No-Face-Touchy Training Collar (No Magnets!)

An ultrasound collar that helps the wearer break their unconscious habit of touching one's own face by blinking a warning light and beeping

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Among the CDC guidance for the prevention of spread of respiratory infections, is the advice to avoid touching your face. This is a difficult habit to break as we tend to carry out these habitual actions unconsciously. I created a simple Arduino ultrasound "wearable" to help train the wearer into breaking this mindless habit of face-touching. It uses two cheap ultrasound sensors arranged in a special configuration below that wearer's face in order to detect the approach of their hands. There is no need to place magnets anywhere on the face.

I also demonstrate one possible extension of the apparatus in which it actively intervenes in a face-touching action -- a servo mechanism inserts a sanitizing paper towel into the wearer's hand so as to minimize the infection risk in situations where touching one's face cannot be avoided (e.g. adjusting spectacles, scratching nose)

The respiratory illness pandemic in which the maker community now finds itself has initiated a wide range of projects aimed at the problem of infection control. There are projects for making Personal Protective Equipment, ventilators, track and tracing, fever detection, hand washing timers, etc. But looking over the Centers for Disease Control guidance on infection control, there seems to be a gap in coverage -- projects to stop people touching their face. There are only a handful of projects using wrist accelerometers, Bluetooth signal strength, and ultrasound earbuds -- these were researched by MIT Media Lab's project, Saving Face. There was also one famous failure that involved magnets being placed in the nose which unfortunately landed the inventor in hospital to have them removed.

My parts bin lacks the more advanced sensors that MIT Media Lab used, so this project is restricted to the cheap ultrasound sensors and an Arduino Nano that were left over from an autonomous robot project. It will also avoid having to place magnets anywhere on or near the face.

The prototype device I made is intended to be worn on the neck with the ultrasound sensors sweeping out an area just below the face. If the wearer's hand is detected approaching his/her face, the Arduino Nano issues a beep via a piezo speaker while flashing warning lights.


Added servo connections to the Arduino

svg+xml - 54.76 kB - 06/06/2020 at 17:31



Circuit connections for Arduino, ultrasound sensors, piezo buzzer, and LEDs

svg+xml - 48.24 kB - 06/06/2020 at 16:00


  • 1 × Arduino Nano (clone) Purchased from Ebay in a set of 3
  • 2 × HC-SR04 ultrasound range sensor Ebay purchase 4 years ago for a robotics project
  • 4 × Red LEDs This came from my first Arduino development kit purchased from Oomlaut
  • 1 × Piezo Transducer Purchased from Ebay for a tap sensor project I never did
  • 2 × NPN bipolar junction transistor My dad recovered these from old PCBs

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  • Sanitizing Wipe Servo Extension

    bornach06/06/2020 at 17:27 0 comments

    I was actually surprised at how well the ultrasound detection worked. It was quite difficult to sneak my hand past the alarmed region to touch my face or glasses. It should have no problem dissuading the wearer from making unconscious gestures that put their hands in contact with one's face unknowingly.  Of course, it is unpractical to were this while doing chores about the house. Moving through doorways and opening cupboards tends to trigger the alarm. It might have limited use when sitting still working on a laptop or tablet.

    I had an idea to extend the functions of the collar by adding a servo motor that thrusts a sanitizing wipe (absorbent paper with alcohol or disinfectant soap) between my hand and face:

    I made this cardboard prototype to try out this idea. It would be worn on my wrist. Two more pins on the Arduino Nano would be used:

    Pin 8 is used to turn power to the servo on and off - it only needs power when moving the sanitizing wipe into my hand or out of the way. Pin 9 connects to the servo control.

    If a training collar to stop the wearer touching their face were not already utterly ridiculous, this certainly is now!

  • Non-standard LED driver

    bornach06/06/2020 at 16:14 0 comments

    The LED driver circuit is not the recommended way one would typically control an LED array using the a microcontroller GPIO pin. The current limiting is achieved by keeping the NPN BJT (C945) in its linear region by using a 18K ohm resistor on the base. This saves us a current limiting resistor but results in more heat dissipation by the BJT.  I didn't really need to do this, but I just wanted to see if such a setup would work. Might come in handy if your parts bins lack resistors of the required value for current limiting.

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Dan Maloney wrote 06/01/2020 at 20:42 point

Heh - like the Cone of Shame for humans.

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