Build your own waterproof Umbilical Torch

 

After doing some research and looking at several other web pages and designs for a DIY scuba torch, i decided that i wanted to build an umbilical torch. The hardest part seemed to be how to make the lighthead itself. I found the UKRS webpage a great help, this web page also suggested using a pond lamp for the lighthead as they are already built to be waterproof, and most run on 12V. I managed to find the pond lamp shown below in a market in Thailand for £5 while on holiday!

 

For the battery pack, which would be attached to my BCD or tank, I wanted a tube that i could attach jubillee clips to and that could take some knocks. I had some suggestions about encasing the whole battery pack in sealant to make it watertight, but wasn't sure if this would hold the batteries firmly enough. The metal tube shown below was found at the local tip. I have no idea what it was from originally. Other options for tubes could be old fire extinguishers etc.

Again from information from the UKRS webpage, I decided to run the lamp at slightly over 12V by using 12 x 1.2V 4000mAh NiMH batteries with tabs. I bought these batteries from Strikalite and soldered them into a big battery of 14.4V and 4Ah, which can be seen below in its soldered state. The batteries cost around £52.

 

Now to build the waterproof casing to hold the batteries. To seal the ends of the tube, i decided to use a load of epoxy glue. Placing the tube on a sheet of aluminium foil, and then on a flat surface, in my case a piece of glass. The glue and hardener were poured into the tube, in equal quantities and the stirred gently with a long thin piece of wood.

 

After the epoxy was allowed to set, some of the epoxy had leaked out from the end of the tube, so i cut off the burrs, and sanded the end flat.

 

The Bulgin Bucaneer connectors are easy to wire to the cables as they require no soldering. I then inserted the batteries into the tube, and filled the tube with water proof silicone sealant to prevent water ingress. The end was then sealed off in a similar method to the other end.

 

Building the Battery charger: The battery charger simply consists of a constant volt (24V) dc power supply which came from RS, with a 15W, 68 Ohm resistor wired in series with the DC output. This resistor knocks the current down to around C/10 for an extremely simple constant current charger. However, I need to add a timer switch to the plug end to prevent overcharging.

 

The finished item can be seen below. I've added clips so that it can be attached easily to my BCD. I still need to build an easy to hold handle for the lamp head though. This torch has currently been tested to a depth of 11m. I'll test it in a deeper as soon as the opportunity arises.