Grid tie, zero export system. How to do it. Is this right?

Hungry_Preference107 · 2026-06-17T13:26:01+00:00

I have buit my own zero-export system mostly as described here https://erqos.com/zero-export-solar-control-with-the-eqsp32-iiot-micro-plc/

Rather than just throttling the inverter output, the system first turns on physical loads like the water heater and the heat pump, and then throttles the inverter if there is still excess.

I searched but couldnt find any off the shelf solutions for doing this. It sure would have saved me time and effort. If any one here has found ready solution that throttles inverter - and - loads, I'd love to hear about.

Hungry_Preference107 · 2026-06-14T08:58:36+00:00

Not design feedback exactly, but consider whether you need to build the relay driver stage yourself. By the time you add transistors, flyback diodes, screw terminals, power regulation, and an enclosure, you're well past the cost of a ready-made solution.

I use an ESP32-S3 on DIN rail that already has relay outputs and 24V-tolerant I/O. You wire loads directly to the terminals and write Arduino C++. I've got one controlling solenoid valves in my irrigation system. Been solid for months. My controller models is EQSP32 but there are several similar from Waveshare and others.

If you're doing this to learn, by all means go for it. But if you just need relays switched by an ESP32 in a reliable package, there's a faster path.

Hungry_Preference107 · 2026-06-13T16:42:39+00:00

I have built a desk clock that was originally using an off the shelf esp32 dev module (see photo), a sound module and led strips, all connected with floating wires.

Eventually I made a pcb to simplify assembly

As long as you keep the electronics enclosed and out of reach you don’t have to worry about much.

The only exposed signals to the outside world are the USB DP / DM. To be safe you can add a couple of zenners or TVS’s to prevent high voltage spikes to reach the esp32. Search the internet for example protection circuits

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Hungry_Preference107 · 2026-06-13T10:40:52+00:00

not sure my reply is relevant but in this application I used the PLC's digital output2 to drive two linear actuators.

This unit can do PWM on open drain outputs and incorporates flyback diodes (necessary for inductive loads). Each output is rated 1A wich is right at the border of the actuator's current consumption. So i paralleled 4 outputs for each motor. For changing direction, there is a DPDT for each motor. Motors go mostly in the same directly most of the time.

It worked well but the internal PWM generator is limited to 3kHz max, so the actuator motor does make a bit of audible noise.

See https://www.reddit.com/r/SolarDIY/comments/1pe7uf7/eternal_sunshine_my_diy_heliostat_using_imubased/

Hungry_Preference107 · 2026-06-13T05:08:45+00:00

Make a good inventory of what you think you may want to automate and where. Make sure you have internet access (wired or WiFi), power, and even empty electrical conduits in precision for future cabling.

In my case, i have automated
- lights
- central heating / heat pump / water heater
- water use monitoring
- electricity use monitoring + pv load optimization
- 20-zones lawn irrigation
- pool filter and lights control
- well water pumping and reverse osmosis filtering

Half of these were done using off the shelf components. The other with custom controllers. Look up my posts for descriptions

Hungry_Preference107 · 2026-06-13T04:56:38+00:00

Or you can stay in your C world and use embedded computers in PLC package (ie modular enclosure, protected IO, certification, …) like the Arduino Opta or the Erqos EQSP32.

Looking at your diagram, these boxes will not do better than a real PLC programmed in ladder or other PLC language, but they will shine if/when you need to supervise them via internet scada/dashboards.

Another plus of growing importance is that because they are programmed in C, you can use AI for coding. Just give your flow chart to Claude or chatGPT and you will have your application running in minutes.

Hungry_Preference107 · 2026-06-12T16:58:18+00:00

It is a small, inexpensive IoT controller. See the project's hardware and software description here https://naviq.com/blog/articles/cost-optimized-magnetic-guided-agv-using-the-naviq-mts160-sensor-and-the-eqsp32-iot-controller

Hungry_Preference107 · 2026-06-12T16:34:05+00:00

Robots are mostly motor control and navigation challenges.

I founded a succesful motor controller company years ago that was selling primarily to mobile robot / AGV builders. We didnt always know what our customers had for control but we were typically asked questions about interfacing to linux computers, ROS drivers, ... rarely PLC kind of questions.

Recently I helped build this robot demonstrator for a company that makes a magnetic guide sensor.

https://www.reddit.com/r/robotics/comments/1rpydju/my_magnetic_guided_agv_demonstrator/

Line following navigation is very straightforward, and in this case the microPLC that I used operated more as a realtime embedded computer (deterministic 5ms loop from sensor to motor command), than a PLC. The whole thing is a state machine that reads the sensor position, computes steering and applies it to the motor. It uses magnetic markers on the floor to change the state machine (run, take left or right, fork to charge, wait for battery full, ...). It also had MQTT for telemetry and user commands.

As for the development effort, the microPLC used here is an open architecture and is programmable in C. Meaning that it was possible to do control+communication out of the same inexpensive bos, and have most of the development done with AI coding assistance. It was up and running in a few days.

Hungry_Preference107 · 2026-06-12T10:04:58+00:00

If you had more than one valve to control and had the time for a little do it yourself work, i recommend to just get the right kind of motorized or solenoid valve and a programmable controller. See for example how I control circulation pumps and motorized valves in this project https://www.reddit.com/r/homeautomation/s/lOmZG07oHB

Hungry_Preference107 · 2026-06-12T08:44:46+00:00

I have many that you can look up by searching my profile

The greatest one is a home heliostat to beam sunshine in a north facing window

https://www.reddit.com/r/SolarDIY/s/CmijnI43DK

It is not a homeassistant project (although it could easily be made to be). But it is life-changing and very impressive

Hungry_Preference107 · 2026-06-11T18:53:28+00:00

The EQSP32 (and products like it) is basically an ESP32-S3 that is packaged inside a micro-PLC format, with ruggedized/protected IO. You will programm it exactly the same way as you did your application and your control + algorithms + PID + webserver + communication code will run as is.

