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Simple Touch Controlled Potentiometer Circuit

This touch control potentiometer circuit one just need to tap it and it will start to work.

No need to turn knob or move the slider it just touches the sensor and it changes the resistance or voltage.

It uses capacitive sensing which means that when one contacts it, the body will act as a switch.

So cool no?

Circuit Working:

Parts List:

ComponentQuantity
Resistors (1/4 watt)
100k 2
Capacitors
Ceramic 1µF1
Ceramic 47pF2
Electrolytic 10µF 40V2
Electrolytic 100µF 83V2
Semiconductors
IC 31302
Touch Pads (pairs)2 pairs

This touch potentiometer circuit uses IC1 CA3130 which is a op-amp with very high input impedance.

When finger touch sensor Se1 capacitor C2 MKT type get charged through skin.

This make IC1 output voltage go down slowly to zero.

If the touch sensor Se2 is used instead opposite thing happen like voltage will go up slowly until same as power supply.

After finger is removed output voltage stay same because C2 hold the charge.

But slowly slowly voltage drops to about 2% every hour.

This kind of touch potentiometer is useful in many things where need of a potentiometer that work by voltage but not by hand turning.

If someone does not want touch sensor then a normal switch or button can be used just to put 1M resistor in line like mentioned in circuit diagram.

Formula:

This touch control potentiometer circuit works using capacitive sensing and feedback.

To understand when comparator changes its output from high to low, or low to high then we need to know voltage level where this will happen.

Comparator check difference between sensor voltage and a set reference voltage.

Lets say:

When Vcap become same as Vref then comparator changes output.

So we say:

Vcap ​= Vref​

This is point where switching happen.

Exact behavior like how fast it will switch or if small delay is there depend on comparator IC used.

Datasheet of IC will give that information about hysteresis, speed etc.

If IC 3130 is name of special or unknown chip then please give more details or datasheet so one can understand better.

How to Build:

Below mentioned are the steps to build a Simple Touch Controlled Potentiometer Circuit:

Keep all parts ready:

Plan circuit design:

Put IC1 CA 3130 in place:

Add capacitor C2:

Connect touch sensors:

Add resistors:

Power the circuit:

Test the circuit:

Finish build:

Optional:

Note:

Conclusion:

This Simple Touch Controlled Potentiometer Circuit is easy and smart way for people to use electronics.

It helps a lot when space is small or place not good for normal knobs or buttons.

These circuits are used in many things like home gadgets, factory machines and human computer systems.

References:

Potentiometer Circuit Design

Potentiometer

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