HiLetgo5pcs HC-SR04 Ultrasonic Sensor Distance Module for Arduino UNO MEGA2560 Nano

Works perfectly fine.

The media could not be loaded.  Arrived at the door the day after ordering! No messing about or delays.These sensors are excellent value for money, 5pcs for $9, bubble wrapped for safe shipping.A project was built in around 10 minutes to make use of one, as seen in the attached video. There are plenty of libraries for Arduino use and they work as described. Detection range has been measured up to 10ft for tiny movements.These are sure to end up in robot line follower projects, maybe a mosquito repeller circuit (I so hope so!) and a screen based range finder. They would also suit home security projects.

This is a pretty standard part, but there are places where companies could cut corners. HiLetgo did not do that here. These are quality parts that are reliable and simply work as expected.The five-pack is great for when you want to build something that can measure its clearance on all sides or when you want to build more than one project that needs the ultrasonic distance sensor.These sensors are part of a class that I'm teaching, and I know I will not have to worry about hardware issues for my students when they use these parts.

In my tests, clutter was a much more difficult problem than I was anticipating.I expected that enough of the mass of the signal would be going straight out and coming straight back that it would dominate and overwhelm any sideways components, making this effectively "range to the thing you are pointing at." Unfortunately that is not the case. This will pick up objects from just about 90 to 120 degrees off center line, which is HUGE in comparison to my expectation.Put in other words, If you were to set this on the long side of a table, pointing across the whole surface toward a door, you would not be able to tell that the door was open or close, as the signal reflecting off the table surface would "short out" the echo. You would only get a signal that was a closer match to the sensors height off the table.I'm still investigating possible options to shape/lens the sound for a more directional measure...

I hooked these up with an ESP8266 IoT device in order to measure whether a garage door was open or closed. Works good.

Good and fast.