Sensors, Controllers, and Non-Dimmable Drivers: Building Simple Smart Lighting

Smart lighting does not have to mean dimming. A large share of the energy savings attributed to 'smart' systems actually comes from one simple mechanism: turning lights off when nobody is there. Occupancy sensing, daylight response, and scheduling can be implemented with non-dimmable constant voltage drivers and a relay or contactor — no DALI, no 0-10V, no wireless dimming protocol required. For spaces where light levels are fixed but occupancy varies — warehouses, corridors, stairwells, restrooms, parking garages, storage rooms — this simple architecture delivers most of the benefit of a full smart system at a fraction of the cost and complexity.

The building blocks are three: a sensor, a control device, and a switchable power path. The sensor detects occupancy (PIR, microwave, or dual-technology), daylight (photocell), or schedule (time clock). The control device interprets the sensor signal and operates a relay, contactor, or solid-state switch that makes or breaks the mains supply to the driver. The driver — a non-dimmable constant voltage unit such as the PV100 — powers the LEDs at full output when the mains is present and shuts off when it is not. This architecture has no dimming, no control wiring to the driver, and no communication protocol. It is simple, robust, and inexpensive.

Passive infrared (PIR) sensors detect the infrared radiation emitted by moving warm bodies. They are inexpensive, reliable, and widely used in corridors and restrooms, but they have limitations: they require line-of-sight to the occupant, they detect only movement (a person sitting still may be 'lost' and the lights may turn off), and their detection range and pattern vary by lens type. Microwave (doppler radar) sensors detect movement through walls and partitions, have longer range, and are less affected by temperature, but they are more prone to false triggering from moving objects outside the intended area and to interference between adjacent units. Dual-technology sensors combine PIR and microwave, requiring both to agree before switching — this reduces false triggers but adds cost and slightly reduces sensitivity. The sensor type should match the space: PIR for restrooms and small offices, microwave for warehouses and open areas, dual-tech for areas where false triggering is unacceptable.

The control device ranges from a standalone wall-mounted occupancy switch to a central time clock or building management system (BMS) contact. The simplest arrangement is a ceiling-mounted occupancy sensor with a built-in relay rated for the connected load. The relay must be rated for the inrush current of the drivers — a 100W driver can draw 15 to 25A inrush for a few milliseconds — so a relay rated for 16A or higher is recommended even for a 5A steady-state load. Multiple sensors can be wired in parallel to cover a large space, and a photocell can be added for daylight response, switching the lights off when ambient light is sufficient. For scheduled operation, a time clock or the building's existing control system operates a contactor feeding a group of drivers. The key principle is that the control device operates the mains supply to the driver; it does not communicate with the driver at all.

Latching relays deserve attention. If the relay is powered from the same circuit it switches, a power failure de-energizes it and lights may stay off after power returns — acceptable only where emergency lighting covers egress. A latching relay maintains state after power loss, so lights return to their previous state; most systems fail to the lights-on state for safety. The sensor time delay should avoid nuisance switching — too short and lights flicker, too long and savings are lost; 5 to 15 minutes is typical for offices and corridors.

The advantages of this simple architecture are practical. No dimming compatibility issues, no control bus to commission, no address assignment, no firmware updates, no flicker from incompatible dimmers. The driver is a standard non-dimmable unit, interchangeable with any other non-dimmable driver of the same rating. Maintenance is straightforward — a failed sensor is replaced by any electrician with no programming. The energy savings from occupancy control alone are typically 30 to 60 percent in intermittently occupied spaces, and the system cost is a fraction of a dimmable smart system. For the many commercial spaces that do not need light-level variation, the simplest smart lighting is also the most reliable.