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 ...

The circuit consists of two MOSFETs connected through positive feedback to form a one-shot timer (see the figure). The circuit operates as follows: When the switch closes, the gate of Q2 is pulled ...

He built a simple Arduino-driven MOSFET circuit to deliver knocks of variable BPM to the sound-board of a ukulele.