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Sanitizing Wipe Servo Extension
06/06/2020 at 17:27 • 0 commentsI 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!
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Non-standard LED driver
06/06/2020 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.