How Does a Dimmer Switch Work?

Stop! Don’t buy a dimmer switch without asking how does a dimmer switch work! Especially in 2019 with all hot buzz about new technology. 

Making the mistake of buying the wrong dimmer switch can cause wildly amounts of concerns, especially if you’re installing yourself. If you have questions about installing your switch give us a ring!

Background of The Dimmer Switch

Dimmer switches, as obvious, help you to reduce the brightness level in your smart home. Before installing in your home, ask the question how does a dimmer switch work?

Today, we’ll walk you through how these dimmer switches work, and we’ll try not to blindside you with science; although we’ll need to get slightly technical!

We’ll also give you a brief snapshot of 4 of the most effective dimmers on the market so you can enjoy remote control of your lighting without needing to keep jumping out of your seat.

Before we get into the nuts and bolts of dimmers, where did this concept originate? And bear with us because this is more than a history lesson. Seeing how dimmer switches used to work will help you better understand how they function today.

History of Dimmers

Why do I need to know the history of dimmers? 

It starts here, different homes require different wiring. If you want to understand the basic complexity of how a dimmer switch works; know the background!

The early dimmers

Early dimmers were controlled by physically adjusting bulky dimmer panels. While this was straightforward, it also meant all power needed to come straight through the lighting control location. This was inconvenient, inefficient, and potentially dangerous.

With these old dimmers, a variable resistor was used. Resistors don’t conduct electricity effectively since they offer so much resistance to the moving electrical charge. Variable resistors have a bit of resistive material, and a pair of contact arms, one stationary and one moving. Total resistance is varied by manipulating the distance the electrical charge needs to travel through the resistive material.

So far, so good?

Energy is lost via heat as the charge works its way through the resistor. By adding a resistor into a series circuit, the energy consumption leads to a voltage drop so there’s less energy available for other loads such as the light bulb. This, in turn, leads to the bulb’s light output dipping.

By 1959, the founder of Lutron came up with a dimmer that used a diode and autotransformer. Not only did this save even more energy, it was also ideal for installation in a regular electrical wall box.

The problem here is that so much energy is wasted simply to heat the resistor. Not only is this remarkably inefficient, it’s also dangerous due to the amount of heat generated.

A safety dimmer was patented in 1896 leading to less energy wastage and the modern dimmer switches you find today use a different approach. Are you still asking how does a dimmer switch work?

The Basic Principles of How a Dimmer Switch Works

Diverting energy from the bulb into a resistor, as we’ve explained, is not the best method of dimming lights. It works, but there’s a superior way…

Modern resistors function by quickly switching the light circuit on then off. Using this approach, the total amount of electricity traveling through the circuit is reduced.

This switching cycle is based on the way household AC current (alternating current) fluctuates. AC current has a varying voltage polarity on a sine wave. A sine wave is a curve and with AC current, the voltage undulates between positive and negative. To strip that down even further, you can just think of the current changing direction.

In the US, a single cycle takes place 60 times a second. This is expressed as 60 Hertz.

With a dimmer switch, this regular sine wave or curve is chopped up deliberately. When the current changes direction, the light bulb circuit is automatically shut off. The change in direction takes place when there’s zero voltage which happens twice in every cycle (120 times per second). As soon as the voltage hikes back to a certain level again, the light circuit comes back on.

So why do we say a “certain level” rather than being more specific?

Well, this depends on where you’ve positioned the knob or the slider on your dimmer. When it’s on its brightest setting, the circuit switches on very shortly after it cuts off. Since the circuit is switched on for the bulk of the cycle, more energy per second is given to the light bulb.

How about when the dimmer is set lower? As you’d expect, the circuit won’t go back on until later in the cycle.

Where in the past a rheostat redirected the flow of current, the knob or slider on a modern dimmer acts a variable resistor but performs as a signal rather than redirecting flow. Modern dimmer controls using the above method are over 99% efficient meaning less than 1 watt of energy is wasted when controlling a 100-watt bulb. Also, unlike the earlier method we described, you don’t get all that unwanted heat, either.

A quick aside: although bulbs last much longer with modern dimmers and there’s minimal wastage, output per watt from the bulb could still be improved.

How Does a Dimmer Switch Work?

You might be wondering how the flow of electricity is restricted to achieve this and that’s all down to the use of a TRIAC (triode AC switch).

A TRIAC is a semiconductor device a bit like a transistor constructed from multiple layers of semiconductor material, N-type (this has free electrons) and P-type (this has holes where these electrons can go).

A TRIAC has 2 terminals wired into either end of the circuit. There’s a voltage difference that changes as the alternating current fluctuates. The upper and lower terminal switch between being positively charged and negatively charged accordingly.

There’s a gate wired into the circuit via a variable resistor.

