LED torch, USB charge lamp high/low power

Plenty of torches around, but none can beat the DIY one ! With two power stages, it competes with car headlight when on full power, but can shine on for days in spare mode.

Part list: 40mm parabolic mirror, Cree LED 3W or 5W, two switches, round 40mm watch glass, 18650 Lithium battery, aluminium tube 22mm / 20mm, resistors 1.5 ohm 47 ohm, micro USB charger circuit 1N4148 5.1ohm , 3D print cone and plug.

After printing the cone and plug in 3D (PLA shrink 4% taken into account) it should perfectly fit a 22mm outside / 20mm inside tube.

1. Start with the tube, old tent pole is best. Cut 115mm, drill two 8mm holes 15mm from end and polish the tube with fine sandpaper while rotated slowly in lathe or drill.
2. Solder wires on LED and check that it works. Keep solder and wire as thin as possible. Isolate the solder points from the mirror. Glue the LED on the mirror with two-component epoxy. Better wait until the glue sets then mix new epoxy and glue the glass in the mirror too. Too much glue looks ugly, use it sparingly. Do not touch the glass, use pincet.
3. Solder wires on two switches and glue the switches in the tube. With the same mix you could glue the USB adapter in the plug too.
4. I've always used recycled laptop batteries, they may be weak for laptop use but still perfect for a torch and have solderable metal strips. Solder the 1.5 ohm resistor on the + pole of the 18650 battery, solder two wires to resistor. Solder two wires on the - pole as well. For the 5W Cree LED you may use 1 ohm resistor to use its higher power. In this case, glue additional 25x7mm cooling plate (bent aluminium strip) on the rear of the LED (see pictures).
5. Arrange the wires so that each battery end has a + and a - wire. Wrap the battery with isolation tape from all sides. Slide it in the tube, tight fit.
6. Follow the schematics. When all connections ready, test the LED operation and the charging. Voltage drop on the 5.1 ohm resistor should be something like 0.1-0.6V depending on battery charge %.

Admittably the charger circuit is very simple, but since the currents are low, it works without any hazard to LiIon batteries. Charge time : one night, though. If this is too long, you may use a TC4056 charger PCB if you redesign the plug for that. 7. Pull a carry string through the plug hole. Glue the cone, tube and plug together. It is almost watertight now, but don't rely on that, the switch is certainly not. 8. Enjoy !

Parts :

Aluminium mirror https://www.aliexpress.com/item/32909806184.html?spm=a2g0s.9042311.0.0.27424c4dInHx14

Glass 40mm https://www.aliexpress.com/item/32889515650.html?spm=a2g0s.9042311.0.0.27424c4d2kvaRE

Switch 8mm round torch switch https://www.aliexpress.com/item/32869228351.html?spm=a2g0s.9042311.0.0.27424c4dn8YaTc

Cree 3 or 5W LED bead 8mm PCB, micro USB adapter PCB, resistors etc., TP4056 : many dealers on Aliexpress.

Category: Outdoor & Garden