We’re always happy to see hackers inspired to try something different by what they see on Hackaday. TO [SimpleTronic] has a project that will allow you to expand your skills in analog electronics in a really fun way. It is an analog electromagnet pendulum circuit. Whether you’re building it or just studying the schematics, it’s a fun way to review the non-digital side of the craft.
The pendulum is a neodymium magnet on the head of a bolt, suspended from a one foot aluminum chain. Below, a Hall sensor sits on a 1 “diameter electromagnet, with a 6/8” wire wrapped around another bolt. As the pendulum magnet accelerates towards the core of the electromagnet, the Hall effect sensor registers an increase in voltage. The voltage reaches its maximum when the pendulum passes overhead, and as soon as the Hall effect sensor detects the voltage drop, the electromagnet ignites for a moment to propel the pendulum. This circuit has very low power consumption, because the electromagnet is only turned on for about 20ms!
The other main components are an LM358N operational amplifier, a CD4001B quad CMOS NOR gate and an IRFD-120 MOSFET. [SimpleTronic] even took the time to highlight each part of the diagram in order to work through a full explanation.
Ultimately, this analog circuit should help newcomers familiarize themselves with electromagnets so they can take the next logical steps: spool guns and web launchers.