top of page
  • Writer's picturePuriphico

The device that tells you when your hands are clean.

I don’t know about you, but I have 2 different timers for brushing my teeth: one is built into the electronic toothbrush, and if that fails, I have the mini-hourglass (for two minutes) as a backup.

Of course, you wouldn’t be wrong to assume that countless trips to the local dentist have left me paranoid about my hygiene habits, but that is not the purpose of this article. The purpose of this article is to introduce you to my device, Puriphico, and the looming question: Why do we have methods to help ensure that we brush our teeth for 2 minutes, but no means by which we can monitor our handwashing practices - especially considering the potentially-fatal effects of improper handwashing?

This article will cover 3 questions related to my device: ‘What is a Puriphico?’, ‘Why should I wash my hands for 20 seconds?’, and ‘How does the device work?’.

What is a Puriphico?

  • A device that can detect when you are washing your hands, indicate how long you have been washing your hands, and alert you when you have sufficiently washed your hands (ie. after 20 seconds). Currently, it is the only smart, electronic device that can help you monitor your handwashing practices.

  • To use it, you would place the device adjacent to any faucet; by doing so, you can see real-time how long you have been washing your hands through LED lights accompanied by an OLED screen; when the green light flashes, you know that you have sufficiently washed your hands for 20 seconds, thereby having eradicated all harmful bacteria.

    • A simple way to envision the concept is like a toothbrush timer: most people who use a toothbrush also have some sort of timer that alerts them when they have brushed their teeth for two minutes - a widely accepted hygiene practice. Yet, despite handwashing gaining prevalence in recent months, most people do not employ accurate ways of timing their handwashing. Not only is Puriphico a simple solution to help you develop good hand-hygiene habits, but it also significantly reduces your chances of contracting a potentially life-threatening respiratory infection (such as colds, the flu, or COVID).

Why should I wash my hands for 20 seconds?

  • I feel that the following empirics summarize my points nicely:

    • Improper handwashing (ie washing your hands for fewer than 20 seconds) is responsible for:

      • 21% of all respiratory infections (including colds, the flu, and, most recently, Coronavirus) contracted annually.

      • 1 million deaths each year and reduce diarrheal-associated deaths by up to 40%.

How does it work?

  • I know that here, on Hacker News, many of you are mostly interested in the tech, so here you go :)

    • Puriphico uses a Keyestudio Passive Infrared (PIR) motion sensor coupled with a calibrated microphone to detect when someone is washing their hands. When I say ‘calibrated microphone,’ I mean that the audio input can be calibrated to recognize the sound of hand-scrubbing with soap (a vastly different frequency pattern than regular running water, providing the opportunity to deploy a device capable of recognizing auditory + visual inputs associated with handwashing).

    • The device uses an Arduino Nano 33 BLE Sense microcontroller (though the code has not yet been published), incorporating a OLED screen that displays how long you have been washing your hands real-time (when not doing that, the screen displays the percentage of times you washed your hands for the full 20 seconds). In addition, it features two 5-mm LED lights that give you various visual cues as you wash your hands (described above).

If you like the hack, I encourage you to share this article with a friend! You can follow my social media pages (@puriphico on Instagram and YouTube) and subscribe to my website ( to follow the updates of the device’s development.

If you want to build your very own Puriphico prototype and learn the intricacies of circuit design and embedded systems, I’ve got you covered - check out the Build-Your-Own page on my website here.

56 views0 comments


bottom of page