OVERVIEW
OPEN_TEMP is an open-hardware measurement board developed as part of OPEN THRUST LAB, a community-driven project building open-source test benches for drone motor characterization.
The board reads NTC thermistors to log temperatures on the test bench (for example motor, ESC and battery). Each NTC sits in a voltage divider with a bridge resistor; the divider voltages go through an RC input filter to an Analog Devices AD7124-8: a 24-bit sigma-delta ADC with 8 differential or 15 pseudo-differential inputs, a programmable gain amplifier, an internal reference, programmable excitation currents and an SPI interface to the host.
It follows the same tooling as its sister boards OPEN_PHASE and OPEN_WEIGHT: KiCad 10, KDT hierarchical template, KiBot outputs generated by GitHub Actions, self-contained libraries.
STATUS
This revision is at the very beginning. What is in the repository today:
| Area | State |
|---|
| Schematic | Sheet structure and documentation pages in place, functional sheets not drawn yet |
| Mounting holes | 4 × M3 (H1–H4) to GND, drawn |
| PCB | Empty board: KDT drawing pages, JLCPCB 4-layer stackup and design rules, no outline yet |
| Libraries | lib/ created (mounting hole); AD7124-8 symbol, footprint and 3D model to add |
| CI | KiBot runs the DRAFT variant (schematic PDF, netlist, BoM, this README) |
See DESIGN DECISIONS for what has to be decided before drawing the schematic.
SPECIFICATIONS
Electrical specifications (target)
| Parameter | Value |
|---|
| Sensors | NTC thermistors |
| Number of channels | To be defined (AD7124-8: up to 8 differential or 15 pseudo-differential inputs) |
| ADC | AD7124-8, 24-bit sigma-delta, PGA, internal reference, SPI |
| Measurement | To be defined (ratiometric divider recommended, see DESIGN DECISIONS) |
| Temperature range and accuracy | To be defined |
| Supply | To be defined (AD7124-8 AVDD: 2.7 V to 3.6 V) |
| Host interface | SPI (SCLK, DIN, DOUT/RDY, CS), connector to be defined |
Physical specifications
| Parameter | Value |
|---|
| Project name | OPEN_TEMP |
| Board name | AD7124-8 |
| Parent project | OPEN THRUST LAB |
| CAD tool | KiCad 10 |
| Automation tooling | KiBot + GitHub Actions |
| Hardware licence | CERN-OHL-P v2 |
| Dimensions | To be defined |
| Stackup | 4 layers, JLCPCB JLC04161H-7628, 1 oz outer copper, ENIG |
| Mounting holes | 4 × M3, connected to GND |
SCHEMATIC ARCHITECTURE
Five functional hierarchical sheets (under Project Architecture), plus the documentation sheets (Block Diagram, Power - Sequencing, Revision History):
| Sheet (file) | Description |
|---|
AD7124-8_ADC (AD7124-8 - ADC.kicad_sch) | IC1 AD7124-8 (LFCSP-32, 5 × 5 mm): supplies, decoupling, reference, clock, SPI to the host connector. To draw. |
NTC_Inputs (NTC - Thermistors.kicad_sch) | One channel per NTC: bridge resistor + NTC divider, RC input filter, to the AIN inputs of the AD7124-8. To draw. |
Power_Supply (Power Supply - Analog Rails.kicad_sch) | AVDD analog rail and IOVDD digital rail of the AD7124-8, from the host supply. To draw. |
Connectors (Connectors.kicad_sch) | NTC probe connectors and host connector (SPI, supply, GND). To draw. |
Holes, Fiducials (Holes - Fiducials.kicad_sch) | Four M3 mounting holes H1–H4 connected to GND. |
DESIGN DECISIONS
To decide before drawing the schematic, then to record in the sheet notes and in this README:
| # | Decision | Notes |
|---|
| 1 | Number of NTC channels | Sets the AIN allocation and the connector count. |
| 2 | NTC part (resistance at 25 °C, B coefficient) and temperature range | Sets the bridge resistor value and the resolution in °C. |
| 3 | Bridge resistor: value, tolerance, temperature coefficient | Dominates the accuracy once the ADC is calibrated. |
| 4 | Reference: ratiometric or internal | Ratiometric: the dividers are supplied by the voltage used as ADC reference, so supply drift cancels out. |
| 5 | RC input filter and protection | Corner frequency against the chosen output data rate; ESD if the probes are on long cables. |
| 6 | Power: host supply voltage, AVDD regulator, IOVDD level | AVDD 2.7 V to 3.6 V. |
| 7 | Host connector and pinout | SPI, optional SYNC, supply, GND. |
| 8 | Board size and mounting | Fits the OPEN THRUST LAB test bench. |
HOW TO USE
Prerequisites
- KiCad 10 (files are saved in KiCad 10 format and cannot be opened with KiCad 9 or earlier)
- Nothing else: every symbol, footprint and 3D model goes in
lib/ and is referenced relative to the project (KIPRJMOD, project-local sym-lib-table / fp-lib-table)
- KiBot for automated output generation, Docker recommended for local CI runs
Generate outputs locally
./kibot_launch.sh # default configuration
./kibot_launch.sh -v CHECKED # specific variant
| Variant | Outputs | ERC/DRC | Typical use |
|---|
DRAFT | Schematic only | — | Early design work (current CI setting) |
PRELIMINARY | Schematic + PCB | — | Layout iterations |
CHECKED | Full | ✓ enforced | Design review |
RELEASED | Full | ✓ enforced | Tagged version releases |
REPOSITORY CONTENT
| Content | Description |
|---|
| Schematic sources | KiCad hierarchical schematic, 10 sheets |
| PCB layout | KiCad 4-layer PCB (empty for now) |
| Libraries | lib/ — every symbol, footprint and 3D model used on the board |
| Manufacturing, validation, 3D exports | Generated by the CI (KiBot) |
| Documentation sheets | Block diagram, architecture, power sequencing, revision history |
| CI resources | GitHub Actions workflow, KiBot YAML configuration |
DIRECTORY STRUCTURE
.
