Guides on E&G Code

Connecting an RS485 converter to an ESP32

Sat, 17 Oct 2026 00:00:00 +0000

Many home systems use RS485: radiant floor heating, photovoltaic inverters, heat meters, heat pumps. An ESP32 has three serial ports, but it operates at 3.3 V with signals referenced to ground; the bus, however, uses a differential pair of wires. In between, a converter costing only a few euros is required. This guide explains how we connected it in two real-world cases, on a relay board and on a wall touch panel, to make them communicate with the bus of a Radiax radiant floor system. The mistakes we made are the most common ones, and you will find them here in advance.

A temperature and presence node with ESP32-C3, SHT30 and LD2410C radar

Sat, 17 Oct 2026 00:00:00 +0000

A commercial WiFi thermostat costs about thirty euros, often depends on an app and a cloud, and suffers from humidity in the bathroom. With an ESP32-C3 SuperMini, an SHT30 probe on a cable and, if you want, an LD2410C radar, you can build a node that measures temperature and humidity, knows if someone is in the room, and communicates with Home Assistant via MQTT or the ESPHome API. These are the sensor nodes of ORFHAn, but they also work standalone, with any home automation system.

A Tuya thermo-hygrometer without cloud, with OpenBeken

Sat, 17 Oct 2026 00:00:00 +0000

WiFi thermo-hygrometers costing only a few euros have a readable screen, a good probe, and one flaw: to function, they pass through the manufacturer’s cloud and an app. If the internet goes down, or if the service closes one day, the measurement stays on the display and no longer reaches anyone. Many of these sensors contain a Beken chip, and on that chip runs OpenBeken, a free firmware that speaks MQTT directly with the home network. This guide explains how we did it on an Emylo H&T S09 to use it as a room probe in ORFHAn, but the procedure applies to other similar models.

The circulator pump of a radiant floor: who enables the pump

Sat, 17 Oct 2026 00:00:00 +0000

Anyone replacing a radiant floor controller usually thinks about the zone valves: one relay per room, an actuator that opens, and that’s it. Then they turn everything on, the valves open, and the floor stays cold. The reason is often dozens of meters away: the pump that sends water to your apartment does not start on its own. In many apartment building systems, the circulator pump is located in the stairwell, inside the user “satellite,” and is turned on by a relay board that obeys the home controller. Once that is removed, no one asks it to run anymore.

How a Radiax radiant floor system thinks, seen from the bus

Sat, 17 Oct 2026 00:00:00 +0000

A Radiax radiant floor system, as seen from home, is a wall display, a few probes in the rooms, and a box in the manifold compartment. Seen from its bus, it is something else, and many choices that seem strange, such as the pump staying on or the system not restarting without a display, become logical. This guide summarizes what we understood by listening for weeks to the bus of a system in use with rehumatism. It is intended for those who have such a system and want to understand it, for those who have to repair it, and for those who want to connect something to it, as we did with ORFHAn.

Why a radiant floor does not regulate like a radiator

Sat, 17 Oct 2026 00:00:00 +0000

A radiator heats the air in a few minutes: close the valve and it stops. A radiant floor is a different beast. The water flows through pipes embedded in several centimeters of screed, and the screed acts as an accumulator: after the valve has closed, it continues to heat for an hour, and after it has reopened, it takes an hour to be felt. Regulating it like a radiator works, but poorly. This guide explains why, and how to regulate the ORFHAn valves using a time-based PID controller.

Testing a relay board on the bench, before opening the panel

Sat, 17 Oct 2026 00:00:00 +0000

Replacing a radiant floor controller with a homemade one is an afternoon’s work, if everything goes well. If something goes wrong, it’s a cold house in January with firmware to fix and an open panel. The difference is made by what you test beforehand, on the bench, while the original system continues to function. This is the procedure followed by ORFHAn, but it applies to any relay board with an ESP32 or another microcontroller.