2 layers49 × 50.4 mm
4 layers70 × 45 mm
Mini dyno
EhlOps/mini-dynoThe mini dyno (dynamometer) is a tool created to measure the torque and power output of an engine or motor. The mechanical portion of the dyno functions as a water brake.
- Size
- 70 × 45 mm
- Copper layers
- 4
- Thickness
- 1.6 mm
- Parts
- 58
- Nets
- 72
- Pads
- 234
- Tracks, vias
- 284, 147
- Pours
- 4
- Routed
- Yes
- KiCad
- KiCad 10.0 (file 20260206)
- Created
- 12 Dec 2025
- Updated
- 27 Sep 2026
Overview
Mini dyno is an open-source printed circuit board by EhlOps, from the EhlOps/mini-dyno repository on GitHub, published under the CERN-OHL-P-2.0 licence. It is a 4-layer board of 70 × 45 mm with 58 parts on 72 nets, routed with 284 tracks and 147 vias.
It is built around the ESP32-C3-MINI-1, HX711 and AZ1117IH-3.3TRG1, with the TPD2S017DBV, 916-252A2023Y10200 and AO3400A among its other parts. Its parts include 20 resistors, 12 capacitors, 4 ICs, 4 diodes and 2 connectors. It belongs with the ESP32 and RISC-V boards of this library.
Main components
7ESP32-C3-MINI-1
--40℃~+81℃ -89dBm 2.4GHz 350mA 3V~3.6V 82mA ESP32-C3 Chip On-board PCB Antenna UART - WiFi Modules ROHSRF CrazyWiFi Modules
HX711
SOP-16-40℃~+85℃ 1.4mA 10Hz、80Hz 1MHz~20MHz、11.0592MHz 2 2.6V~5.5V 20mV、40mV、80mV 24 Built-in External、Built-in SPI Support Yes SOP-16 Analog to Digital Converters (ADC) ROHSAvia SemiconAnalog To Digital Converters (ADC)
AZ1117IH-3.3TRG1
SOT-223-40℃~+125℃@(Tj) 1 1.3V@(0.8A) 15V 3.3V 4mA 70dB@(120Hz) Fixed Over Current Protection、Over Temperature Protection Positive SOT-223 Voltage Regulators - Linear, Low Drop Out (LDO) Regulators ROHSDiodes IncorporatedUncategorised
TPD2S017DBV
SOT-23-6-40℃~+85℃ 12V 1pF 2 6V Bidirectional ESD IEC 61000-4-2 SOT-23-6 ESD and Surge Protection (TVS/ESD) ROHSTexas InstrumentsESD And Surge Protection (TVS/ESD)
916-252A2023Y10200
插件-55℃~+85℃ 1 1,500 Cycles、5,000 times 13.7mm 4P Black Female Through Hole Type-A USB 2.0 插件 USB Connectors ROHSJing Extension of the Electronic Co.USB Connectors
AO3400A
SOT-23-55℃~+150℃ 1 N-channel 1.45V 1.4W 30V 48mΩ@2.5V 5.7A 50pF 630pF 75pF 7nC@10V N-Channel SOT-23 MOSFETs ROHSAlpha & Omega SemiconductorMOSFETs
USB4085-GF-A
插件-40℃~+85℃ 1 48V 5A Black Female Right Angle Type-C USB 2.0 插件 USB Connectors ROHSGlobal Connector Technology (GCT)USB Connectors
README
README.mdMini Dyno
Overview
The mini dyno (dynamometer) is a tool created to measure the torque and power output of an engine or motor. The mechanical portion of the dyno functions as a water brake. This design is suited for engines up to 4 horsepower and is mainly used to measure the output of small engines used in RC cars.
An ESP32-C3 microcontroller reads a load cell (via HX711 ADC) and a Hall effect RPM sensor, converts the readings to torque (Nm) and RPM, then streams them over WiFi to an iOS companion app. The app plots a traditional dyno graph — torque and power vs RPM — in real time.
System Architecture
Engine ──── Water Brake ──── Load Cell ──── HX711 ────┐
│ ESP32-C3 ── WiFi AP ── iPhone
Hall Sensor (4 magnets/rev) ─────────────┘| Measurement | Sensor | Pin |
|---|---|---|
| Force (→ Torque) | HX711 load cell ADC | PD_SCK: GPIO 7, DOUT: GPIO 6 |
| RPM | Digital Hall effect | GPIO 10 |
| Ready indicator | LED | GPIO 5 |
Torque arm: 100 mm (load cell to shaft centre)
Torque (Nm): Force (N) × 0.1 m
Power (hp): Torque (Nm) × RPM × 2π / 60 / 745.7
Repository Structure
mini-dyno/
├── firmware/ — ESP-IDF project for ESP32-C3
└── software/ — iOS companion app (Xcode / SwiftUI)See the README in each subdirectory for build and usage instructions.
