It's sad that we have to wear face masks due to Covid -19. It's not a very enjoyable experience, makes you hot, sweat, nervous and of course harder to breath. There are thirsty times when you are urging to remove the mask but scared to do so.
What if the face mask could open up when in a safe environment, with no people around. So you can cool down and drink. But to make it safe again, the mask should be able to shut off when anyone is approaching.
Since this is a wearable project, I started mocking up a cardboard prototype, this is the fastest and cheapest solution for the correct dimensions, etc.
The plan is to use an Arduino Nano that read signals from 3 PIR sensors, if any sensor triggers positive, then it shuts down the door by controlling the servo, and lights up LEDs to tell which sensor is triggered.
Some parts I used:
3D printer I used this one: https://amzn.to/3cfC9X1
PIR Sensor: HC SR 501 https://amzn.to/3cfC9X1 (Amazon)
Mini Servo: https://amzn.to/3cfC9X1 (Amazon)
Wire sleeve: https://amzn.to/3cfC9X1 (Amazon)
Water decal paper for laser printer: https://amzn.to/3cfC9X1 (Amazon)
Protoboard https://amzn.to/3cfC9X1 (Amazon)
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Under the lens of the HC-SR501 sensor, there are actually 2 sensors and a comparator circuitry. It sends out HIGH when the 2 sensor readings are different.
So if the sensor is stationary, the background will make 2 sensors with same reading, when a person or object with heat radiation walks by, one of the sensor will read the difference, thus trigger the module.
However, if you install the sensor on a moving platform, the constant motion will trigger the module often because environment, even though there is nobody come across. Pretty much everything have IR radiation.
Though it's not the exact sensor to detect human, it works for the mask application, even makes it safer since it always false positive to keep it shut.
To cover the full 360 degrees around you, I picked 3 sensors, 2 on the cheek, and one on the back of head. The sensor has a 110 degree range so that adds up to almost a full circle.
2 white ball(lens) on cheek will be quite funny looking like a clown, so I started some rough sketches, for a sci-fi look. With that style in mind and earlier dimensions from the mock up, we can start 3d modeling
I used fusion 360, starting form the major parts and mechanisms, then adding more details for the sci-fi look.
The connection is quite simple, a lot of 5V, GND and digital pin connections. Since the Arduino Nano has very limited power ports, I created my own expansion using protoboard and some pins. Just solder all the wires together to make a rail.
I also made a lot of connectors(turned out not necessary and caused a lot of trouble), at a time I made a 4 pin connector that I have to figure out direction every time. Later I updated them using the Poka-Yoki philosophy, which is make all the parts coming together in an only possible way.
Very straight forward coding, basically a condition loop. When any sensor is triggered, it shuts down the door immediately and lights up corresponding LEDs.
See code attached:
Check how it works in the video.
There are 2 disadvantages of this design.
1. The sensor false positive problem, a better sensor or even camera with AI would make it more accurate.
2. I didn't put in effort to seal the mask properly, but had thought of how to seal the door area. I think the fish mouth could be a very interesting mechanism to test out in the future.
This is not by any means a perfect project, but hope this could be your inspiration or entertainment.
Thanks for watching and see you next time!
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