Solenoid-pulser

Ding!? A solenoid pulser that strikes a desk bell automatically. It stores charge in a capacitor and dumps it into a 12 V solenoid, producing a clean mechanical ding. A working prototype, though it has not been made into a PCB yet.

What's here

• KiCad schematic and render, plus 3D-printed parts: bell holder, solenoid holder, base plate, and an axle spacer
• The circuit is a NE555 one-shot driving a JF-0530B solenoid

How it dings

Push the trigger and the NE555 one-shot pulses the solenoid for about 15 ms. The solenoid hits the bell. A 100 ohm charge resistor limits how often, and a bushing shortens the throw.