Parts
58| Qty | Value | Footprint | References |
|---|---|---|---|
| 6 | 10uF | Capacitor_SMD:C_0805_2012Metric | C1, C2, C4, C5, C7, C10 |
| 5 | 0.1uF | Capacitor_SMD:C_0805_2012Metric | C3, C6, C8, C11, C12 |
| 5 | 10kΩ | Resistor_SMD:R_0805_2012Metric | R9, R10, R12, R14, R15 |
| 4 | 0Ω | Resistor_SMD:R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R3, R6, R7, R13 |
| 4 | 5.1kΩ | Resistor_SMD:R_0805_2012Metric | R1, R2, R18, R19 |
| 4 | ~ | MountingHole:MountingHole_3.2mm_M3_Pad | H1, H2, H3, H4 |
| 3 | 100Ω | Resistor_SMD:R_0805_2012Metric | R4, R5, R11 |
| 2 | 1MΩ | Resistor_SMD:R_0805_2012Metric | R8, R20 |
| 2 | 1kΩ | Resistor_SMD:R_0805_2012Metric | R16, R17 |
| 2 | SW_Push | Button_Switch_SMD:SW_Push_1P1T_NO_E-Switch_TL3301NxxxxxG | Boot, Reset |
| 1 | 1uF | Capacitor_SMD:C_0805_2012Metric | C9 |
| 1 | 3V3 | TestPoint:TestPoint_THTPad_2.0x2.0mm_Drill1.0mm | TP3 |
| 1 | 5V | TestPoint:TestPoint_THTPad_2.0x2.0mm_Drill1.0mm | TP2 |
| 1 | 916-252A2023Y10200 | easyeda2kicad:USB-A-TH_916-352A102BY10200 | MOTOR1 |
| 1 | AO3400A | Package_TO_SOT_SMD:SOT-23_Handsoldering | Q1 |
| 1 | AZ1117IH-3.3TRG1 | easyeda2kicad:SOT-223-4_L6.5-W3.5-P2.30-LS7.0-BR | U1 |
| 1 | Conn_01x03_Pin | Connector_PinHeader_2.54mm:PinHeader_1x03_P2.54mm_Horizontal | J2 |
| 1 | Conn_01x04_Pin | Connector_PinHeader_2.54mm:PinHeader_1x04_P2.54mm_Horizontal | J1 |
| 1 | DATA | easyeda2kicad:USC-C-SMD_USB4085-GF-A | USB2 |
| 1 | D_Schottky | Diode_SMD:D_SMB | D2 |
| 1 | D_TVS | Diode_SMD:D_SMB | D1 |
| 1 | ESP32-C3-MINI-1 | PCM_Espressif:ESP32-C3-MINI-1 | U3 |
| 1 | GND | TestPoint:TestPoint_THTPad_2.0x2.0mm_Drill1.0mm | TP5 |
| 1 | HX711 | easyeda2kicad:SOP-16_L10.0-W3.9-P1.27-LS6.0-BL | U2 |
| 1 | LED_ON | LED_THT:LED_D5.0mm | D3 |
| 1 | LED_STATUS | LED_THT:LED_D5.0mm | D4 |
| 1 | MOTOR | TestPoint:TestPoint_THTPad_2.0x2.0mm_Drill1.0mm | TP4 |
| 1 | POWER | easyeda2kicad:USC-C-SMD_USB4085-GF-A | USB1 |
| 1 | Polyfuse | Fuse:Fuse_0805_2012Metric_Pad1.15x1.40mm_HandSolder | F1 |
| 1 | TPD2S017 | Package_TO_SOT_SMD:SOT-23-6 | U4 |
| 1 | VBUS | TestPoint:TestPoint_THTPad_2.0x2.0mm_Drill1.0mm | TP1 |
Questions
How big is the Mini dyno PCB?
It measures 70 × 45 mm and has 4 copper layers, 1.6 mm thick.
What parts does the Mini dyno use?
58 parts, built around the ESP32-C3-MINI-1, HX711, AZ1117IH-3.3TRG1 and TPD2S017DBV. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.
Where can I download the Mini dyno KiCad files?
From the EhlOps/mini-dyno repository on GitHub, at the commit this page was made from: the board is electronics/board/mini-dyno/mini-dyno.kicad_pcb and its schematic electronics/board/mini-dyno/mini-dyno.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the Mini dyno design in my own project?
Its repository publishes it under the CERN-OHL-P-2.0 licence: you may reuse it on that licence's terms (keep the author's notice, and for a copyleft licence share your changes alike).
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