Low power Hall effect sensor for battery powered security systems

In the past, I made several battery powered modules with a reed contact to detect the opening of a door or window. These work well, but are not very reliable in the long run. So, I got the idea to replace the reed contacts with a Hall effect sensor, which are cheap nowadays, and available in abundance.

The most well-known Hall effect sensor in the Arduino world is the A3144 from Allegro, since it is often used in Arduino modules, like the KY-003. Allegro specifies for the A3144 a power supply voltage of 4.5 to 24 Volt, and a supply current of 4.4 to 9.0mA. This is not very useful for battery powered systems.

My search for a low power Hall effect sensor lead to the SL353LT from Honeywell: it consumes on average 1.8µA and works from 2.2V. Far better for battery powered applications!

There are probably others too, but this one is cheap and available.

SOT23-3 pinout

Pin Function



For comparison: A3141.pdf

Supply Voltage

My measurements reveal that the SL353LT still functions correctly down to a Voltage of 2.0 Volt.


I used the SL353LT to replace the reed contact in all my WindowOpenSensor.

The advantage of the Hall-effect sensors:

  • the are much more sensitive, so the magnet does not have to be so close
  • they are less direction-sensitive
  • the do not break so easily