Kill COVID: 20 second hand wash sensor (no soldering needed)

Washing your hands is a highly effective way to reduce the spread of viruses and bacteria. This has been highlighted by the ongoing COVID-19 Corona virus pandemic and the current protective recommendations.

To be effective, a hand wash should be at least 20 seconds long.

But 20 seconds is a long time. Longer than most are used to washing their hands.

This is why we built this hand wash tracker: to help us hit that 20 second mark.

The hand was sensor uses only off-the-shelf hardware – we use the LPSTK kit from Texas Instruments (we pronounce it lipstick) – and neither soldering nor programming is needed to try it out.

How it works

The hand wash sensor uses light to detect if a person standing in front of it. Then it starts to blink:

• A red blink for 20 seconds to indicate that we should keep washing
• A quick green blink to indicate that we are done

The hand wash sensor also keeps checking if the person still is standing in front of it.

The sensor measures the total time that the person was detected to be in front of the sink and sends this data through the wireless all-IP mesh network created by each sensor to a backend database.

We can then use a HTML5/JS frontend to display the data, like this:

How to set it up

The sensor is easy to install at a sink: simply place it by the sink with the openings in the red cover facing the sink.

The LPSTK can also be attached to the tiles with double-sided tape or similar.

The light sensor is placed in the left opening and it learns the light conditions in the room as it is deployed.

The LEDs are placed in the right opening and it will begin blinking when it detects a person washing their hands.

Setting up the hardware

To set up the hardware, we need at least one LPSTK and a Launchpad board. They can be purchased as a bundle from Texas Instruments.

The Launchpad board is used to program the LPSTK and is also used as an access point for the wireless network.

To program the LPSTK, first install the Uniflash software from TI, then download the LPSTK firmware file from here. Connect the LPSTK and the Launchpad with the JTAG cable. Be sure to disconnect all the jumpers on the Launchpad so that the Uniflash won't install the firmware on the Launchpad board.

The LPSTK is now ready to be used as a hand wash sensor.

To connect it to the wireless network, install the Launchpad as a wireless access point with a Raspberry Pi. Follow the instructions on how to set up the Raspberry Pi and the wireless network by following the instructions from this project. Download the necessary firmware files for the CC1352R1 Launchpad here.

Now wash your hands!

With all the hardware in place, you can begin to wash your hands like a pro – and kill off those viruses!