Ever needed to detect people presence? let’s get to know the Hilink ultrasonic presence sensor, a neat little radio-waves-based human presence detection sensor, super simple to use.

According to its datasheet, it uses a 24GHz radar wave to detect moving or slightly moving bodies. For me that means that still bodies won’t be detected, but I have not tested it. Its detection range is up to 8 meters (and up to 60 degress), preferably upside down or at least horizontally.

How does it work and configurations

The most basic usage of this sensor is to connect an LED (or a microcontroller) on pin OT2, besides supplying it with 3V3 and GND. See the picture below for a reference test design. Resistor can be anything between 220 Ohm and 2k2 Ohm.

Now there is a single configuration you need to make (there are others, but are not necessary), which is the sensor detection high level time. It is the time the output will remain on after the last human presence detection; stardard value is 30 seconds. We will change that to 5 seconds: first you need to download the HLK-LD2420 Tool from here.

You are going to need a USB to Serial converter, the likes of the FT232 of the image below. Connect it like the image suggests and plug the USB into your computer.

After downloading and unzipping the software, click in “View/set param” at the top left. Select the COM port your USB to serial converter shows up at, then click “Connect”. Baud rate is 115200, no need to change.

tip: if your COM port changes you have to close and reopen the program again, it does not refresh.

Then all you have to do is change the “Absence report delay” to a value your want; I choose 5 seconds. Then at the bottom of the screen click “Set sensor config” and “Save config file”. Now my sensor will keep its output ON for only 5 seconds after the last detection.

The end result

I made a video explaining how this sensor work, below. Also if you want to buy it just click my affiliate link. If you want to know more presence sensors, also check this out.