ET-S37
ACS725 ±20 A Current Sensor
Isolated Hall current sensor with 16-bit I²C ADC
AED 49.00
Out of stockOverview
Isolated Hall current sensor with 16-bit I²C ADC
The ET-S37 is built around the Allegro ACS725LLCTR-20AB — ±20A AC/DC Hall, 1.2mΩ path, 66mV/A, ±0.8% typ. It connects over I²C 0x48; raw analog VIOUT also on J3.6 and is powered from VIN 3.3–5.5V, onboard LDO (ACS725 needs 3.0–3.6V).
Two Qwiic / STEMMA QT connectors let you chain it with other boards without soldering, and the 2.54 mm header fits a breadboard.
Designed in Dubai by ElectroTrical — the full schematic, BOM and design notes are published below.
Good for
- Motor current monitoring
- Battery and solar current
- Overcurrent protection
Key features
What makes it different
Sensor
Allegro ACS725LLCTR-20AB: ±20A AC/DC Hall, 1.2mΩ path, 66mV/A, ±0.8% typ
ADC
TI ADS1115 measures VIOUT against a VCC/2 reference (differential) → ratiometric, ~0.6mA resolution at ±2.048V PGA
Interface
I2C 0x48; raw analog VIOUT also on J3.6
Supply
VIN 3.3–5.5V, onboard LDO (ACS725 needs 3.0–3.6V)
Qwiic / STEMMA QT
Two JST-SH connectors plus a 2.54 mm header — 3.3 V and 5 V hosts.
Open documentation
Schematic, BOM and layout notes published for every board.
Specifications
Technical specifications
| Sensor | Allegro ACS725LLCTR-20AB: ±20A AC/DC Hall, 1.2mΩ path, 66mV/A, ±0.8% typ |
|---|---|
| ADC | TI ADS1115 measures VIOUT against a VCC/2 reference (differential) → ratiometric, ~0.6mA resolution at ±2.048V PGA |
| Interface | I2C 0x48; raw analog VIOUT also on J3.6 |
| Supply | VIN 3.3–5.5V, onboard LDO (ACS725 needs 3.0–3.6V) |
| Isolation | Low-voltage DC/AC circuits only (≤30V). Not for mains |
| Size | 38.1 × 25.4 mm |
|---|---|
| Mounting | 4 × M2.5 holes, 2.54 mm from each corner |
| Connectors | 2 × Qwiic / STEMMA QT (JST SH 4-pin) · 7-pin 2.54 mm header · Screw terminal 2P 5.0mm 17A (THT) — Current path IP+ / IP− |
| Main IC | ACS725LLCTR-20AB-T (LCSC C459334) |
| Revision | Rev B |
| Libraries | Adafruit_ADS1X15 / CircuitPython, ESPHome ads1115 |
|---|
| JP1 (default Closed) | Cut to turn off the LED |
|---|---|
| JP2 (default Closed) | Cut to remove the host-side I2C pull-ups |
| JP3 (default 1–2 (3V3)) | BW_SEL: 3V3 = 20kHz (low noise), GND = 120kHz (verify polarity) |
Performance
Output vs current
Pinout
Pin map and connections
| Pin | Name | Type | Function |
|---|---|---|---|
| 1 | VIN | Power | 3.3–5.5V |
| 2 | 3V3 | Power | LDO output |
| 3 | GND | Ground | Ground |
| 4 | SCL | I²C | I²C clock |
| 5 | SDA | I²C | I²C data |
| 6 | VIOUT | Signal | Raw analog: 1.65V at 0A, 66mV/A (3.3V-referenced) |
| 7 | ALERT | Output | ADS1115 ALERT/RDY, host level |
Qwiic / STEMMA QT pins: GND, VIN, SDA, SCL (same on both connectors). I²C pull-ups (10 kΩ) are on the board; cut JP2 to remove them.
Mechanical
Dimensions and what's in the box
In the box
- 1 × ET-S37 ACS725 ±20 A Current Sensor (assembled)
- 1 × 7-pin 2.54 mm male header, unsoldered
Getting started
- Plug in a Qwiic / STEMMA QT cable, or solder the header and wire VIN, GND, SDA and SCL
- Libraries: Adafruit_ADS1X15 / CircuitPython, ESPHome
ads1115 - Run an I²C scanner to confirm the address: 0x48
Compare
Which current and power board?
| ACS725 ±20 A Current Sensor (this board)This board | ET-S07 INA228 85 V Power Monitor | ET-S38 2-Channel CT Clamp Interface | ET-S39 ATM90E32 3-Phase Energy Monitor | |
|---|---|---|---|---|
| What it does | Isolated Hall current sensor with 16-bit I²C ADC | 20-bit current, voltage, power and energy monitor | SCT-013 clamp interface with 16-bit I²C ADC | 3-phase energy metering IC with CT inputs |
| Interface | I²C 0x48; raw analog VIOUT also on J3.6 | I²C 0x40 default; 0x41/0x44/0x45 via JP3/JP4 (16… | I²C 0x48 | SPI (mode 3) on J3. No Qwiic (SPI part) |
| Best for | Motor current monitoring | Battery and solar monitoring | Home energy monitoring | 3-phase energy metering |
| Price | 49 AED | 59 AED | 49 AED | 219 AED |
Downloads
Documents and design files
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