# A3144 Hall effect sensor: specs and pinout

> The chip is the Allegro A3144, a unipolar Hall-effect switch (Allegro lists it as discontinued); the module chip on the listing board is not…

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The chip is the Allegro A3144, a unipolar Hall-effect switch (Allegro lists it as discontinued); the module chip on the listing board is not verified. The output turns on when a magnet of the right polarity gets close and releases when it moves away.

Every value cites its sourceChip-level pinout

[Buy on Compoden](https://compoden.com/products/a3144-hall-effect-sensor-module-unipolar-magnetic-switch)

## Specs

| Spec | Value | Source |
|---|---|---|
| Supply voltage VCC | 4.5 V to 24 V (abs. max 28 V) | source Features and Absolute Maximum Ratings (PDF p.2); Electrical Characteristics (p.3) |
| Output | Open collector, sinks up to 25 mA | source Features (PDF p.2) |
| Output saturation voltage | 175 mV typical, 400 mV max at IOUT 20 mA, B above BOP | source Electrical Characteristics (PDF p.3) |
| Output leakage current | 10 uA max at VOUT 24 V, B below BRP | source Electrical Characteristics (PDF p.3) |
| Operate point BOP (A3144) | 70 to 350 gauss at 25 C | source Magnetic Characteristics (PDF p.3) |
| Release point BRP (A3144) | 50 to 330 gauss at 25 C | source Magnetic Characteristics (PDF p.3) |
| Hysteresis (A3144) | 20 gauss minimum, 55 gauss typical | source Magnetic Characteristics (PDF p.3) |
| Supply current | 4.4 mA typical, 9.0 mA max, output off | source Electrical Characteristics (PDF p.3) |
| Operating temperature | -40 C to +85 C (E suffix); -40 C to +150 C (L suffix) | source Absolute Maximum Ratings (PDF p.2) |

## Power

| | Value | Source |
|---|---|---|
| Supply | 4.5 V to 24 V (chip) | source Electrical Characteristics (PDF p.3) |
| Current | 4.4 mA typical, output off | source Electrical Characteristics (PDF p.3) |

## 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.

These are the 3 leads of the Allegro chip. The module board (any pull-up, comparator, indicator LED, header order) is not covered by an official document; check which rail your module pulls the output up to before connecting a 3.3 V input.

| Pin | Function | Voltage | Notes | Source |
|---|---|---|---|---|
| 1 | SUPPLY (VCC) | 4.5 V to 24 V | Pinning shown viewed from branded side | source PDF p.2 |
| 2 | GROUND | 0 V | | source PDF p.2 |
| 3 | OUTPUT | open collector | Sinks up to 25 mA; needs pull-up | source PDF p.2 |

## Build with it
Project ideas for the A3144 Hall effect sensor. Each link opens Soldr with the prompt filled in; Soldr assigns the pins, checks power and shows how to wire every part.

- [Wheel speed counter](https://app.soldr.ai/?prompt=I%20want%20to%20build%20a%20wheel%20RPM%20counter%20with%20an%20Arduino%20UNO%20R4%20WiFi%2C%20an%20A3144%20Hall%20sensor%20module%2C%20a%20small%20magnet%20and%20a%2016x2%20I2C%20LCD): A 5 V board meets the chip's 4.5 V minimum supply and counts one pulse per magnet pass.
- [Lid-open detector](https://app.soldr.ai/?prompt=I%20want%20to%20build%20a%20box%20lid%20open%20detector%20with%20an%20ESP32%2C%20an%20A3144%20Hall%20sensor%20module%2C%20a%20logic%20level%20converter%20and%20an%20OLED%20display): The sensor module is undocumented, so power it from 5 V and send its output through the 2-channel level converter (5 V side to the module, 3.3 V side to the ESP32) instead of assuming a pull-up level. Learning project.
- [Fan speed readout](https://app.soldr.ai/?prompt=I%20want%20to%20build%20a%20fan%20speed%20readout%20with%20an%20Arduino%20UNO%20R4%20WiFi%20and%20an%20A3144%20Hall%20sensor%20module%20that%20counts%20a%20magnet%20on%20a%20fan%20blade): One magnet gives one pulse per turn; keep the magnet small so the blade stays balanced.
- [Magnet-triggered buzzer](https://app.soldr.ai/?prompt=I%20want%20to%20build%20a%20magnet-triggered%20buzzer%20with%20an%20ESP32%2C%20an%20A3144%20Hall%20sensor%20module%2C%20a%20logic%20level%20converter%20and%20an%20active%20buzzer): The chip's output is open collector and pulls low when a magnet is near. The module is undocumented, so route its output through the level converter before the ESP32 input.

## Common mistakes

- Do not run the bare chip from 3.3 V: the sheet says VCC operation starts at 4.5 V. Power it from 5 V and pull the open-collector output up to your logic level (source: [link](https://www.allegromicro.com/-/media/files/datasheets/a3141-2-3-4-datasheet.pdf), PDF p.2).
- The output is open collector, so it needs a pull-up resistor; without one it never goes high (source: [link](https://www.allegromicro.com/-/media/files/datasheets/a3141-2-3-4-datasheet.pdf), PDF p.2).
- It is unipolar: it is the magnetic field polarity and strength that switch it, so a magnet turned the wrong way may do nothing (source: [link](https://www.allegromicro.com/-/media/files/datasheets/a3141-2-3-4-datasheet.pdf), description, PDF p.2). Allegro lists the part as discontinued, so module behaviour may differ.

## Not covered by the official source

- Allegro marks the A3144 discontinued (Oct 2005) and recommends the A1104; the module's actual chip is not verified.
- Module board not documented by an official source.

## Sources

- [link](https://www.allegromicro.com/-/media/files/datasheets/a3141-2-3-4-datasheet.pdf) (A3141-A3144 Sensitive Hall-Effect Switches, Allegro 27621.6B; discontinued product)