Dive Flashlight DIY

 Constructing a diving flashlight (part 1).

Impression image of the flashlite

This flashlight is constructed from parts that are easy to get as shown in the images below. The body is constructed from an aluminium pipe of 250mm with a 50mm diameter.


The front end is made of PVC fittings. First a 63mm/50mm reducer is glued (epoxy) on the pipe. Next the threaded side of a union part is fixed with PVC solvent cement onto the reducer. The 63mm union was chosen for the size of its opening. A 7mm polycarbonate lens is screwed on to the flange with the gland nut. A rubber O-ring ensures a watertight joint. The original flange counterpart of the union became obsolete.

The lens is made by means of a hole drill with an inside diameter of 80mm. Of course, I removed the center drill. These kind of drills are normally used for drilling holes into gutter for attachment of the drain pipe.

The back end is made with a 50mm slip to thread end point that is covered with a threaded cap. A ring is placed on the aluminium pipe before that the end point is fixed with epoxy glue.

This ring will be used as a part of the on/off switch. The image on the right shows a void at the inside. This void is used as a placeholder for a rare earth magnet. This magnet will actuate two reed switches inside the aluminium pipe. Read on for details.


Next the battery holder is constructed out of four 3/4" pipes, 150mm in length. Long enough to hold 4 x 3 2000mAh Eneloop NiMh rechargeable batteries. These 3/4" pipes fit nicely into the aluminium pipe with an inner diameter of 45mm while the batteries fit nicely into the 3/4" pipes. 

The end points are covered with two FR4 copper clad plates. These plates are also made by using a hole drill. The copper clad is etched after covering the areas for the pads simply with small stickers. You can notice additional incisions in the plates if you look real close. These incisions make the construction less rigid to ensure that the individual battery piles make sufficient contact. This is also realized by soldering embossed pads on the PCB pad. 

The battery pack is kept together with a threaded rod. This is shown in the most right image above. This image also shows the harness that is used to connect the batteries to the electronics.

I am using a Cree XM-L T6 3-LED module as light source. These modules can be sourced from internet. I have got mine from DealExtreme. These modules use 18W of power at maximum output. For this they give a lot of light and a lot of heat. This heat has to be removed. That is why I have chosen aluminium over PVC for the body pipe. The Cree module has a heatsink profile integrated in the body. I have stuffed this profile with aluminium rings with a different inner diameter that matches with the profile of the body. The outer diameter of the rings is about 0.1mm less than the inner diameter of the aluminium pipe. All parts were covered with  a thin film of cooling paste before the whole package was assembled together and pressed into the aluminium pipe. 

Please proceed to part 2.

2012 DevDc