Helping Hand LED Ring
A custom ring of LEDs built to fit inside a helping hands magnifying glass.
I designed a PCB that fits around the inside of my helping hands magnifying glass. It carries 32 surface-mount LEDs and a three-position switch that selects one of three brightness levels.
Three brightness levels
I started with a test circuit on a breadboard. I wanted adjustable brightness, and the simplest way I found was to light one third, two thirds or all of the LEDs. A three-way switch and two zener diodes handle the switching.
Circuit design
Once the breadboard version worked, I drew up the circuit diagram in KiCad so it could become a proper PCB.
Fitting the glass
I measured the inner diameter of the magnifying glass and chose an inner diameter for the ring that would not cover much of the lens.
I did not have any SMD resistors on hand, so I used through-hole resistor footprints that allow the resistors to be mounted at a 45 degree angle. SMD resistors would have been the better choice.
Build photos
