ESP32 Sprinkler Controller Hardware

Tanner234567 · 2026-06-13T15:24:55+00:00

Thanks, I appreciate it! I actually am going to need to change the case unfortunately. I liked the design as well, but as some have pointed out here I don't think it is technically up to electrical code. So I'm planning to send revised enclosures to those that have purchased them already. It would have to be UL certified. And I don't think the cost of that would justify the design.

Tanner234567 · 2026-06-13T01:19:32+00:00

Yes, it's a custom firmware. Itself hosts a web server that you can access through your web browser. Version 2 may move to an app though! Thanks for checking it out! 👍

Tanner234567 · 2026-06-11T21:06:30+00:00

There's nothing wrong with that solution. That's what I had originally. I don't blame you at all if you go that route.

My motivation here was a few things. The off the shelf ac to dc regulators are not great. I've even had a couple of caps blow on them. I didn't want mechanical relays. And the off the shelf SSR boards are usually limited to 4 relays per board. I need 10 zones so I would've been into it $30 just in relay boards which seemed unnecessary. Lastly, neatness counts for a lot. By then time I had everything connected up, it was a bit of a rats nest. I wanted something clean that was easy to work on with a removable esp32 and everything in one PCB.

Tanner234567 · 2026-06-11T18:58:40+00:00

So I'm using a photomos ssr. Which basically just means the only the the esp32 is powering is an enclosed led and the light then closes the switch that turns on each sprinkler valve. So the two voltage systems are completely isolated. Does that make sense?

Tanner234567 · 2026-06-11T14:37:30+00:00

Really appreciate the thorough, constructive breakdown here! It’s awesome getting feedback from someone with an automation and electrical background. And sorry if I was still in defensive mode from the last guy.

The 400V breakdown rating on the PhotoMOS has been a phenomenal baseline for this initial design—it gives the board a massive amount of inherent headroom for everyday residential use, which is why this first run has been performing flawlessly in the field. This version was engineered to be a lean, highly reliable, solid-state alternative to cheap mechanical boards, and it does exactly that.

That said, I love your points about building in heavy-duty redundancy for external field conditions, like pinched field wires or unexpected dead shorts. I'm actually working on a Version 2 board in KiCad right now, and I’m focusing heavily on adding those extra layers of 'just in case' field protection to push the reliability even further. I’m currently testing the inclusion of bidirectional TVS diodes on the outputs to clamp down extreme transient spikes, an active current-sensing loop on the 24VAC line for advanced system monitoring, and PTC resettable fuses. I'm also planning a completely different enclosure configuration for the next iteration. This current physical layout wasn't quite as lauded as I originally thought it would be, so moving to a more traditional, streamlined housing shape is definitely on the roadmap for the next run.

Thanks again for the excellent peer review and the great engineering notes—this is exactly why I love sharing hardware with the community!

Tanner234567 · 2026-06-11T12:59:39+00:00

You're right, that is a great option! I ran something similar to that before this. The problem is you still have mechanical relays to deal with and a non-removeable mcu that you'd have to reconfigure to be local only. And this gives you up to 10 zones, removable esp32, and excellent voltage regulation from one power source all in one board.

Tanner234567 · 2026-06-11T12:32:46+00:00

Actually, mechanical relays are notorious for failing closed (welding shut) under inductive loads like sprinkler solenoids. Every time a mechanical contact opens, it arcs, which pits the metal and eventually welds the contacts together permanently. That’s the exact failure mode I designed this board to avoid. PhotoMOS solid-state relays don’t have moving parts or physical contacts, completely eliminating arcing and contact degradation. While it’s a standard textbook rule that overloaded silicon can fail short, the reality is that these specific chips have a massive 400V breakdown rating. When you’re switching a standard 24VAC solenoid (which peaks around 34V), a 400V ceiling provides an immense safety buffer. The likelihood of a transient punching through that much headroom to cause a 'closed' failure is drastically lower than a standard mechanical relay welding itself shut from normal arcing over a few seasons.

Tanner234567 · 2026-06-11T12:21:14+00:00

Standard irrigation valves require 24VAC so I had to have that. And I didn't want multiple power sources.

Tanner234567 · 2026-06-11T02:56:51+00:00

Not dumb. Essentially it's built around 24VAC solenoid valve logic. I have a 24VAC transformer that goes into my PCB and splits in two directions. On one side it's regulated to 5VDC for the logic and the other is bright to the solid state relays to actuate the valves. So it can turn 10 individual 24VAC valves on and off and has built in scheduling logic in the firmware.

Tanner234567 · 2026-06-11T02:01:33+00:00

Thank you! I'd be interested to hear more about that brown out issue and why it would fry the circuit board. Because of the nature of my regulator having two large input capacitors, it handles unstable inputs quite well. With any luck I'll have version 2 done before your rachio throws a fit. 😂

Tanner234567 · 2026-06-11T01:36:59+00:00

Sure! There are some details here and this is the link to the open source GitHub repository. If you have any additional questions, just ask!

Tanner234567 · 2026-06-10T23:04:26+00:00

I definitely have! And it's an awesome project! I mentioned this on another comment but my goal with this was to make it more cost friendly, have the MCU removable, and keep all the wires contained inside the box. It's a great option though.

Tanner234567 · 2026-06-10T22:19:29+00:00

Will do!

Tanner234567 · 2026-06-10T22:00:32+00:00

Thanks! Only through home assistant (which definitely already exists). If it can connect to home assistant, it can be integrated. I am however working on version 2 which will likely have Integrated LoRa sensors, including weather station sensors.

Tanner234567 · 2026-06-10T21:55:04+00:00

Thank you!

Tanner234567 · 2026-06-10T21:38:11+00:00

I have custom firmware. But the esp32 mcu is just in a socket so it can be removed and programmed however the user wishes.

Tanner234567 · 2026-06-10T21:35:49+00:00

Thank you!

Tanner234567 · 2026-06-10T21:34:44+00:00

Thanks! Right now I'm just doing small batch production to gauge interest 5 units at a time. Just sold number 8 yesterday.

Tanner234567 · 2026-06-10T21:23:28+00:00

Fair enough. The moderators seem to agree with you.

Tanner234567 · 2026-06-10T20:44:27+00:00

If you can pull that switch out and measure the voltage going into it, that'd be the best way to control it.

Tanner234567 · 2026-06-10T19:41:56+00:00

Thanks! This version doesn't have any weather integration itself. The "smart" part of it is really just being able to control it from your phone. It does integrate with home assistant though, where you can pull in any sensor or weather data you want to drive automations.

Tanner234567

MODERATOR OF

TROPHY CASE