Resistive moisture sensors use exposed PCB traces to detect water. Rain needs AC because near‑distilled drops have high resistance. An inverting Schmitt‑trigger oscillator drives the sensor; a high‑pass, gain stages, rectifier, and integrator yield a logic level that lights an LED or actuates gear like a sunroof. The build demos a KD9561 sound chip. Notes touch solder, lead, and thin gold plating.
DALI (Digital Addressable Lighting Interface) is a two-wire digital protocol for controlling up to 64 devices per bus, scalable to thousands. It uses simple cabling with flexible topology and supports two-way communication for control and status monitoring. Its limitations include command delay preventing dynamic effects and the need for a gateway for smart home integration. Evolving standards include DALI-2 for human-centric lighting and DALI+ for IP-based control.
Smart lighting uses digital protocols for automated control, enabling features like individual fixture addressing, light scenes, and two-way communication for status monitoring. It integrates with smart home systems via protocol converters. Benefits include enhanced comfort through predictive lighting and biodynamic cycles, increased energy efficiency, and new functionalities like voice control and AI-driven automation that learns user habits.
Analog protocols 0-10V and 1-10V, developed in the 1970s, are still used for dimming LED and fluorescent lights. 0-10V uses 0V for off and 10V for 100% brightness. 1-10V uses 1V for minimum dimming and 10V for maximum, requiring a separate switch for power. While signal degradation limits long-distance use, their low cost makes them prevalent in hybrid systems and for street lighting via standardized connectors.
A weight sensor, or load cell, uses strain gauges bonded to a bending beam. Their electrical resistance changes minutely when force is applied, stretching or compressing them. These gauges are arranged in a Wheatstone bridge circuit, producing a small voltage change. This signal is amplified and converted to a digital reading by an integrated circuit like the HX711, which a microcontroller can then interpret as a weight measurement.
