There you are…getting ready to leave the supermarket. Your hands are full of bags of groceries. You get to the door. How in the world are you going to open it with your hands full? Just when you're wondering whether you'll need to set some bags down, the doors open with a “Swoosh!" as if by magic!
What's going on here? Is something supernatural at work? Is there a ghost standing nearby opening the doors for people leaving the supermarket? Nope! Would you believe it's pure science and technology?
It's true. Those doors — known as automatic doors — open and close with the help of simple technology, not magic. But they are fun and do seem just a little bit magical. If you want to pretend they're magic, we won't tell anyone!
Automatic doors operate with the help of sensors. Sensors do exactly what they sound like they'd do: they sense things. There are many different types of sensors that can sense different types of things, such as sound, light, weight, and motion.
For example, some automatic doors operate when they're triggered by sensors that sense weight. These weight sensors might be disguised in a rubber mat in front of the door. When you step on the mat, the sensors send a signal to the automatic doors that tells them to open.
When these optic or motion sensors sense motion nearby, they trigger the automatic doors to open and then close. This is why, when you approach a set of automatic doors, they will open as soon as you get close enough to activate the sensors.
Automatic doors have many useful purposes, which is why you can find them in many different types of locations. From supermarkets to airports and many types of large buildings, automatic doors make it easier for people to get into and out of buildings. They are especially helpful for people who are handicapped.
Similar to revolving doors, automatic doors also help to save energy, since they limit the amount of time that doors are open to only those times people are entering or exiting a building. And if you've ever shopped until your hands are full of bags, you know how handy automatic doors can be when it's time to head to the car!