Build a divelight !

We are a couple of guys in the club BSMJ (Baltic Sea Mud Jumpers), that have been diving in dark waters, and some times we wanted a good divelight. As the price for commercial lights is very high, we started a project for building a cheaper alternative. Absolute maximum price should be $100:-, preferrably not more than $50:-.

Our goal was to build a lamp with strong light, long burntime, cheap, easy to handle (separate battery and lamphead), and not to hard to build.

After the first tests with a plastic box (save the leftovers), that went pretty well, I got a mail from Fredrik Carlen where he showed me his light. His idea was genial. Allthough Fredrik's cunstruction had some shortcomings that we improved (?) in our version.


We use two 12V 7 Ah "gastight" acks, with a total of 14 Ah that is enough for a 75W for two hours. (could be used in the future for lamps of several 100:s of watts). I had a problem with a small leakage where the o-ring meets the cannister, but solved that with a gasket made of rubber.	The lamphead can be opened for switching lamps. Furthermore we put the power switch in the cylinder. This is because the batteries produce hydrogen when heavily loaded. Hydrogen with a spark from the switch could end up with an explosion.

The power switch is located in the lamphead and consist of a magnet and a reed relay (?not shore about the enlish word), the kind used in home alarm systems. The magnet slides on the screws along the cylinder. The cylindern is glued in the front end and has an o-ring in the back.	All five of us has different configuration for mounting, but my rig is seen here. I have mounted the battery pack hanging of the bolt between the tanks. This way I need less (actualy none at all) lead. A dumpable solution is on its way.
	About the lamp choice it seems like a floodlamp (angle 20-40 degrees) gives the nicest light, the spot (12 degrees) gives a somewhat narrow light and my opinion is that it is not any stronger. Normal halogen bulbs comes in effect from 20W to 75W. (see history below about better light)
All plane acrylic parts are 10 millimeters, while the lamp cylinder is 5 millimeters. We used Acrifix to glue the parts together. It is a kind of floating acrylic. Warning ! We glued outdoors, and allthough there was a light breeze, we were allmost stoned :-)