Connected Boot Dryer

[mdszy]

Hey all, just figured I'd share this project I'm currently working on. I have the project shared on Hackaday.io as well if you'd like to see.

It's basically an Internet Connected Boot Dryer. This MaxxDry boot dryer I bought from Goodwill for like $6 has a timer switch on the front and a switch to enable/disable the heater when the timer is active.

I dislike that the timer switch only allows me to run it for 3 hrs at a time. I'd like to not have to manually turn the timer and start it. It'd be nice if I could have it start before I wake up so when I leave in the morning I have nice warm shoes/boots. If you've never used one of these, they're absolutely incredible especially here in Wisconsin where the winters get absolutely frigid.

So I decided to take the thing to pieces and use an ESP32 to make it Internet-connected.

Currently, I've completed creating the ESP32 software and creating the online dashboard to control it, which looks like this. The backend is created using Node Red, and you can see a detailed writeup on hackaday.io about how I did that.



I can enter a start/stop time to schedule it, or manually control the fan/heater. Right now all this does is light up some LED's on my breadboard. I'm currently in the process of getting PCB's made, the first batch didn't work (couldn't program them, and the relay footprints were wrong... thanks to DigiKey providing incorrect footprints) so I'm getting more made.

I'm going to be putting this all in an enclosure and attaching the enclosure to the dryer itself. There is a surprising lack of room inside the thing and the entire enclosure is filled with quite hot air all the time, so I don't really want to be putting the electronics inside anyway.

Here's what the thing looks like all disassembled:



Just figured I'd share this if anyone finds it interesting! I'll be providing all the PCB design/gerbers, schematics, code, etc. once it's all working and I know I've removed all my passwords from the code

[t1d]

I built a reflow oven by controlling a Crydom solid-state relay (switch) directly off of a PIC18F4550 running on 5 volts. The SSR required 7mA to drive it, IIRC, and the IC could supply 20mA off of a pin. My brother wrote the PWM/PID code. My point being that the SSR is a really good/easy way to configure a switch. Just swap the out the original push button switch for the SSR. The MCU can drive it however you like, time-wise, and you can use the MCU for communications. And, you are correct, warm and dry (ski) boots are wonderful.

[mdszy]

I built a reflow oven by controlling a Crydom solid-state relay (switch) directly off of a PIC18F4550 running on 5 volts. The SSR required 7mA to drive it, IIRC, and the IC could supply 20mA off of a pin. My brother wrote the PWM/PID code. My point being that the SSR is a really good/easy way to configure a switch. Just swap the out the original push button switch for the SSR. The MCU can drive it however you like, time-wise, and you can use the MCU for communications. And, you are correct, warm and dry (ski) boots are wonderful.

I see! I'm just using regular electromechanical relays, but I'll look into SSR's for future projects

[mdszy]

So, I think I can call this project "finished"! Here's the hackaday.io writeup.

There are a couple of problems right now.

• Most notably, the board is very bodged. Turns out I swapped the coil/contact on the relays so I had to cut the traces and re-wire them by hand. Oops.
• Turns out the dryer seems to smoke slightly and get GLOWING hot if the heater is on without air being forced over it. I need to take steps to ensure that on a condition where the MCU fails, the heater is guaranteed to be off.
• Speaking of which, the 3.3V rail occasionally drops out. I'm really not sure why. Sometimes the MCU's brownout detector trips and it resets and we're good, other times it never recovers. This leaves the relays in an undefined state, usually they end up turning on.
• I also didn't make much high voltage isolation in the PCB design, nor did I include any fuses. So yeah, I would consider this to be somewhat unsafe as it stands.

But other than that, it definitely works! I'll be testing it more later (with a fire extinguisher by my side, just in case...) to verify that it's totally functional!

[mdszy]

And by "definitely works" I mean "barely holds itself together because I'm a dingus".

Try not to laugh too hard at me for this.

AC isolation is important.

This is present on all the IO all over the board all the time. Guess that could be messing with things.

[NiHaoMike]

Why not just bypass the timer and plug it into a reprogrammed smart plug?

[mdszy]

Why not just bypass the timer and plug it into a reprogrammed smart plug?

Where's the fun in that?

[mdszy]

Aaaaand it's officially complete!

I have the full project details on the Hackaday.io page as mentioned earlier

I redesigned the PCB to have better AC isolation.

As I should have expected, the AC was coupling horribly into the circuit because of the lack of ground plane isolation. But now it works perfectly just as designed!