Touch switch or proximity detector

This circuit is activated by an increase in capacitance between a sensing electrode and the ground side of the line. The sensitivity can be adjusted to trigger when a human body is within inches of the insulated plate used as the sensing electrode. Sensitivity is modified using a 1 megohm potentiometer, which sets the anode voltage level before clamping. Additionally, this sensitivity is proportional to the area of the surfaces opposing each other.

The described circuit operates on the principle of capacitive sensing, where the capacitance change is detected as a human body approaches the sensing electrode. The sensing electrode is typically designed as an insulated plate, which acts as one plate of a capacitor, while the ground serves as the other plate. When a person comes within proximity of the insulated plate, the capacitance between the two plates increases due to the additional dielectric constant introduced by the human body.

To tailor the circuit's responsiveness, a 1 megohm potentiometer is utilized. This component allows for fine-tuning of the sensitivity level, enabling the circuit to respond to varying distances and conditions. By adjusting the potentiometer, the anode voltage level is modified, which in turn affects the threshold at which the circuit will activate. This feature is particularly useful in applications where the detection range needs to be customized based on environmental factors or specific user requirements.

Furthermore, the sensitivity of the circuit is directly proportional to the area of the surfaces facing each other. This means that increasing the surface area of the sensing electrode or the ground plane can enhance the sensitivity of the circuit. Consequently, careful consideration must be given to the design and placement of these surfaces to optimize performance. The overall design of the circuit should also include appropriate filtering and noise reduction techniques to ensure reliable operation in various environments.This circuit is actuated by an increase in capacitance between a sensing electrode and the ground side of the line. The sensitivity can be adjusted to switch when a human body is within inches of the insulated plate used as the sensing electrode.

Thus, sensitivity is adjusted with the 1 megohm potentiometer which determines the anode voltage level prior to clamping This sensitivity will be proportional to the area of the surface opposing each other.