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In this time of social distancing to prevent the spread of the Covid Virus there is a smartphone app ( that will track if you get too close to other people.  I've been playing with time-of-flight sensors which do a decent job of measuring distances and I thought that I would come up with a simple wearable circuit that would provide a visual alert (possibly also audible) when someone is closer than 6 feet which is the prescribed social distancing separation.


The advantage of a simple circuit is that it wouldn't require an app or Bluetooth and it would give you immediate feedback.  There are a number of issues with using a TOF ranging sensor so it would only be useful in a limited set of scenarios.


Here are some of the issues:

  1. Uni-directional, i.e. only ranges in the direction that it's pointed
  2. Limited range - VL53L0X 2 meters, VL53L1X 4 meters
  3. Does not discriminate human beings - will detect any object
  4. Range could be reduced in bright light (sunlight)


I am pretty much designing for a specific scenario that would solve the primary outdoor social distancing problem that I have.  My wife and I have gotten used to staying indoors at home most of the time.  The primary exception is walking the dog daily.  The dog likes to walk 3-5 miles a day, rain or shine.  And she's a Beagle so she has to smell everything therefore walks take us 1-2 hours.  The paths in our neighborhood are nominally 3-4 feet wide so if we encounter other people the protocol is for one party to step aside and yield the path.  That works if you see people before they enter your 6 foot isolation zone.  The main problem is people coming up quickly behind you and not yielding the appropriate space (mainly runners and children).  So, I'd like something to alert me when someone is approaching from behind as I'm often distracted by the dog and don't hear them.  This sensor wouldn't be practical indoors other than  to demonstrate appropriate social distance.


I currently only have a VL53L0X so I'll need to get a VL53L1X as the 4 meter range is probably more appropriate for this application.



For the microcontroller I'd like to use an Adafruit Flora: FLORA-Wearable-electronic-platform-Arduino-compatible.  The Flora is small - 1.75" diameter, capable of battery operation, and has an onboard NeoPixel LED that can be used for visual alerts.  It is programmable using the Arduino IDE and has the I2C pins required for the TOF sensor..

Adafruit FLORA


I don't have a FLORA so I'll have to order one but it shouldn't take long to set this up when I get it.  And I'll need to print a couple of cases (FLORA needs to be visible in front and sensor in back).  Might make sense to add an audible alert.  I'll need to think about what to use for that.