How to best detect presence within max 150 cm?

Hi everyone,

We have been working on a project for the last year and we simply can't get one of the main functionalities quite right. We are developing a little bot to be placed on top of a desk, which has to detect presence of a person within max. 150 cm. The bot is placed in an office environment, so it's important it does not detect presence of people at other desks. We have tried a variety of sensors and do currently use a IR thermometer from MLX (Like this one), but we are not fully satisfied as it's very dependent on the direction and a bit pricey. We are now looking at microwave radar sensor modules, but the range seems a bit too long. Do you guys have any other good ideas?

Best regards Mads and the team :slight_smile:

We have also tried the following sensors:

  1. PIR sensor. Too long a range. Do not look like it's possible to limit it.
  2. IR and US proximity sensors. Too many false readings. Very dependent on direction and the user's clothing.
  3. Bluetooth modules. Too inaccurate.

We have read most of the other topics on this matter, but could not find the answer to our questions. So we do very much hope you can help us out :slight_smile:

Try the various time of flight sensors such as this one.

It has a ~30 degree detection cone so it'll need a clear view of the person without any obstructions in the peripheral zone.

mikb55:
Try the various time of flight sensors such as this one.
Adafruit VL53L0X Time of Flight Distance Sensor - ~30 to 1000mm : ID 3317 : $14.95 : Adafruit Industries, Unique & fun DIY electronics and kits
It has a ~30 degree detection cone so it'll need a clear view of the person without any obstructions in the peripheral zone.

mikb55 - thanks a lot :slight_smile: Do you have any experience using this sensor to detect presence?

They measure distance therefore:

  • Close = present.
  • Far away, or out of range = not present.

You choose what distance to use as the threshold.

I've used the VL53L0X version which does up to 2m.
It depends on the reflection of infrared light, so the type of clothing worn by the people will affect the maximum detection distance.

Thanks - I'll give it a shot :slight_smile: