Summary

Building the Solar Flashlight Blinky
Charles Shapiro
19 Jan 2026

This is a modification of the Gamasonic solar-powered keychain
flashlight which replaces the original case and pushbutton switch with
a new case, a toggle switch, and two RGB LED blinkies. This makes it
useful as a bike or running light. After approximately a 2-hour
charge in full sun, the lights should blink for about 2 hours. They
will go at pretty much full power until the last 15 minutes or so, at
which point they'll quickly degrade to only fading red pulses.

A crate of over 500 of these flashlights turned up at my local
makerspace. None of them would light, but we soon found that the only
defect was the pushbutton. The solar cells, batteries, and LEDs all
worked fine.

Materials:

3D printed box and lid (STL s included ) I printed mine in Natural PLA
with a 0.6mm nozzle on a Prusa MK4S.

Subminiature panel mount SPDT toggle switch with 6 mm (1/4")
shaft. Adafruit sells this one ( https://www.adafruit.com/product/3221
)

Two pieces of 0.34 mm (22 gauge) hookup wire, about 7.5 cm long

Two 5mm RGB LED blinkies. I used these (
https://www.amazon.com/dp/B08ZY5L6S3 )

Rosin core electronic solder and soldering iron

Solder sucker or solder wick

J000 screwdriver

Needlenose pliers

Steps:

1. Dissect the flashlight out of its plastic case. Four screws hold
   the case together. They are tiny phillips head screws. A J000 (1.5
   mm) bit or screwdriver will fit them. Go gently or you risk
   stripping the heads. After you remove the screws, the case will divide
   in half and you can remove the flashlight in one piece. Save the screws!

2. Remove the pushbutton switch from the circuit board. The easiest
   way to do this is to lay the hot end of your soldering iron across the
   two legs of the switch along the long axis of the flashlight and grasp
   the switch with a pair of tweezers. Pry those two legs loose from
   their pads, then heat the opposite side in the same way to remove the
   button. Verify that the flashlight works by shorting a top pad with a
   bottom pad. You should see a small flash in the LEDs. If you don't,
   try charging the light briefly under an incandescent bulb.

3. Remove the LEDs from the top of the board. They actually go into
   through-holes with solder pads; once the LEDs are out, you may have to
   use a solder sucker or wick to expose these holes. Don't overheat
   or force things, or the solder pads will lift off the board.

4. Insert the blinkies into the through holes from the side of the
   board with the solar cell. Make sure that the flattened side of the
   LED ( the short lead) is to the outside, furthest from the
   batteries. Carefully solder the 4 leads in.

5. Solder in the switch. Strip about 2 mm of insulation from one end
   of your wires, and about 4 mm from the other end. Tin both ends. The
   pushutton shorts between the pads on the long axis of the flashlight,
   so you will need to solder one wire to a pad farthest from the LED
   lights, and another wire to a pad nearest to the LED lights. Be
   careful not to solder bridge the pads, or you'll have a light that
   won't turn off. Bend the other ends of the wires into hooks and
   solder them to the switch, one to the center tab and one to either
   one of the edge tabs.

If you've done this right, the blinkies should flicker red when you flick
the switch one way, and off when you flick it the other way. If it
doesn't turn on, try charging it under an incandescent light for
around 20 minutes before deciding you have made a mistake.

1. Insert the board into the box solar cell up.

2. Insert the toggle switch into the hole at the bottom of the box
   from inside, put the lock washer on the outside, then tighten the nut
   on with a pair of needlenose pliers.

3. Screw the lid on with the four screws salvaged from the original
   flashlight. I like to add a bit of plastic wrap between the lid and
   the box for some waterproofing; YMMV on this.

4. Charge for about 2 hours in bright sunlight, and enjoy!