Many years ago I saw for the first time a video on YouTube of an useless machine and I was fascinated by the simplicity of the concept.
So I decided that I wanted to build one myself.
The first issue I had to face was the box itself. I was uable to find a box that suit the style I had in mind (at that time I didn’t own a 3d printer yet). So the project was abandoned.
When In 2014 I bought my first 3d printer I resumed the project and started to build the first attempt.
Sadly the sg90 I had were not strong enought to push the switch, but I didn’t want to spend to much money on components so I tried some mg90s I bought on a chinese site. This time those were almost able to push the switch (I choosed a really stiff switch).
So I decided to add a small gearbox to the design and eventually the servo was finally able to push the switch 100% of the time.
Meanwhile, due to lack of time and too many things I wanted to do, this project went on hold till the infamous 2020 lockdown when I restarted it and finally completed.
The main brain of the machine is a Microchip PIC12F1572 that has only 3.5kb of program memory but 3 hardware PWM that are perfect to control the servos, and it can run at 5v so no need to generate different voltages.
The other components are two servos a sg90 for the top gate, and a mg90s for the hand, a buzzer that beeps when the switch is pressed by the user, of course the switch, and a led to spice up the interaction.
Everything is keep together by a perfboard, 36 m3 screws (too many) and powered thru a micro usb connector.