Motion detectors are useful smart home devices for creating simple automations, such as turning on your lights when you enter a room or being alerted to motion in your home when you’re away. Standard infrared motion detectors aren’t always the best tools for the job. There are some compelling reasons to choose mmWave sensors instead.
mmWave sensors can track multiple people
mmWave stands for millimeter wave and describes the wavelengths of the radio waves that are used by these sensors, which are small enough to be measured in millimeters. The sensors work on the same principle as radar; radio signals are sent out of the device, which reflect back off objects. The reflected signals are captured and can provide information about the distance, position, and speed of the objects that are reflecting the signals.
An mmWave sensor can send out radio waves in different directions. By measuring the angle at which the signals are reflected back to the sensor, it is possible to detect multiple objects at once. This means that a mmWave sensor can track multiple people in the same room. This is very useful for home automation; if you have two people in a room and one leaves, you don’t want the lights to turn off.
You can monitor (or exclude) zones
Since mmWave sensors can send radio signals out in different directions, it is possible to create specific zones to monitor. For example, if you have a chair in your living room with a reading lamp, you can set up a zone for that specific area of the room. You can then create an automation that will turn on the reading lamp only when presence is detected in that zone, so whenever you want to read, all you need to do is sit in the chair and the lamp will turn on.
As well as monitoring zones, you can also exclude zones from being monitored. For example, if you have some pet guinea pigs in a room, you don’t want them to constantly be triggering presence detection. You can exclude the part of the room where their enclosure is so that their presence is ignored.
mmWave sensors are more sensitive than PIR sensors
One of the most common technologies used in motion sensors is passive infrared (PIR). Our bodies emit infrared radiation in the form of heat, and PIR sensors can detect when the amount of infrared radiation increases, indicating that a person is moving within range of the PIR sensor.
For a PIR to detect motion, there needs to be a fairly significant change in the level of infrared radiation. If you’ve ever used a bathroom with a light triggered by a PIR, you’ll know that you usually end up waving your arms like a lunatic to get the lights to come back on.
In comparison, mmWave sensors can detect much smaller movements. Some mmWave sensors are even capable of detecting minimal movements such as a person breathing. This means that you can detect presence based on much smaller movements than you can with PIR sensors.
mmWave sensors can detect more
Another benefit of mmWave sensors is that they have a wide range of detection. The radio waves used in mmWave sensors have a greater effective range than PIR sensors, which rely on changes in infrared radiation.
In addition, mmWave sensors are also able to work through solid objects. For example, if you use a PIR motion sensor to control the lights in your bathroom, it will stop detecting motion when you’re in the shower with the shower curtain closed, because the curtain will block the infrared radiation from reaching the sensor. You’ll end up showering in the dark.
In comparison, the radio waves from a mmWave sensor can pass through non-conductive materials such as a shower curtain, so they can detect presence even when you’re in the shower, ensuring that the lights stay on until you leave the bathroom.
- Compatibility
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Home Assistant, Apple Home, Google Home, Alexa
- Battery life
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2-year (AAA batteries)
- Monitors
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Presence
- Range
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393 feet
Automate your smart home with SwitchBot’s affordable mmWave presence sensor. It can detect people in a room whether they’re moving or not, so it’s an ideal solution for automated bathroom lighting and other applications where people may sit still for extended periods.
You can use mmWave sensors for bed presence detection
A challenging thing to do using smart home sensors is detecting when you’re in bed. For long periods there’s usually very little movement indeed, and any movement that does occur is often underneath the covers. A standard PIR motion sensor will struggle to pick up enough motion to tell whether you’re in bed or not.
A mmWave sensor is a better solution. Since it is capable of detecting much smaller movements, it’s better at detecting when people are still in bed or if the bed is unoccupied. For the best results, it’s often recommended to install the sensor either directly above your bed or directly beneath it, since the mmWave sensor should be able to detect motion from this position, too.
