ET-S20
MAX31865 PT100 RTD Amplifier
2/3/4-wire PT100 RTD interface
AED 49.00
Out of stockOverview
2/3/4-wire PT100 RTD interface
The ET-S20 is built around the MAX31865 — 15-bit RTD converter, PT100/PT1000, 2/3/4-wire, fault detection. It connects over SPI (mode 1/3) (≤1MHz through shifters) and is powered from VIN 3.3–5.5V, onboard LDO.
Designed in Dubai by ElectroTrical — the full schematic, BOM and design notes are published below.
Good for
- Precise liquid temperature (brewing, sous-vide)
- Industrial RTD probes
- Lab temperature control
Key features
What makes it different
IC
MAX31865: 15-bit RTD converter, PT100/PT1000, 2/3/4-wire, fault detection
Accuracy
0.03°C resolution; ±0.5°C typ. system with 0.1% Rref
Interface
SPI (mode 1/3), ≤1MHz through shifters
Supply
VIN 3.3–5.5V, onboard LDO
Open documentation
Schematic, BOM and layout notes published for every board.
Breadboard friendly
Standard 2.54 mm pitch and M2.5 mounting holes.
Specifications
Technical specifications
| IC | MAX31865: 15-bit RTD converter, PT100/PT1000, 2/3/4-wire, fault detection |
|---|---|
| Accuracy | 0.03°C resolution; ±0.5°C typ. system with 0.1% Rref |
| Interface | SPI (mode 1/3), ≤1MHz through shifters |
| Supply | VIN 3.3–5.5V, onboard LDO |
| Size | 38.1 × 25.4 mm |
|---|---|
| Mounting | 4 × M2.5 holes, 2.54 mm from each corner |
| Connectors | 8-pin 2.54 mm header · Screw terminal 2P 5.0mm 17A (THT) — RTD terminals F+ / RTD+ (2 of 4) · Screw terminal 2P 5.0mm 17A (THT) — RTD terminals RTD− / F− (3 of 4) |
| Main IC | MAX31865ATP+T (LCSC C118474) |
| Revision | Rev B |
| Libraries | Adafruit_MAX31865 / CircuitPython, ESPHome max31865 |
|---|
| JP1 (default Closed) | Cut to turn off the LED |
|---|---|
| JP3 (default C–B) | ISENSOR: C–B for 2/4-wire, C–A for 3-wire |
| JP4 (default Open) | Bridge for 2-wire: links F+ to RTD+ |
| JP5 (default Open) | Bridge for 2/3-wire: links RTD− to F− |
Performance
How a PT100 responds
Pinout
Pin map and connections
| Pin | Name | Type | Function |
|---|---|---|---|
| 1 | VIN | Power | Power in (3.3–5 V) |
| 2 | 3V3 | Power | 3.3 V regulator output |
| 3 | GND | Ground | Ground |
| 4 | SCK | SPI | ≤1MHz |
| 5 | SDI | SPI | MOSI |
| 6 | SDO | SPI | MISO |
| 7 | CS | SPI | Active low |
| 8 | DRDY | Output | Active low |
Mechanical
Dimensions and what's in the box
In the box
- 1 × ET-S20 MAX31865 PT100 RTD Amplifier (assembled)
- 1 × 8-pin 2.54 mm male header, unsoldered
Getting started
- Wire the header: VIN, 3V3, GND, SCK, SDI, SDO
- Libraries: Adafruit_MAX31865 / CircuitPython, ESPHome
max31865
Compare
Which temperature probe interface?
| MAX31865 PT100 RTD Amplifier (this board)This board | ET-S19 MAX31856 Thermocouple Amplifier | ET-S21 DS2484 1-Wire Hub | ET-S16 TMP117 ±0.1 °C Temperature Sensor | |
|---|---|---|---|---|
| What it does | 2/3/4-wire PT100 RTD interface | Universal thermocouple interface, K/J/N/R/S/T/E/B | I²C to 1-Wire bridge for DS18B20 sensors | Medical-grade accuracy digital temperature sensor |
| Interface | SPI (mode 1/3), ≤1MHz through shifters | SPI (mode 1/3), up to ~1MHz through the BSS138… | I²C fixed 0x18, up to 400kHz | I²C 0x48–0x4B |
| Best for | Precise liquid temperature (brewing, sous-vide) | Kilns, ovens and reflow controllers | Many DS18B20 sensors on one bus | Precision temperature logging |
| Price | 49 AED | 59 AED | 25 AED | 39 AED |
Downloads
Documents and design files
Need a custom version of this board?
Different connector, size or sensor? We design and build custom variants.