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Everyday Engineering: Dimmer Switches

The workings behind the lowering of light

Although engineering is often associated with things like rockets and coding, there is engineering in the everyday objects around us! When I was in school as a mechanical engineering major, I had friends that had engineering internships everywhere from Gillette to Caterpillar to Nestle. Engineers are needed to plan out how things are manufactured, how food packaging is designed, the patterns of stoplights and more. In this new blog series, Everyday Engineer, we are going to be looking at the engineering behind some of the everyday objects around us.

Today: Dimmer switches

Outwardly, these handy switches may appear simple. Move them one way and the light gets brighter, move them the other way and it gets darker. However, there is more going on behind the scenes.

Old dimmer switches were made probably the way you would expect. The amount of electricity going to the light was adjusted in the switch. This was done using something called a variable resistor. This resistor would control the amount of energy that reached the light. However, it wasted a lot of electricity and created a lot of excess heat. The energy that didn’t make it to the light was turned in heat to get rid of it.

Credit: Joseph O’Connell

New dimmer switches on the other hand use a completely different technique to prevent all of that energy from being wasted. Lights controlled by dimmer switches are actually turning on off so quickly that you cannot perceive it with your naked eye. In fact, it is turning on and off about 120 times per second. The energy flow is chopped up, leading to the nickname for these switches, “chopper switches”. New dimmer switches take advantage of this by controlling how long the light stays on or off during each of those cycles. By moving a dimmer switch, you are altering the lights “turn-on value”, letting you get the exact right light level.

In orders to make these dimmers work, engineers had to create the circuitry to allow for the “turn-on value” to be adjusted and add an easy switch operating system for the user. This all has to be small enough to be easily mounted onto a wall, and cheap enough that a customer would consider purchasing it.

The longer the light stays on during each burst, the brighter the light appears to us. The shorter the light stays on, the darker it appears. This means the energy does not have to be burned off or wasted, creating a much more efficient dimmer light.

Next time you go to adjust the lights in your house, take just a moment to think about all of the hard engineering work went into it!