You may need to combine your mmWave sensor with other triggers, such as a time-based trigger that stops the light from coming on between set hours, or a door sensor that will only detect presence when the door has been shut. There are other methods you can use for bed presence detection, such as load cells under your bed that can detect the weight change when people get in.
mmWave sensors provide more information
A PIR sensor effectively provides one piece of information; it can tell when motion is detected. This is useful for turning on a light when someone enters a room, but it doesn’t provide much information about what happens after that, other than when the motion clears.
In comparison, mmWave sensors can provide a huge amount of information that can be useful in your home automations. For example, many mmWave sensors can track multiple targets at once. Not only can you get information on how many targets have been detected, but you can also access their distance from the sensor, their relative position, and even the speed at which they’re moving.
You might not require all this information for your automations, but the more information you have available, the more you can do using your mmWave sensors. For example, if you have three people in your home, and your mmWave sensor detects three targets, you could turn off the heating to all other rooms via your smart thermostat to save using energy unnecessarily.
mmWave sensors are less intrusive than cameras
Another method of detecting presence using smart home devices is to use smart home cameras. You can analyze the feed from a camera using software that can look for motion or use facial recognition to determine if people are present.
This method can be effective, but there are some obvious problems. A major issue is that the people in your home probably don’t want cameras watching their every move. They’re unlikely to want a camera monitoring the rooms where they shower or get dressed, for example.
In addition, this method requires line of sight. If you’re in the shower, a camera can’t see you, but a mmWave sensor is still able to detect you. It won’t film you getting out of the shower, either.
mmWave sensors may be more cost-effective
In general, mmWave sensors are more expensive than PIR sensors. However, a PIR sensor on its own may not be enough to do the job that you want. For example, if you want to use a PIR in your bathroom, you may need to combine it with a door sensor. You can then create an automation that will turn on the lights only when motion is detected after the door has been closed, and won’t turn the light off again until the door has been opened. In effect, you’re using two sensors when a mmWave sensor can do the same job on its own.
Since mmWave sensors can monitor specific zones, you can also use a single mmWave sensor for multiple automations. As mentioned earlier, for example, you could use the same mmWave sensor to turn on your living room lights when you enter a room but also to turn on the reading lamp when you sit down in a specific chair.
This removes the need to get multiple sensors to do different jobs.
mmWave offers presence detection, not just motion detection
This is the biggest reason to go for mmWave sensors over PIR sensors. PIR sensors are designed to detect motion, but mmWave sensors are capable of detecting presence. These are two very different things.
A motion detector can turn on your living room light when you walk into the room, but once you’ve sat down, it has no idea whether you’re still there or not. With basic automation, the light is eventually going to turn off once the PIR stops detecting motion. You can try to work around this using more complex automation, but it’s still not going to be ideal.
In comparison, a mmWave sensor can not only detect when you enter a room, but it can also tell if you’re still there. As long as your presence continues to be detected by the mmWave sensor, the light in your living room will stay on. It’s only once you’ve left the room and presence is no longer detected that the light will turn off.
You may find that you get the optimum results by using both PIR sensors and mmWave sensors. Some PIR sensors can be a little faster to detect when you enter a room, at which point the mmWave sensor can take over monitoring your presence. You don’t need to use both, however; an mmWave sensor can do both jobs, although it may be a little slower to react.
mmWave sensors aren’t perfect, but they’re better than PIR
Presence detection is a key facet of many home automations. Having your lights automatically turn on when you enter a room can feel like magic until you’re suddenly plunged into darkness just because you’re sitting still. Standard PIR motion sensors can’t detect presence, but mmWave sensors can, meaning you’re far less likely to find the lights going out when you don’t want them to.
mmWave sensors aren’t perfect and can have issues with false positives or slow detection. You might find that a combination of PIR sensors and mmWave sensors gives you the best results. However, I use an mmWave sensor in my home office (the Everything Presence Lite) to control my lights, and I’ve found that the vast majority of the time it works exactly how I want it to.
Stephan is the sports journalist for the Maple Grove Report.