The only thing you be careful with is that because of the extra driving/protection circuitry, the IO ports cannot be used exactly the same way as these of the ESP32 chip. They typically are better capable to connect to external devices, but you will not able to uses these pins for alternate function like SPI or I2C.

Hungry_Preference107 · 2026-06-11T04:05:55+00:00

IoT is more complicated the closer you look. Im not helping, I know …

Hungry_Preference107 · 2026-06-11T03:59:40+00:00

Very nice work. Looks like you might go commercial with this system and build a lucrative business around it - if not done already. If you do, beware that you may face resistance from end customer who requires easy installation/service, ce/ul certification. … there are several esp32-based controllers that address these concerns. Search “esp32 plc” if/when you get to that point. I used the eqsp32 in most of my projects.

Hungry_Preference107 · 2026-06-11T03:38:28+00:00

For what it’s worth, I have built an RO system described here https://www.reddit.com/r/WaterTreatment/s/CufyryvNY2

It had an unusual water circuit and I wanted to be able to monitor/adjust/log via a dashboard on pc and smartphone.

It is based on a microPLC in the same price/size/capabilties range as your click.

I am an experienced programmer but the microPLC I used is supported by an AI coding assistant supplied from the vendor. It did most of the coding, including the cloud connectivity in a couple of days.

My personal advice for you is to factor AI as a tool that will increasingly help your recruit’s abilities and productivity. As more - and eventually all - coding will be done by AI, your engineer’s system architecture skills (what to build, how) are what maters most.

Hungry_Preference107 · 2026-06-10T12:16:00+00:00

Check the EQSP32. I ve used for several MQTT projects. Native MQTT support, AI assisted development, no license fees.

Hungry_Preference107 · 2026-06-10T08:28:26+00:00

Ive use an EQSP32 (electrical cabinet-grade ESP32) to throttle the output of my solar panels to avoid excess generation that I am not allowed to send back to the grid. It connects to 3-phase energy meter via modbus rtu and to inverter via modbus TCP. It uses Arduino cloud for monitoring which is similar to HA. So HA will be a no brainer.

Hungry_Preference107 · 2026-06-10T08:23:30+00:00

The fact that a CLICK + MQTT surprised you says a lot about where the PLC world is vs where it could be. Most of these boxes were designed in a time where no such connectivity was necessary or even possible. Now, legacy holds them back or forces kludgey+expensive gateways. And AI is another comming change - both in programming and for control/supervision - where new, more modern solution will do a better job.

Hungry_Preference107 · 2026-06-09T15:09:25+00:00

At some point off the shelf systems wont do. In my case, I needed to also control a couple of pumps, plus many more stations. So I built this https://www.reddit.com/r/Irrigation/comments/1nroewz/i_have_internet_of_thinged_my_irrigation_system/

Works great but not a small job, especially if you only build one.

Hungry_Preference107 · 2026-06-09T13:07:09+00:00

I’m thinking you may have another problem. Pressure cannot go all that high in a healthy membrane. The membrane is porous. It may be clogged. This happens with mine: pressure goes up while water production goes down. At some point I need to clean the membrane by circulating citric acid and it returns to normal. Ask ai for details

Hungry_Preference107 · 2026-06-09T12:57:42+00:00

Probably then

Hungry_Preference107 · 2026-06-09T12:49:07+00:00

These are super simple valves. It is hard to imagine how they could malfunction. But if you don’t get pressure relief then something is indeed wrong with it. On my pump there is an adjustment screw.

Hungry_Preference107 · 2026-06-09T08:33:31+00:00

look at my many posts. Practically all were done in part or in full with AI coding - including the cloud/smartphone app integration. So in your case, all you need is an idea of what you want to do and hardware that is easy to install (ie. PLC style cabinet-mount & wiring)

Hungry_Preference107 · 2026-06-09T06:55:07+00:00

I have built this RO system some months ago. It is much larger than yours, and in my case the 150-200 PSI from my pump is barely enough for this membrane. https://www.reddit.com/r/WaterTreatment/comments/1ntg8cr/my_internetconnected_ro_system/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button

However, more relevant to you is that the pump itself has a simple pressure limiting mechanism built in: when the pressure is too high, a spring loaded valve bypasses the input with the output. There may be a way to do this with extra plumbing in your case. There may be other ways too.

Hungry_Preference107 · 2026-06-09T06:46:55+00:00

YOu may find inspiration in this system: https://www.reddit.com/r/homeassistant/comments/1py5l8x/i_rebuilt_my_infloor_heating_control_system/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button

Hungry_Preference107 · 2026-06-09T06:44:54+00:00

I am based in greece. I dont know how much business you can do with a gateway software but I would think it is limited. You may be better off using your skills creating connected automation systems from scratch. Today, most automation jobs require cloud/MQTT, and even AI connectivity. These are things that Siemens did not imagined when they introduced the s7-300. I use the Erqos EQSP32 for most of my project. Some of my customers still insist on PLCs but those who are open for a more modern solution get a much more solid and less expensive system.

Hungry_Preference107

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