switch

Touch toggle switch circuit using NAND gate

This circuit uses a 4011 logic gate digital as the bases of the touch switch.

It is Standard and very easy because I used a Gate of IC 4011. In circuit at pin 2 of 1/4 IC is Hi logic “HI” alway.

If touching the plate connected to the 2 number. So the logic output is Hi, but don’t touch is Low logic.
The 22M resistor on pin 1 causes the circuit to be very sensitive to the touch.

Standard Touch Switch by Gate of IC 4011

Touch Switch circuit project

Today we let to play a simple digital circuit. It is a One shot touch switch control. I use IC-4011 digital CMOS is base of a circuit. It is set to form as flip-flops.

The Logic “HI” at an output when Your finger touchpad and is a time delay for 3 seconds. Which we can determine this pulse time delay (one-shot) by C1-electrolytic capacitor of 47uF (microfarad).

After that touching the plate connected, so well pulse output. Detail more Please read in this image circuit and see video below.

Simple one shot Touch Switch using IC4011

In this circuit not have LED display, thus I add them in a breadboard, so that show working of this circuit. we use 1k-resistor is connected with series it to control proper current flow it.

Touch activated Switch circuit

This is touch switch be simple again the circuit. It uses an integrated digital circuit is important equipment, and use volt power supply low just 9V. By using single metal.

Touch Switch circuit By IC CD4001,CD4020

It works in the character turn ON and turn OFF. By when a touch for the first time turns ON, but enough for the second time turn OFF.

The circuit composes IC CD4001 take an electric signal from a finger become the digital signal for change. The IC CD4020 be the counts two circuits or the divides circuit by two.

Subsequently, submit give the transistor drive Load next.

Simple touch on and off switch circuit

In the previous circuit, we use JK-flip-flop in as RS-FF. We will use pin R and S of flip-flops, by stores data of pin J, K and CK(clock). The experiment about Digital touch switch circuit using JK-flip-flop as RS-flip flop just to use your finger to touch them only also can turns ON-OFF circuit, this switch type is widely popular.

We will use the JK-FF of CMOS type,is MC14027 as before. The principle of the touch switch is special feature of CMOS that has very high input resistance. When use finger touch input cause an inductance as high states or logic “1”, result the RS-Flip-flops of CMOS works which use RS-Flip-Flop circuit.

In this experiment, should not use general battery as the power supply because not enough inductance, the circuit may works.

The experiment is shown in Figure 1 the most form look like before circuit , just use JK-Flip-Flops type as RS-Flip-Flops only, pin R and S will connect to 2 metal plate, to reduce input impedance lower and connects resistors of 22 Mohms to ground. For J, K and CK not use to short circuit to ground.

simple touch on and off switch circuit

The experiment start from use finger touch to the plate at terminal S, flip-flops will be reset and relay will works. But we touch at R flip-flops will be reset and reset will stop. This metal plate will use the aluminum foil used to wrap food such as roast chicken, grilled fish., Which are sold in supermarkets, or. Shopping mall. This experiment is shown in Figure 2

simple touch on and off switch circuit perforated board

If you use a relay larger than that setting. To can turn ON/OFF higher load. You should know the resistance of the relay coil. Such as a KOIKE model – MAA 12V is a small relay. There are the resistance of coils about 400 ohms

When use driver transistor will use the only current of 30mA. If relay uses resistance lower than this. So require more current to drive them, and reduce an R3 value lower to CMOS can provide current to the base of transistors more higher. But should not reduce the value of R3 as lower than 5 Kohms. Because will cause the CMOS provided too much current.

Simple touch switch using transistor

This Simple touch switch using a transistor is the touch switch is updated from the original version. Which use IC to control the operation cause difficult for the electronics beginner. So this circuit is thought to are suitable because uses TR purely. When was broken also a simple repair. and More cost-effective equipment. But The application is easy namely when we want to relay connected A and B contract. But when we want to relay release We also touch on the B and C.

The working principle
When we touch at point A and B will have some current from point B through our finger to point A. Which base of TR2 this current will makes TR2 conduct current between pin C and E. This current will pass R-820 ohms into pin B of TR3 cause TR3 conduct current as well.

Figure 1 the cheap touch switch circuit using transistor

And this current will pass from pin BE of TR4. When TR4 has current flow through pin E-B will make it also conduct between pin E-C. Thus relay so derived the current and there is LED glow to indicate to we know once that the relay is running now.

While at pin C of TR4 will have higher voltage nearly equal this point voltage that through R 4.7M to pin B of TR2 cause current to flow continuously even we will release the touch point. The relay will remain active. When we want to make the relay stops working. We also touch points B and C. The some current will flow through our fingers from point B to point C.

And go to pin B of TR1, cause TR1 conduct, thus current pass through an R-4.7M instead will in pin B of TR2, Returned to the ground via pin CE of TR1, making TR2, TR3, TR4 not conduct current, stop conduct the relay so release contacts apart. Until the touches point new AB.

How to builds
This circuit uses the 9V power supply and all resistors use size ¼ W, Relay size 9V rate of the flow resistance of the relay depends on the needs of applications. But usually, use the 1-3 A. D1 is for reverse voltage protection relay to the circuit. The C-10uF 16V makes supply voltage is smooth. and C-0.01uF, C-22uF prevents noise from the air that passes through the fingers when touched. You can see the PCB layout in Figure 2. and the components layout as Figure 3 which if you are a lover of electronic will build it easily sure.

Figure 2 the PCB layout of cheap touch switch using transistor
Figure 3 the components layout and wiring of the cheap touch switch.

The components list
TR1-TR3______C1815 or C828____45V 100mA NPN Transistor
TR4_____________CS9012____________45V 800mA PNP Transistor
LED1____________LED as you need
C-10uF 16V_______Electrolytic capacitor
C-0.22uF 50V_____Electrolytic capacitor
C-0.01uF 50V_____Ceramic capacitors
R-470K________1/4w +5% Resistors
RY-Relay 9V
Others components

Touch plate switch circuit using UJT

Touch Switch using UJT 2N3819

This is a very Simple Touch Switch Circuit. It used UJT 2N3819 is Main part numbers should set up this outside building circuit.

When staying far from the electric line or Power Line very much. Enough touch at in front touch 1 metal and 2 make Relay work ON getting.

When but urgent touch 2 metals only make Relay stop work OFF get. For within a building must enhance the part mends or in front touch 3 metals with following circuit picture.

The Relay use 6V to 9V sizes and Volt supply use 6V to 9V levels all right. Request friends have fun Touch Switch using UJT 2N3819

This Post Has 2 Comments

  1. i just need a circuit containing 3 relays with timer ic

  2. Please give me detail info or name of reference books to make touch circuit by using IC555.

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