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If you own an Amazon Echo smart speaker, then you already know it’s listening, waiting to be called on like a Labrador retriever. Once it hears that wake word from you, “Alexa, play ‘Funkytown,’” it springs to action.
But did you know that many Echo speakers have a hidden power you can put to use? With built-in ultrasonic detecting abilities, your Echo can do more than just respond to questions. It can act like a smart motion sensor and perform tasks such as turning on lights or air conditioning, as well as alerting you to intruders, without your having to buy extra sensors that take up space and burn through batteries.
If you have a 4th-gen Echo or Echo Dot or a 5th-gen Echo Dot, you’re all set. Ultrasonic sensing isn’t available on older Echos or any Echo Show display (they have camera-based motion sensing), nor is it on the new Echo Pop. Although some third-party Alexa-enabled speakers may include features such as better audio, weatherproof ratings, or rechargeable batteries, only Amazon Echo speakers include this additional capability.
It sounds good for its size, responds quickly to voice commands, and includes all the Alexa features including ultrasonic motion sensing.
Echo speakers use ultrasonic sound waves to detect motion, similarly to how a bat uses sonar to find insects. When enabled in the Alexa app settings, the Echo continuously emits sound waves that are imperceptible to humans. Your speaker then uses its built-in microphone to monitor changes in how the waves bounce back to it, which happens when the waves encounter something moving, like you.
Using Alexa Routines (Alexa-speak for a simple command program), also found in the Alexa app, you can trigger actions when the speaker detects the presence of someone in the room. You can also adjust the sensor’s sensitivity and range in the Alexa app.
Separate infrared motion sensors such as these can be set up to do the same thing, but if you have a compatible Echo, you may not need the additional sensors.
One nice benefit of Echo’s ultrasonic ability is that it continues to work even while the same device is streaming audio, so you don’t need to pause your music. Also, it doesn’t create any light like some infrared sensors do, and it doesn’t detect through drywall, so it won’t accidentally react to sounds or motions from an adjacent room.
In addition to ultrasonic motion detection, select Echos can be instructed to monitor for specific sounds, including the beeping of smoke or carbon monoxide detectors, barking dogs, breaking glass, snoring, or a baby crying. All of these functions can be turned on or off in the Alexa app.
If you have smart bulbs, or lights connected by a smart plug or switch integrated with Alexa, you can easily set up a Routine that turns the lights on when someone enters and stays in the room. This can be especially helpful when going into dark basements or garages where the light switch may be out of the way, such as a cord hanging from a bulb in the middle of the room. Our tests found that Alexa’s ultrasonic sensor isn’t quite as fast as other infrared motion sensors we’ve tested, including the Philips Hue sensor. Our Echos took about four seconds to turn the lights on, while our Hue sensor was almost immediate. However we found it was fast enough and very reliable.
Fans and air conditioners are great for cooling down a room on a hot day, but leaving them on when no one is in the room wastes a lot of energy. If you connect your fan or AC unit to an Alexa-compatible smart plug (like one of these), your Echo can turn it on automatically and keep it on when people are in the room. If your window air conditioner is Alexa-compatible, then you can do the same thing without the smart plug.
If you like to get your news in the morning while brewing your coffee, Alexa can automatically deliver a salutation and give you a news brief or stream a podcast or a playlist as soon as it detects a person moving in the kitchen. For this Routine, you need to also specify a time frame (such as between 6 a.m. and 7 a.m.), otherwise you’ll keep triggering this action all day long.
Like a motion sensor for a security system, Echo’s ultrasonic sensor can listen for intruders. If someone enters a room when no one is supposed to be home, you can have Alexa send an alert to your phone, play a sound or message, make a phone call, or trigger a smart device—perhaps turn on all the home’s lights. To test it out I set up a Routine to send an alert when someone entered my office. It works reliably, but with some caveats.
Though Echo’s listening skills and ultrasonic sensors are effective in turning things on, they’re less effective at turning things off as quickly. The feature can determine when someone enters a space, but it takes about 30 minutes of no motion for the speakers to realize no one is in a room and then trigger the off Routine. This means if you leave a room and there’s no more motion to detect, the lights or fans may stay on for another 30 minutes. Another issue is if you’re in a room that’s large enough, you may be out of range of the sensors, which could cause the speaker to believe the room is empty and turn off the connected device. This would happen sometimes in my basement gym where the Echo Dot would sense me entering through the door and turn on the lights but not be able to detect me once I moved 25 feet to the other side of the room.
A similar problem happens if you’re using an Echo to alert you of motion. You may receive an alert that someone has entered a room, but because of the delay you won’t know if they leave and another person enters shortly after. In this case it’s a useful but not always reliable way to know if people are in a given space.
And unlike some security cameras, ultrasonic sensing can’t distinguish between people and pets. My dog triggers my office Routine all day long.
This article was edited by Jon Chase.
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