A couple years ago I decided to force myself to learn how to program Arduinos and similar microprocessors, the only problem was I didn’t have a pressing need for one, but I knew it would at some point. Naturally, I wondered what kind of cool thing I could make that I hadn’t seen anybody make before.
I figured a wrist mounted flamethrower was the way to go. Now, this project never saw its way to completion, but it got me started with programming a relay to control a 12V powered arc generator. I designed and 3d printed something similar to the caulking gun I used before with this kind of butane canister, just much smaller and lighter.
The main problem with practically deploying this (for me, at the time) was figuring out how to use a motor to apply enough force to compress the cylinder so it would shoot gas into the air. This was a surprising amount of force that it needed, and solenoids (the kind electric locks use) couldn’t overcome static inertia. I considered servos and stepper motors, but that was adding a fair amount of complexity that I couldn’t just whip up yet.
I did a little experiment with my handy power supply, a high-voltage igniter, and a solenoid valve… It’s apparent how happy I I am with the results in this short.
Once I saw that 12V would drive this thing, I needed a way to control the load to the arc generator and the solenoid valve with an ESP 32 (top right). I had some of these commonly available relays kicking around (left), but they can be finicky with 3.3 V, so I used a logic level shifter (center). On the top left is a adjustable buck converter that drops 12 V down to 5V to power the ESP 32 and the relays. The ESP has its own voltage regulator and tends to do quite well on 5V. I’m pretty sure I could have used a 7805 voltage regulator instead of a buck converter to do this, but I haven’t tried that yet.
Everything was going according to plan. I used the ESP Now library https://randomnerdtutorials.com/esp-now-esp32-arduino-ide/ to have one master chip control multiple helper chips (yeah, I’m calling it a master-helper relationship from here out). This way, I could test the flame proofer remotely over a locally created wireless network independent of my LAN. I wired together a hacky mechanically debounced pushbutton board to signal the master, which in turn signaled the helper.
Now, given that my proto-boarding abilities are mediocre at best, and given that I had to make five more of these (this will be explained later), and given that a PCB would only have the components I needed on it (no unnecessary screw terminals, jumpers, etc.), I decided it would be a good idea to just design a PCB, have a bunch printed in China, and have them delivered to my house within a week. I do most of these experiments between the hours of 10 PM and 2 AM, obviously not every night because I would die. The five day wait was tolerable.