Skip to Content

How Does a Touchless Faucet Work?

Collage of illustrations on how a touchless faucet works.

Touchless faucets are becoming common, especially in restaurants, public restrooms, and homes. Once you figure out that this faucet does not work manually, it can be frustrating to get it to work. A better understanding surrounding the design and mechanics will help you the next time you encounter a touchless faucet.

Faucet Sensor Picks up Movement

How Does a Touchless Faucet Work - Faucet Sensor Picks up Movement

You will first notice that the front of the faucet has a sensor. To better understand how an automatic sink works, do not think of it as a machine but more as if it is a person. The sensor must pick up movement, like when your eye picks up movement, and your body responds.

Faucet Sensor Works Similar to a Human Eye

How Does a Touchless Faucet Work - Faucet Sensor Works Similar to a Human Eye

Inside the faucet are the mechanics that open and close the water stream, let’s call that the brain and the sensor activate the mechanics to open a value to let the water through. Think of the sensor like an eyeball; when hands are in front of the eye, and the lights overhead bounce light off the hands, the light projects an image that the eye registers. Light bouncing off your hands to the sensor has the same effect.

Chat Box

Home Expert (Bot)
Hello, how are you? Ask me anything about interior design, home improvement, home decor, real estate, gardening and furniture.

Faucet Sensor Picks up Light Signals

How Does a Touchless Faucet Work - Faucet Sensor Picks up Light Signals

When the light reflects off your hands into your eye, it takes that light and turns it into a signal that your brain interprets and responds to accordingly. The same happens with a touchless faucet. The sensor is the eye of the faucet, and when the light bounces off your hand, it sends a signal to the brain of the faucet, in this case, the valve that opens to let the water through.

Different Lights That Could Activate the Faucet Sensor

How Does a Touchless Faucet Work - Different Lights That Could Activate the Faucet Sensor

The sensor is designed to pick up that your hand is close to the faucet and activate the water valve. But what exactly does the sensor look for, and how does it work?

To better understand how the sensor functions, it is necessary to understand the different kinds of light. The common understanding for most people regarding light is what is known as visible light, but this is only one kind, and there are multiple kinds of light.

There are damaging types of light known as cosmic, gamma, x-rays, and ultraviolet light called short lights. Then there are longer types of light known as infrared, microwave radar, and radio, and a simple experiment will show to which kind of light the sensor responds.

The Faucet Sensor Does Not Work With Visible Light

How Does a Touchless Faucet Work - The Faucet Sensor Does Not Work With Visible Light

If the sensor works on visible light, it will not activate with the light in the room turned off. If you tried the experiment, you noticed that the sensor still picked up hand movement and activated even with the room light turned off. The sensor activating in a dark room eliminates visible light as the light source it needs.

With visible light eliminated, the next best guess would be that the sensor reacts to infrared light. Infrared light exists in two general types known as heat infrared and near-infrared. Another small experiment can identify which infrared light the sensor responds to.

Heat Infrared Does Not Activate the Faucet Sensor

How Does a Touchless Faucet Work - Heat Infrared Does Not Activate the Faucet Sensor

Heat infrared picks up a thermal image, and if the sensor works with heat infrared, it will activate because of the body heat in your hands. Sliding something that does not give off heat, like a notepad in front of the sensor, will indicate if heat activates the sensor. The notepad activated the sensor, and this means that the sensor does not respond to heat infrared light.

Faucet Sensor Responds to Near-Infrared

How Does a Touchless Faucet Work - Faucet Sensor Responds to Near-Infrared

The second alternative to infrared is near-infrared, used in TV remotes as one example. Digital cameras can see near-infrared, and if you push a button on the remote while pointing it at the camera, you will see a purplish flashing light. This flashing purplish lite you see through the digital camera is near-infrared light.

Some cell phone cameras use a near-infrared laser to autofocus, and you can identify it on your phone as a purple dot close to the phone’s camera lens. Covering up the autofocus laser and pointing it at the sensor, the sink will not activate. As soon as the obstruction is taken away from the autofocus laser and it connects with the sensor, the sink activates.

Going back to the example that the sensor works like the human eye would mean that instead of looking for the reflection of visible light, the sensor is looking for a near-infrared light reflection. The sensor has near-infrared light that points at our hands and looks for the reflection of that near-infrared light.

Faucet Sensor Activates Within Parameters

How Does a Touchless Faucet Work - Faucet Sensor Activates Within Parameters

Near-infrared light activates within designed parameters and needs a certain light intensity before it activates. To test the activation parameters tipping your hand from side to side to change the amount of near-infrared light the sensor picks up can indicate how much light needs to get back to the sensor. You will notice that the sensor only activates when there is enough reflection from your hands.

The faucet sensor uses near-infrared and only activates when the near-infrared light reflects from your hand, but does it matter where your hands are? As shown, hand placement is important and having it directly in front of the sensor is the best place to hold it to activate the faucet.

Hand Location to Activate Faucet Sensor

How Does a Touchless Faucet Work - Hand Location to Activate Faucet Sensor

Knowing that you need to hold your hand right in front of the sensor to activate it could be problematic, especially if you have a long sleeve shirt and do not want water all over it. Touchless faucets do not need your hands right up against the sensor but only in front of it and will activate at a distance of one inch. Holding a notepad one inch away shows that the sensor activates.

Faucet Sensor Activates Between One and Twelve Inches

How Does a Touchless Faucet Work - Faucet Sensor Activates Between One and Twelve Inches

Starting at one inch and moving the notepad away from the sensor inch by inch, the water flow continues until the notepad is twelve inches away and stops. The design of the automated sink is to provide a flow of water within the diameter of the sink bowl. When the light reflection exceeds the parameters, the sensor signals the water valve to close and for the water flow to stop.

The sensor will only activate if it picks up that your hands are in the sink bowl area and will shut the water flow when not in the sink bowl to prevent water wastage.

Faucet Sensor Reaction Time

How Does a Touchless Faucet Work - Faucet Sensor Reaction Time

With your hands placed in front of the sensor, the light bounces, and the sensor signals the valve to open. Once the signal is received from the sensor, the valve activates, and the water starts to flow. So how long does it take from the time the sensor relieves the light and sends the signal to the valve until the water starts to flow?

Only when there is enough light, for long enough, does the water turn on. A recording with a time-stamp on to slow the video down to a frame-by-frame speed shows exactly how long it takes from when a hand is in front of the sensor until the water turns on. It takes between 21 and 22 frames, roughly one second, for the sink to turn on.

For the best result, put your hand in front of the sensor to get the most near-infrared light reflected and leave your hand there for one second to get the water flowing. If your hand is positioned correctly and you waited for a second, and there is no water, the touchless faucet is likely faulty, and you should use another faucet.

Resources:

How do automatic sinks work?

Chat Box

Home Expert (Bot)
Hello, how are you? Ask me anything about interior design, home improvement, home decor, real estate, gardening and furniture.