Listed is the problem happened in chronological order.
1. 5VDC power supply module
You know that cheap-ass PSU module that’s scrapped from other things and sold on marketplaces, yeah. Got it, tested it, it works, screw it in, plug it in, then it stopped working.
Solution: noticed that I have a pretty small 5V 3.6A power brick, it still fit in the box, so I’m going to use that instead.
2. DuPont connectors aren’t stable enough
You can see it on the design post, I plan just mounting the ESP32 upside down, crimping female DuPont. It’s too unstable. The screen is flickering. Encoder will not detect turns most of the time.
Solution: crimp JST plugs on the parts, and solder everything on perf-board.
Downside: I did not plan my positioning tight enough, so it’s too far apart, too large, and awkwardly mounted on the designed mounted parts. Messy but everything still fits inside.
3. Fotek SSR cannot be driven by 3.3V
Despite what it says on the label (IIRC, 3-25 VDC). Despite the LED lit up. It cannot open the gate at 3.3V. I’ve mentioned how terrible Fotek SSR was multiple times. But it its dirt cheap, and I already have some around. I’m not going to get a better SSR for this. There are two ways to go about this.
First, the easy but may kill the ESP way. Splice the 5V to + on Fotek, and - to a pin. So setting the pin to LOW will trigger the SSR and turn on the heater. A quick google will tell you that some pins on the ESP can handle up to 6V. But on spec, all pins are limited to 3.3V. This worries me, I believe by doing this, if (or when) the ESP fail, the SSR will remain triggered and it’ll become a fire hazard. So I went with the second solution, the “right” way.
Which is adding a MOSFET as a relay to control the 5V. So I have the ESP to control the 5V for the SSR that control the AC line. it’s like relay on top of relay.
4. Water heater isn’t grounded
Once everything is fixed and device is up and running, I did a test run, and want to confirm the water furthest away still has the same temperature, I felt electric current when pulling out the type-K probe. Curious, grabbed my test pen to confirm, lit up like a Christmas tree. With the amount of projects using these out there. I honestly cannot believe people hasn’t noticed this problem yet. After confirming that, a quick google led me to this water heater on Amazon, “no electric shock during use” was literally in one of the pics. JFC!
Solution: grab a piece of wire, attach it to a metal thing and ground. Problem solved.
5. The water heater goes POP!!
It exploded! (the hero image) After #4 is fixed, I went on testing another thing, only the coily part that is submerged in water. Because I plan on using a wide but low container, I don’t want to use too much water. After 15 minutes or so, the LED goes pop, plastics melted. Everything else still works okay, though I noticed the ESP kept on restarting. Seems like the water heater has shorted something. To the bin it goes.
Solution: back to the drawing board. Hopefully I have something to update...