ACS712 20A current sensor: specs and pinout
The ACS712 is a Hall-effect linear current sensor IC with an isolated low-resistance conductor, available in a 20 A range version. The listing is a module built on it.
Specs
| Spec | Value | Source |
|---|---|---|
| Supply voltage | 4.5 V to 5.5 V (5.0 V typ) | source Common operating characteristics, p.5 |
| Supply current | 10 mA typ, 13 mA max (VCC 5.0 V, output open) | source Common operating characteristics, p.5 |
| Current sensing range (20A version) | +/-20 A | source Selection guide, p.2; x20A characteristics, p.6 |
| Sensitivity (20A version) | 100 mV/A typ (96 to 104) | source x20A performance characteristics, p.6 |
| Zero-current output voltage | VCC x 0.5 (typ) | source Common operating characteristics, p.5 |
| Total output error (20A version) | +/-1.5 % typ at IP = +/-20 A, 25 C | source x20A performance characteristics, p.6 |
| Bandwidth | 80 kHz (-3 dB) | source Common operating characteristics, p.5 |
| Internal conductor resistance | 1.2 milliohm typ | source Common operating characteristics, p.5 |
| Isolation (pins 1-4 to 5-8), chip level | 2.4 kV RMS minimum (agency rated for 60 s); maximum working voltage for basic isolation 297 VRMS; withstand 420 V peak or DC | source Features, p.1; Isolation characteristics table |
| Operating ambient temperature | -40 C to 85 C | source Selection guide and absolute maximum ratings, p.2 |
| Output load | 4.7 kilohm minimum to GND; 10 nF maximum capacitance | source Common operating characteristics, p.5 |
Power
| Value | Source | |
|---|---|---|
| Supply | 5 V single supply (4.5-5.5 V) | source Common operating characteristics, p.5 |
| Current | 10 mA typ | source Common operating characteristics, p.5 |
Chip pins
These are the pins of the chip on the module, from the chip datasheet. The module's own header may label or expose them differently.
Pins are those of the bare 8-lead SOIC chip. The module board (screw terminals, header order, any filter capacitor) is not covered by an official document.
| Pin | Function | Voltage | Notes | Source |
|---|---|---|---|---|
| 1, 2 IP+ | Terminals for the current being sampled; fused internally | Current path with pins 3 and 4 | source Terminal list, p.4 | |
| 3, 4 IP- | Terminals for the current being sampled; fused internally | source Terminal list, p.4 | ||
| 5 GND | Signal ground terminal | 0 V | source Terminal list, p.4 | |
| 6 FILTER | Terminal for an external capacitor that sets bandwidth | source Terminal list, p.4 | ||
| 7 VIOUT | Analog output signal | VCC x 0.5 at zero current | source Terminal list, p.4 | |
| 8 VCC | Device power supply terminal | 4.5-5.5 V | source Terminal list, p.4 |
Build with it
Project ideas for the ACS712 20A current sensor. Each link opens Soldr with the prompt filled in; Soldr assigns the pins, checks power and shows how to wire every part.
- DC load current meter: Uno has a 5 V analog input that matches the sensor's output range. Keep to low-voltage DC loads.
- Fan overcurrent beeper: Compare the reading against a threshold from your own measurements; the fan has its own supply. Learning project.
- Pump current logger: Pump on its own supply through the relay with the sensor in series on the low-voltage side. At 100 mV/A, a pump drawing a few hundred mA gives only tens of mV (200 mA is 20 mV), which is only a few steps of an Uno 10-bit ADC (about 5 mV per step), so small currents read coarsely; pick a larger load or add amplification. Keep wiring low-voltage.
Common mistakes
- Reading the output with a 3.3 V ADC: the output sits at VCC x 0.5 at zero current and moves 100 mV per amp, so large currents push it above 3.3 V on a 5 V supply (source)
- Powering it above 5.5 V: the recommended supply is 4.5-5.5 V and the absolute maximum is 8 V (source)
- Using the chip or module on mains: the sheet rates the isolation at 2400 VRMS for 60 s but gives only 297 VRMS as the maximum working voltage for basic isolation (UL 62368-1), with 4 mm clearance (source: link, Isolation characteristics table). The isolation of the module board itself is not documented, so do not use this module on mains. General safety note, not from the sheet: mains wiring must be done by a qualified person.
Not covered by the official source
- Chip datasheet only; module resistors, header and terminals are undocumented.
- The module's terminal layout is not documented.
Sources
- link (Allegro ACS712-DS Rev. 22, 13 Feb 2024)