A3144 Hall Effect Switch Sensor – TO-92, 4.5V–24V

A3144 Hall Effect Switch Sensor - TO-92, 4.5V to 24V

$0.75 NZD
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A3144 Hall Effect Switch Sensor – TO-92, 4.5V–24V
  • A3144 Hall Effect Switch Sensor – TO-92, 4.5V–24V
  • A3144 Hall Effect Switch Sensor – TO-92, 4.5V–24V
  • A3144 Hall Effect Switch Sensor – TO-92, 4.5V–24V
  • A3144 Hall Effect Switch Sensor – TO-92, 4.5V–24V
  • A3144 Hall Effect Switch Sensor – TO-92, 4.5V–24V
  • A3144 Hall Effect Switch Sensor – TO-92, 4.5V–24V
A3144 Hall Effect Switch Sensor - TO-92, 4.5V to 24V
SKU: A3144-HALL-TO92

A3144 Hall Effect Switch Sensor - TO-92, 4.5V to 24V

$0.75 NZD
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The A3144 is the workhorse hall effect switch: bring a south pole near its marked face and the output pulls LOW, take the magnet away and it releases again. It is unipolar, so a north pole does nothing at all, which is the single most common reason one appears dead on the bench. Runs on anything from 4.5V to 24V, so it drops straight into 5V logic, 12V and 24V systems alike.

  • Digital on/off output, not a field measurement
  • Unipolar: only a south pole triggers it
  • Releases as soon as the magnet leaves
  • Wide 4.5V to 24V supply range
  • Open collector output, needs a pull-up
  • Reads LOW when a magnet is detected
  • Fast switching, no contact bounce
  • Works with Arduino, ESP32 and Raspberry Pi
  • TO-92 package, breadboard friendly
  • Marked “3144 609” on the flat face

How it works

Specifications

Model A3144, marked “3144 609”
Sensor type Unipolar hall effect switch
Supply voltage 4.5V to 24V DC
Output type Digital, open collector (active low)
Output state LOW while a south pole is present, HIGH otherwise
Magnetic polarity South pole on the marked face triggers it. North does nothing.
Pull-up resistor Required, or use the microcontroller's internal pull-up
Response Fast switching, no mechanical bounce to debounce
Package TO-92, 3-pin, 1.27mm lead pitch
Pinout Marked face toward you, legs down: 1 VCC / 2 GND / 3 OUT
Sensing face Flat (marked) face of the TO-92 body
Operating temp -40°C to +85°C
Body size Approx. 4.1mm wide, 4.0mm tall, leads 13.5mm+
SKU A3144-HALL-TO92

Wiring & getting started

  1. Hold the sensor with the flat marked face toward you, legs pointing down. Pins 1, 2, 3 run left to right.
  2. Pin 1 -- VCC: anywhere from 4.5V to 24V. On an ESP32 use the 5V rail, not 3.3V.
  3. Pin 2 -- GND: common ground of your circuit.
  4. Pin 3 -- OUT: to a digital input, with a pull-up. pinMode(pin, INPUT_PULLUP) saves fitting a resistor.
  5. Read it inverted: digitalRead(pin) == LOW means a magnet is detected. HIGH means none.
  6. If nothing happens, turn the magnet around. Only the south pole triggers a unipolar switch.

Great for

RPM and wheel speed

One magnet on a wheel or shaft, counted on an interrupt pin, gives clean revolution counting.

Door and lid detection

Non-contact open/closed sensing that will not wear out like a mechanical switch.

3D printer endstops

A contactless replacement for microswitches, unaffected by dust or repeated homing.

Magnetic proximity

Detect presence through plastic, glass or a sealed enclosure wall.

Robotics and automation

Limit detection and index marks where a contact switch would be fragile.

Tamper and reed replacement

A solid-state alternative to reed switches, with no glass envelope to break.

Good to know: the sensing element sits in the flat marked face, not the rounded back, so point that side at your magnet. Small neodymium magnets work far better than flexible fridge magnets, which are often too weak to trigger it. If you need the output to stay on after the magnet leaves, you want a latch such as the 41F or US1881 instead. Shipped from our Te Awamutu stock.
Related guide Hall Effect Sensors Explained: Switch vs Latch vs LinearSwitch, latch or linear? A plain-English guide to picking the right hall effect sensor for your Arduino or ESP32 project, with wiring, code, and fixes for th...

Frequently Asked Questions

Answers to the questions buyers ask most.

Does it matter which way round the magnet is?
Yes, and this is the number one reason an A3144 seems dead. It is a unipolar switch, so only a south pole facing the printed flat side will trigger it. Turn the magnet over and nothing happens at all. If your circuit looks right but nothing responds, flip the magnet before you suspect anything else.
Why does the output flicker or react to my hand?
The output is open collector, which means it can only pull down to ground and cannot drive itself high. Left unconnected it floats and picks up noise. Add a 10k resistor from OUT to VCC, or just let the microcontroller do it with pinMode(pin, INPUT_PULLUP) and no extra parts.
Should the pin read HIGH or LOW when a magnet is near?
LOW. The output pulls to ground when it detects, so the logic runs backwards from what most people expect. LOW means magnet detected, HIGH means no magnet.
Can I run it from 12V or 24V?
The sensor itself is happy anywhere from 4.5V to 24V, so it drops straight into automotive and 24V systems. One important detail: pull the output up to your logic rail, not to 24V. Because it is open collector you can power the sensor from 24V and still pull OUT up to 5V or 3.3V, which is exactly what you want feeding a microcontroller.
Will it work with a 3.3V ESP32?
It needs at least 4.5V to run, so power it from the 5V pin rather than 3.3V. The open collector output then lets you pull up to 3.3V, so the ESP32 only ever sees a safe 3.3V logic level. No level shifter needed.
How close does the magnet have to be?
With a small neodymium magnet you can usually expect somewhere between a few millimetres and about a centimetre, depending on the magnet's size and grade. Fridge magnets are often too weak to trigger it at all. If you need to sense across a wider gap, the OH137 is the more sensitive part.
Does it stay on after the magnet leaves?
No. The A3144 is a switch, so it releases as soon as the magnet moves away. If you want one that holds its state until it sees the opposite pole, you want a latch such as the 41F or US1881.

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