Budget dive lamp

[magnusbrodin]

Hello,

First post in this exciting forum :wave:
I´m about to build a dive lamp and are collecting info regarding what parts could be used. So far I think I have decided to go with a Cree XHP70,2 / 12V which will be powered by a MC gel battery in a canister (12V 4Ah) The question is if https://www.banggood.com/DC-DC-5-32...ard-p-1577997.html?rmmds=buy&cur_warehouse=CN could be used as current regulator?
Would it be a better choice to run the 70,2 in 6V instead since the battery will be below 12V after some time using the light?
As I said, my first build so this might be dumb questions but I have the intention to learn.
We have very little, if some at all, resellers of this kind of electronics in Sweden and our postal/tax system makes even the cheapest item expensive in the end and that's one thing that complicates the build.

Best Regards Magnus

 

[DIWdiver]

Yes, that SHOULD work. You may find that the regulator is overrated, and if you try to run it at 4.8A, it may not last long.

Running the LED at 6V would give you uniform light throughout the run, then rapidly drop to nothing. Some people like this, some would rather have more warning (and actually a longer run). Your choice.

The other thing to wonder about is how much 'overhead' that regulator has. It says 5-32V input, and 0.8-30V output. The max output is 2V lower than the max input. That might well mean that the regulator can't drive the output higher than 2V less than the input. This would be a 2V overhead on the regulator (which wouldn't be surprising).

Scratch that. I looked up the data sheet for the chip that's on there, and it looks like the overhead would be 0.2-0.25V at 2.4A, about double that at 5A, but in that configuration you don't care much. It looks like it might even do okay at 5A, if they use genuine parts.

 

[magnusbrodin]

Thank you for fast and informative answer. Think I will buy this regulator and run 70.2 at 12V at first to try it out. Will have to build head that is possible to open if I would like to change to 6V later on. First thought was to build glued head.
Regarding genuine parts is where it gets questionable, I am sceptic to most ebay, aliexpress and bangood products but at this price it might be worth a test. Other more reliable sources i have found will be ten times as expensive when arrived in Sweden :mecry:

 

[magnusbrodin]

While waiting for my regulator (actually ordered two just in case) I did some research and found an excellent page when it comes to components https://www.electroschematics.com/dc-module/ Looks as if it's a good purchase.
Also started to experiment with water safe switch and tried a magnet switch originally used in a safe to indicate if door is opened or closed. So far it looks promising, can open and close circuit with the magnet through 5 mm aluminium. Most likely I will have to use a relay to get it to work properly since the cables in the switch are rather thin and I do not know what current the switch itself can handle.
To be continued...

 

[DIWdiver]

My first dive light build used two magnets and three hall sensors so I could rotate one way for UP and the other for DOWN to change brightness.

By the way, I strongly suggest using Samarium Cobalt magnets instead of Neodymium. The latter contain iron, and will rust (yes, even though they are nickel or chrome plated). When they rust, they expand and get weak. Samarium Cobalt will not corrode in seawater, even if unplated.

Magnetic switches are typically reed switches, and are usually designed for very low current. There are lots of schematics around the forum showing how to use a FET and reed switch to control a lamp. FETs are much smaller than relays, usually cheaper, and consume less power.

Another option is a piezo transducer. There's some discussion of those too.

TaskLED sells boards designed for running lamps from magnets and piezo transducers.

 

[magnusbrodin]

Thank you for really good inputs. Will look into possibility to use FET instead of relay. The other day I got informed that my employment is terminated due to very little business. This results in me not being able to use the machines to create head and battery canister as I have planned. Will have to bribe remaining staff with a cake and sneak in to workshop when it is time to shape the details :naughty:

 

[DIWdiver]

Condolences on losing your job. Good luck with getting access to the machines!