Sensor lighting systems and their limitations

A simple lighting system in the past consisted of an overhead lamp turned on and off by a wall switch. Nowadays you could easily into a room and find no switches at all. How do you turn on the light? Actually, by the time you consider that question, you may find that the light has already come on for you. And when you leave, the light will automatically go off a little while after you exit the room.

Increasingly sensors are being used as the primary trigger for lighting devices. These sensors were originally for security purposes, such as to trigger an intruder light in the porch, or to start a recording device. But as with all technological things, the lifespan of such things is lengthened when more uses are found for them, so it is no surprise that these systems, which consist of a motion detector, an electronic control unit, and a controllable switch (relay), have made their way into interior lighting.

How do these light sensors work? A motion detector detects movement, and sends a appropriate signal to the control unit to close the circuit, which would allow light to come on. If there is no activity after a period of time, the circuit is opened again until movement is detected.

The detection of an occupant in the initial entry to trigger the lighting easy, it is similar to entering the field of view of a PIR detector. But how do detectors know when a person has left the room, or is sitting still in the settee?

Imagine if someone has entered the room to read, fallen on the settee, and woken up in complete darkness!

Another problem that current sensor lighting systems cannot solve is that if the delay between the circuit reset is too long, then if you are entering a room for only ten seconds to retrieve an item, then light and energy are wasted while the circuit remains closed before it resets again.

The current technology is being enhanced in all areas, including cost reduction by maximising the efficiency and lifespan of parts, as well as the increased capability to detect occupancy by means other than movement, so that if you are still for a while, the unit is aware of your presence despite your lack of movement.

Some current products being trialled include heat sensing technology, but it may be awhile before improvements in technology lower the cost to a level acceptable enough to be implemented in household units. But even then, these heat sensing units may not even address the problem. What if you are ready to fall asleep and the unit refuses to let you turn the light off? Another kind of sensor being trialled is one that gradually lowers the lighting level in the room if it senses no movement. But it would require the use of dimmable bulbs, instead of energy saving ones.

Sensor controlled lighting was implemented so that lights would not be left on overnight and waste electricity. But there are still improvements to be made. But perhaps it may be fair to say that instead of relying on automation, everyone should just make the effort to make sure energy is not wasted. It appears that the more advanced the technology is, the more it has been designed to make us stop taking responsibility for ourselves.