In effect, the TRIAC works as a voltage-driven switch. The switching action is controlled by the voltage on the gate. The voltage on the gate is controlled by the variable resistor.

We hope you’re still with us!

With normal voltage across the terminals and very little voltage on the gate, the TRIAC acts as an open switch conducting no electricity. If the TRIAC is to conduct electricity between the 2 terminals, it requires a boost in voltage on the gate. A variable resistor comes into play to achieve this…

When current travels through the resistor, a firing capacitor is charged until it has enough voltage so the current can be conducted down to the lower terminal. Total resistance can be increased or decreased by moving the dimmer knob which in turn shifts a contact arm.

With the dimmer knob turned to dim, greater resistance is offered while turning the knob in the other direction lowers resistance. When the current hits zero voltage again, the cycle then continues.

While this method works well, the only real downside is that buzzing noise distinct to dimmers that can be extremely annoying. More expensive dimmer switches add components to counter this buzzing and high-end dimmers used outside residential settings – with stage lighting, for example – use an autotransformer instead of a TRIAC to sidestep this issue completely.

So, whatever the variations, dimmer switches today operate on the same principle: they chop up AC current so the total energy powering the light bulb is reduced.

Why Use a Dimmer Switch?

Now you’ve seen how dimmer switches work, why should you bother using one in the first place?

The obvious motivator is varying the light in a room you use for multiple purposes…

In the living room, you can set the mood for intimate entertaining with guests by lowering the light then ramp it up when you need a bit of brightness for board games with the kids.

When it’s time for your children to go to bed, you can dim the lights in their rooms to ease them towards dreamland. First thing in the morning, you can ensure there’s plenty of light for them to start their days energized.

In the bathroom, use dim light when you want to relax in the tub then amp it up when you need to shave or do your makeup.

Beyond mood lighting, you can also save money on your electricity bill. Dimming a light by 25% can yield savings up to 20% while dimming it by half can slash consumption by 40% translating into worthwhile reductions month in, month out.

With less strain on bulbs, these will last longer giving you secondary savings that might seem negligible but can mount over time.

Can You Use Dimmer Switches With Any Lights?

The best bulbs to use with dimmer switches are halogen bulbs and incandescent bulbs.

Using these bulbs, not only do you get an affordable lighting solution, you can dim the brightness from 0 through 100%. A standard incandescent dimmer is all that’s required.

The drawback with LED bulbs and fluorescent bulbs is that light levels can only be dimmed to around 20% of maximum brightness. Also, due to power demands, these bulbs don’t work with TRIACs.

So does that mean that using a dimmer with LEDs or fluorescent bulbs is entirely out of the question?

No!

A CL dimmer uses resistors to alter the power output and you will be able to use your bulb of choice, even if that’s an LED or fluorescent light. You do need to make sure the lights themselves are dimmable. If you attempt to use an incandescent dimmer with these lights, it will either not work at all or malfunction.

We’ll highlight some dimmers that allow you to use LEDs so don’t worry if you’ve converted to this energy-efficient lighting and you want to continue using it while also ratcheting down the brightness with a dimmer.

Before we get to those dimmer switches, what about the specific types of dimmer switches?

Single-Pole: A single-pole is specifically designed for fixtures controlled by just one dimmer. This means the dimmer will act as the only switch for both turning your lights on or off and also dimming them
3-Way or 4-Way: If you’ve got multiple on and off switches for lighting, you’ll need a 3-way or 4-way dimmer
Multi-Location: Multi-companion dimmers call for multi-location dimmer switches. This allows you to exercise full control over brightness from multiple locations
Plug-In: If you’ve got table and floor lamps, you’ll need a plug-in dimmer. Most of these work with all types of bulbs including LEDs and CFLs

OK…

Now you’ve got a solid overview of how dimmer switches work and why you should consider using one, we’ll round out on a more practical note with a brief glimpse at 3 of the best modern dimmers suitable for any respectable smart home…

4 of The Best Dimmer Switches 2019

Insteon Dimmer Switch

If you’re hunting for a wall switch you’ll be able to control remotely from almost any smart device in your connected home Insteon’s classic Remote Control Dimmer Switch is a must. You’ll be able to use your smartphone or any Insteon device as a controller for great flexibility.

This switch works with any regular paddle wall plates but this is not included. Insteon offers some great and extremely inexpensive screwless plates, though. Installation is straightforward and there’s no need for a neutral wire so this smart switch is a wise bet if you’ve got an older home lacking this C-wire.

You can choose whether or not to invest in an Insteon Hub depending on what you want from your dimmer. If you don’t want to spend extra, you’ll need to set up a virtual 3-way circuit to pair your dimmer switch with a keypad or a motion sensor or even another Insteon switch.

