The global COVID-19 pandemic has inspired engineers to develop many novel health-centric devices. The newest contributor to the outpour of personal health innovations is, surprisingly, NASA.
This month, a team of engineers at NASA’s Jet Propulsion Laboratory released their PULSE pendant, a necklace that will warn you if your hand is about to touch your face.
NASA’s PULSE pendant. Image used courtesy of Lisa Harbottle
PULSE features an elegant design, requiring only a handful of electronic components. These components are 3D printable and can be easily assembled. The design is also completely open-source.
Components You’ll Need to Build PULSE
On their open-source GitHub page, NASA JPL provides a complete breakdown of everything necessary to create a PULSE pendant. This includes schematics, parts lists, STL files for 3D printing the case, and assembly instructions.
From an electronics perspective, the parts list is as follows:
- IR sensor unit (recommended: Pololu 38 kHz IR proximity sensor)
- PNP transistor (recommended: 2N3906 or equivalent)
- 1 K Ohm standard resistor
- Slide switch to fit case
- Vibrating motor to fit case
- W1–5 cm; W2–4 cm; W3–2 cm; W4–2 cm; 22 gage wire
- Heat shrink tubing to cover leads
- Battery holder
- 3V coin battery (recommended: CR2032 3V lithium battery)
All the electronic parts needed to create PULSE. Image used courtesy of NASA JPL
This is an exceptionally simple design, consisting of only nine components (two of which are wire and heat shrink).
The design also recommends dark-colored paint—acrylic, oil, or even nail polish—that you’ll only need if you’re using non-black colored case material.
Most of these parts are very commonplace and can be easily found online.
How PULSE Works
Pulse works by leveraging an IR sensor module to detect when objects (namely your hand) get close to your face. The module they recommend is the Pololu 38 kHz IR proximity sensor. This proximity sensor consists of one TSSP77038 IR receiver and one IR LED driven by a 555 timer-based circuit.
The IR LED, which is directed toward your face, sends out infrared waves. If your hands are near your face, these waves are reflected and those reflections will then be detected by the IR receiver.
Circuit diagram of PULSE. Image used courtesy of NASA JPL
When a reflection is sensed, the proximity sensor sends out a pulse from its OUT pin. This pulse then drives a transistor, which in turn drives the vibrating motor, successfully warning the user that their hands are close to their face.
Not a Comprehensive Prevention from COVID-19
While a useful device, it in itself is not enough to keep wearers entirely safe from COVID-19. NASA JPL explicitly states on a brochure, “PULSE is not meant to take the place of masks or respirators, but only to be a warning device that your hands are moving past the pendant toward your face.”
It is important to understand this and still follow general health guidelines that have been laid out by official bodies such as the CDC and WHO. While the PULSE pendant is not a cure-all solution, when used in conjunction with other health measures, it may help keep you safe.
The PULSE Pendant’s Design Accessibility
The beauty of PULSE is its simplistic design coupled with its accessibility. Its casing is 3D printable with STL files readily available. The circuit is straightforward and easy to assemble with components so commonplace that virtually anybody can get their hands on them. The only cost to the individual is the cost of the parts itself.