SII (Seiko Instruments Inc.) semiconductor developed a new magnetic sensing device "S-5718" which is based on hall effect technology.
Here is the quick description of the device.
"This IC, developed by CMOS technology, is a high-accuracy Hall effect IC with switchable detection pole function that operates at a low voltage and low current consumption.
The output voltage changes when this IC detects the intensity level of magnetic flux density of the polarity according to the input pin status. The inclusion of a switchable detection pole function makes it possible to reduce the number of parts and realize a variety of different systems by using this IC with a magnet. High-density mounting is possible by using the super small SNT-4A package.
Due to its low voltage operation and low current consumption, this IC is suitable for battery-operated portable devices. Its high-accuracy magnetic characteristics also allow this IC to reduce operation dispersion in magnet combination systems."
What is different from the previous their hall sensors is that this chip actually supports 3 state detection. The conventional hall effect switch ICs are capable to distinguish only 2 states. The conventional hall effect switch ICs are fixed configuration and detect only the presence or absence of an N pole or S pole.
This new chip is able to detect N poles, S poles, and both poles which means it can distinguish 3 states with a single IC, N pole in proximity, S pole in proximity, and no magnet.
In their article, it explains the possible IoT applications using this 3 state hall effect switch IC.
The one of the examples they mention in the article is to monitor the opened/closed states of patient room doors could be made to distinguish three states instead of just closed or opened states and send alerts. Before a door is opened so that a person can pass through, an alert could be sent to the smartphones of the nurses over Wi-Fi or Bluetooth.
The chip is available through their sales but I am not sure if the evaluation board is available.
I think having 3 state with low power is good features to the IoT applications such as the monitoring system even the personal belongings like luggage/bag.
Tiny gadget might be very useful and it is probably fun to build such a DIY device.
I personally think it can be used for board game to track the progress of the players.