Simple Touch Controlled Potentiometer Circuit

This touch controlled potentiometer circuit lets you control things with just a tap.

Forget fiddling with knobs or sliders simply touch a sensor to adjust resistance or voltage.

It uses something called “capacitive sensing” which basically means your body acts like a switch when you touch the sensor.

Pretty cool, right?

Circuit Working:

Parts List:

This sensitive touch potentiometer operates using IC1 CA3130, an operational amplifier characterized by high input impedance.

When the finger makes contact with the Se1 sensor, C2 a capacitor of MKT type charges via the skins resistance resulting in a linear decrease to zero of the IC1 output voltage.

Conversely, when Se2 sensor is touched, the opposite effect occurs.

The IC1 output voltage increases linearly until it reaches the power supply voltage.

Upon removing the finger from the touch sensor the voltage at IC1s output remains sustained by the charge stored in C2.

However, this voltage gradually diminishes at a rate of approximately 2% per hour.

This touch potentiometer circuit finds utility across various applications suitable for situations requiring a potentiometer controlled by variable voltage.

In the event conventional switches or buttons are preferred over touch sensors a 1M resistor can be inserted in series as depicted in the schematic.

Formula:

In a touch controlled potentiometer circuit involves capacitive sensing and feedback control.

Knowing the voltage levels at which the comparator changes its output state (from high to low or vice versa) is necessary to get the precise formula for the comparators behavior in this circuit.

The voltage differential between the capacitive sensor output and the reference voltage supplied to the comparator establishes this switching threshold.

Let us indicate:

V_cap: The voltage coming from the circuit of the capacitive sensor.
V_ref: The reference voltage that is applied to the comparators non inverting input.

When Vcap reaches Vref, the comparator will change its output state.

One way to roughly describe the relationship is:

V_cap ​= V_ref​

The comparators output switching threshold is set by this equality.

The particular comparator integrated circuit IC used and its datasheet parameters will determine the precise behavior (hysteresis, response time, etc.)

If IC 3130 pertains to a particular, little known gadget, kindly supply further information or a datasheet to help with understanding.

How to Build:

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

Prepare the components:

• Gather all the necessary components and ensure they are in working condition.

Circuit layout:

• Design the layout of your circuit.
• Decide where each component will be placed and how they will be interconnected.
• You can refer to the provided schematic or create your own based on the description.

Connect the operational amplifier IC1:

• Place the CA3130 operational amplifier onto your breadboard or PCB.
• Connect its power supply pins V+ and V- to the appropriate voltage levels.
• Connect the output pin to the rest of the circuit.

Connect the capacitor C2:

• Place the capacitor MKT type on the board and connect it to the appropriate pins of the operational amplifier.
• Ensure proper polarity if applicable.

Connect the touch sensors:

• If using touch sensors, connect them to the appropriate input pins of the operational amplifier.
• If using switches or buttons, connect them as per the provided instructions for example, placing a 1M resistor in series.

Connect resistors:

• Connect any required resistors according to the circuit design and schematic.

Power supply:

• Connect the power supply to the circuit ensuring correct polarity and voltage levels.

Test the circuit:

• Before finalizing the assembly, test the circuit to ensure it functions as expected.
• Check the response of the potentiometer to touch or button presses and verify the output voltage changes accordingly.

Finalize the assembly:

• Once the circuit has been tested successfully finalize the assembly by securing components in place and tidying up any loose connections.

Optional:

• Depending on your application, you may choose to enclose the circuit in a protective case or integrate it into a larger project.

Note:

• Remember to double check all connections and component placements to avoid any errors or short circuits.
• If you encounter any issues during testing troubleshoot the circuit by verifying connections and component values.

Conclusion:

Overall, touch controlled potentiometer circuits offer a convenient and intuitive way for users to interact with electronic devices particularly in applications where space constraints or environmental factors make traditional controls impractical.

They are commonly used in consumer electronics, industrial automation and human machine interface systems.

References:

Potentiometer Circuit Design

Potentiometer