This repository contains the open hardware design files for the Twomes OpenTherm Monitor device, consisting of:
- a Twomes OpenTherm Monitor Shield with a WeMos D1 Mini shield form factor, to be placed on;
- a WeMos D1 Mini board, such as the LilyGO TTGO T7 Mini32 V1.3 ESP32.
The OpenTherm Monitor Shield is connected via one pluggable terminal block with screws to connect one wire pair leading to a boiler that supports OpenTherm and via another one pluggable terminal block with screws to connect another wire pair leading to a thermostat that supports OpenTherm. The Twomes OpenTherm Monitor can upload this measurement data to a Twomes server via Wi-Fi using secure HTTPS.
N.B. This is device is NOT an OpenTherm gateway; it only monitors OpenTherm traffic and it cannot insert OpenTherm commands to the boiler or thermostat.
This repository contains the open hardware designs files for the Twomes OpenTherm Monitor device, It also includes a docs folder with recent printouts of the schematics and PCB layout.
The associated firmware that you can run on this device can be found in this repository.
To fabricate the printed circuit board you can use various PCB services.
The folder pcb/jlcpcb includes all exported files needed to have the PCBs manufactured by JLCPCB. Upload the zipped gerber files to the JLCPCB quote page, select the amount of PCBs and a colour for the silkscreen. All other options can be left on default. If SMT assembly is desired, also select this option before ordering. This will take you to a page where the BOM and POS file can be uploaded. Use the files BOM-TwomesGateway.csv and CPL-TwomesGateway.csv.
N.B. The pluggable terminal blocks we used (see features are not listed the BOM-*.csv file; they need to be ordered separately other services and soldered manually.
To fabricate the enclosure you can use your own 3D printer or use a 3D printing service.
The folder enclosure/fabrication contains exported STL files for the case and lid of the Twomes OpenTherm Monitor. The STL files can be imported into any slicer and turned into G-Code for a 3D printer.
To change the hardware design of the PCB, you need:
- KiCad installed to change te PCB design.
The KiCad source files of the PCB can be found in the folder pcb.
To convert the PCBs into a format suitable for fabrication, consult the webpage of your PCB manufacturer of choice. For example, see the JLCPCB guide on how to export Gerbers and the JLCPCB guide how to export the BOM and POS files. You may also use a KiCad plug-in for this purpose such as kicad-jlcpcb-tools.
To change the hardware design of the enclosure, you need either:
- Autodesk Fusion 360 installed (Autodesk provides 30 day free trials and free one-year educational access to its products and services for eligible students, teachers and research staff);
- or FreeCAD, an open source alternative.
The source files of the enclosure can be found in the folder enclosure. We include both .f3d source files and .step source files we obtained after conversion.
The Twomes OpenTherm Monitor Shield is a WeMos D1 Mini shield that features the following main hardware components:
- two terminal blocks CTB9209/2, pluggable into terminal block headers CTB9359/2 (one for thermostat, one for boiler), each with two positions;
- two optocouplers that electrically separate the OpenTherm circuit on the shield from the monitoring logic on the shield and the main board: the OpenTherm communication between thermostat and boiler still works even if the main board receives no power via its micro USB port or has crashed;
- recessed button that is positioned behind a pinhole in the device enclosure, which allows the end-user to do a Wi-Fi reset.
To-do:
- change design and JLCPCB files to take advantage of the new one-sided hand-soldering option for through-hole parts for the pluggable terminal blocks
J1andJ2and the pin headersP1andP2;
Project is: in progress
The hardware designs in this repository are available under the CERN-OHL-P v2 license, Copyright 2022 Research group Energy Transition, Windesheim University of Applied Sciences
This open hardware design is a collaborative effort of:
- Marco Winkelman · @MarcoW71
- Sjors Smit · @Shorts1999
Thanks also go to:
- Henri ter Hofte · @henriterhofte · Twitter @HeNRGi
We use and gratefully acknowlegde the efforts of the makers of the following designs:
- KiCad Libraries, by the KiCad Development Team, licensed under an adapted version of the CC-BY-SA 4.0 License
- Opentherm-monitor. In Elektuur, 7-8/2001, pp. 22-23.