Here is a simple general-purpose security alarm circuit built on the Arduino platform. It brings up an obtrusive alert signal when an intrusion/theft attempt is observed by its front-end sensor. In ...

There are two sensor choices, reed and Hall-effect switches. They have many similarities but also significant differences, explains Martin Reizner. Demand for reed switches has risen significantly in ...

All credit to Thomas Langewouters for an unusual reed switch ladder circuit for liquid level sensing. You can find it on his website here. He went on to use a more traditional two-terminal design, but ...