Room Lighting Control in High Humidity Environments
This circuit serves the purpose of safely toggling domestic lighting on and off in rooms characterized by very high humidity levels. The mechanism involves the utilization of a flush-mounted detector, discreetly positioned within the wall. This detector is designed to sense magnetic field fluctuations triggered by the presence of a hand, subsequently facilitating control over an AC power switching system. As a result, the control of room lighting is seamlessly executed through the wall covering, eliminating any necessity for exposed electrical components. This design prioritizes safety, convenience, and a discreet appearance in high-humidity environments.
Capacitive Touch Lighting Control System
In this system, the core functionality revolves around a specialized IC, the QT113A from Quantum, which has now become part of Atmel after an acquisition a few months ago. This IC operates by generating a pulsed magnetic field while employing a capacitive measuring system to detect variations. Any detected change in the magnetic field prompts a toggling of its output. To ensure precision, a series of filters are incorporated, and the detection process requires confirmation three times before the processor triggers the output, thereby preventing unintended activations. IC3 features a self-calibration mechanism, allowing it to adapt to external variations effectively. The pulsed operation not only reduces radio frequency emissions but also conserves power.
The electrode, essential to the system, is constructed from a piece of copper-clad PCB board, approximately 5 × 5 cm in size. This board has been prepared by removing the photosensitive film to enable soldering of a connecting wire. It’s crucial to maintain a few centimeters of separation between the electrode and the electronics board for proper functioning. This setup prevents the use of a double-sided PCB with SMD components on one side and the electrode on the other. The sensitivity of the detector is influenced by the value of capacitor C1, which needs adjustment based on the specific environment and desired sensitivity level.
Control Logic and Load Handling
IC3 produces an oscillating signal as an indication of its operational status. To harness this information and manage load switching, a small controller is employed, facilitating the control of an opto-triac and a triac. The microcontroller is programmable via a standard ISP connector. A compact transformer enables the integration of a 5 V power supply unit on the board and provides isolation from the AC power line. The circuit ensures isolation between the output and the AC power, utilizing an opto-triac. However, it’s crucial to note that one part of the circuit is directly connected to live AC voltage.
Construction and Application
All components utilized in this system are surface-mount devices (SMD) yet are designed for straightforward soldering using a conventional soldering iron. The PCB seamlessly fits into an electrical back-box, such as the Legrand Beatbox, installed in locations like bathrooms. A simple touch of the designated tile with a finger is all it takes to effortlessly turn the light on or off, providing a user-friendly and discreet lighting control solution. www.elektor.com/090537