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.
| Pin | Function |
|---|---|
| 1 | VCC |
| 2 | GND |
| 3 | OUTPUT |
Supply Voltage
My measurements reveal that the SL353LT still functions correctly down to a Voltage of 2.0 Volt.
Usage
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