├─ Computations # Design notes and calculations
├─ HTML # Generated HTML pages
├─ Images # Pictures, renders
│
├─ kibot_resources # External resources used by KiBot
│ ├─ colors # Color themes for KiCad outputs
│ ├─ fonts # Fonts used in generated documents
│ ├─ scripts # Helper scripts used with KiBot
│ └─ templates # Templates for KiBot reports (this README: readme.txt)
│
├─ kibot_yaml # KiBot YAML configuration files
├─ KiRI # KiRI PCB diff viewer files
│
├─ lib # Project libraries (self-contained)
│ ├─ lib_sym # OPEN_TEMP.kicad_sym — every symbol used
│ ├─ lib_fp # OPEN_TEMP.pretty — every footprint used
│ └─ 3d_models # STEP models referenced by the footprints
│
├─ Logos # Project logos
│
├─ Manufacturing
│ ├─ Assembly # BoM, position files, assembly notes
│ └─ Fabrication # Gerbers, drill tables, fabrication notes
│
├─ Reports # ERC / DRC reports
├─ Schematic # Exported schematic PDFs
├─ Templates # Drawing sheets and title block templates
└─ Testing
└─ Testpoints # Test point tables
DEVELOPMENT WORKFLOW
This project uses a reproducible hardware workflow based on KiCad 10, KiBot and GitHub Actions.
The CI pipeline (.github/workflows/ci.yaml) runs KiBot on every push to dev or main and commits the generated outputs back ("Update Outputs" commits). Always git pull after the CI has run, before editing the project again, otherwise the regenerated files (.kicad_pro, BoM, netlist, README…) will conflict.
ℹ️ README.md is generated by KiBot from kibot_resources/templates/readme.txt. Edit the template, not README.md, or your changes will be overwritten by the next CI run.
Branch convention: dev is the development branch; main only receives merges from dev and carries the release tags.
Project metadata (project name, board name, company, designer, logo, repository URL) is defined once in kibot_yaml/kibot_main.yaml (definitions: section) and propagated to title blocks, documents and this README.
When the PCB has an outline and placed parts: switch kibot_variant to PRELIMINARY in ci.yaml and uncomment the 3D renders at the top of readme.txt.
Release a new hardware revision:
- On
dev, fill the [Unreleased] section of CHANGELOG.md.
- Switch
kibot_variant to CHECKED in ci.yaml once ERC and DRC are clean.
- Merge
dev into main: git checkout main && git pull && git merge dev && git push
- Tag with a plain semantic version (no
v prefix): git tag 1.0.0 && git push origin 1.0.0
- Re-sync
dev: git checkout dev && git merge main
CHANGELOG
See CHANGELOG.md (Keep a Changelog format, semantic versioning).
LICENSE
The hardware design files in this repository are released under the CERN Open Hardware Licence Version 2 – Permissive (CERN-OHL-P v2). See LICENSE for the full licence text.
Copyright 2026 Dimitry Siebert, OPEN THRUST LAB. Source location: https://github.com/foukouda/OPEN_TEMP.
Under CERN-OHL-P v2:
- You may use, study, modify and manufacture this design freely
- Derivative works do not need to remain open source
- Modified files must carry a notice stating that they were modified, with the date and a short description of the changes
- The original copyright and licence notices must be preserved
- The design is provided "as is", without any warranty (section 5 of the licence)
The KiBot configuration and CI workflow come from the KDT_Hierarchical_KiBot template by Nguyen Vincent (MIT licence).
For more on CERN-OHL licences: cern-ohl.web.cern.ch