That hub comes into its own if you want to build out a more ambitious connected home, though. You can also take advantage of using Alexa or Google Assistant for voice control as long as you have an enabled device and the hub. If you want to use Siri, you’ll need the Insteon Hub for HomeKit.

Control is a breeze whether you use voice commands or your smartphone. With the latter, a single tap allows you to control multiple devices with Scenes. You’ll be able to schedule either individual switches or groups of switches, too. You can link switches to other Insteon devices from sensors to plug-ins giving you an incredibly versatile dimmer at a pocket-friendly price.

Benefits

  • No C-wire required so perfect for almost all homes
  • Use voice commands using Alexa or Google Assistant with an Insteon hub or if nou prefer Siri, invest in an Insteon Hub for HomeKit
  • Fully customizable paddles and you can even add etched text for a personal touch

Wemo WiFi Smart Dimmer Switch

If you want a smart version of a dimmer switch, this Wemo dimmer lets you get straight down to business regulating the brightness of just about any bulb with no need for a hub.

One thing to be clear about is that you will need a C-wire, also known as a neutral wire, so make sure that’s in place before committing to purchase.

You’ll get a streamlined experience when you’re at home so you can dim your lights in-app on your smartphone or using voice control with both Google Home and Alexa. Scheduling is a breeze using the intuitive Wemo app and you can create a range of IFTTT recipes if you want even more automation. Simply pressing and holding the dimmer allows you to control multiple Wemo devices at the push of a button.

This dimmer works well with Nest’s Learning Thermostat and Nest can communicate with your dimmer to let it know when you’re away from home. Your lights can stay off when you’re away to save energy but come on randomly to make it seem like there’s someone at home.

For a great modern take on the classic dimmer switch, the Wemo WiFi Smart Dimmer Switch is a must for any connected home in 2019.

Benefits

• No hub needed with dimmer connecting directly to your home WiFi network, but this almost means you might see lapses in speed
• Works well with all compatible bulbs including LEDs and CFLs
• Use Away mode for robust security when you’re not at home with the lights coming on and off randomly

SkylinkHome 3-Way On/Off Dimmer Switch

Everyone has different needs with dimmer switches and Skylink’s 3-way on/off switch is a first-rate solution if you’ve got multiple switches. Unlike the Wemo, you won’t need a C-wire in place. Although this requires installation, it’s not complex.

One downside of this dimmer is that, while you can use CFLs, incandescent bulbs and tungsten bulbs, it doesn’t make a good fit with LEDs. It works with light loads and appliance loads up to 300 watts.

The durable lithium battery kicks out a great signal and you can build things out with multiple controllers, transmitters and sensors so it’s great for anyone with more ambitious smart home needs.

The operation couldn’t be much easier. All you need to do is press on the decorative cover to turn your lights on or off and hold it down when you want to increase or reduce the brightness.

If you’re looking to add a user-friendly dimmer switch without the call for any extra wiring, check out this Skylink kit and pop it in your bedroom or hallway or even out in the garage. You’ll be able to turn your lights on and off or dim them from both locations fuss-free so what are you waiting for?

Benefits

• Super-simple installation with no neutral wire needed
• Slots over your existing switch with a decorative cover to maintain the clean lines of your smart home
• Robust range of up to 500 feet assuming no barriers

iDevices Dimmer Switch

With no need for a hub and full support for Alexa, Siri and Google Assistant, you’ll get a fully flexible experience with this iDevices dimmer. This makes it a perfect solution for slotting into almost any smart home ecosystem.

Although installation is pretty simple, like any dimmer, there’s a lot of room taken up in the wall and you’ll need to strongarm everything back in once you’ve spliced it into your existing wiring. This switch supports both single-pole and 3-way or 4-way configurations.

If you’re invested into HomeKit, iDevices is configured for that, too.

The classic rocker design of the switch allows you to tap/hold or click/release for dimming and brightening. Double-tapping takes you instantly to full brightness or switches them off.

A nice extra is the LED light that works like a makeshift nightlight. You can even tweak the color and brightness of this in-app in true smart home style.

The app is a pleasure to use and you can create Scenes or schedule with ease.

For a great modern take on the dimmer switch that works brilliantly straight out the box with minimal fuss, we can’t recommend the iDevices Dimmer strongly enough.

Benefits

• Turn a regular switch into a fully smartened up dimmer
• Control lights throughout your home in-app on your iOS or Android phone
• Use your favorite digital assistant to customize brightness levels with voice commands

Final Word

Well, with any luck you’ve now got a solid overview of the science behind dimmer switches and an idea of which might work best in your smart home.

For next steps check out the echo dot setup and synch your dimmer switch to control with your voice and WOW your guests. There is a perfect installation and pairing guide in there.

Come back soon as we’ve got more lighting guides up our sleeve and we’re constantly updating smart home news to bring you the very best in smart home tech and how these products actually work.