20watt Halogen Canister Torch LED Upgrade

[Magpie]

Whilst waiting for some epoxy to set on my homemade umbilical dive torch I thought I'd finally get round to putting some details about a 7 led upgrade I recently completed. I've had a few pm's about upgrading torches so this may help someone.

The base torch was a 12v 20w MR16 Halogen canister light:

The batteries were shot so I planned to replace them with 18650 Lithiums and got hold of some holders that fitted nicely into the canister with a little bit of attention from my dremel.

You'll also see in that pic the reed switch I used in this build. I attached it to the battery holders inside a bit of thin carbon tube for protection. A couple of rare earth magnets easily activated it through the torch case. The original switch hole in the back of the torch was sealed up so there was no way for water to get in.

Having calculated the battery capacity I decided to use 7 cree xp-g r5 leds, which are capable of over 300 lumens each when driven at 1.2amps. The necessary leds and the optic to go with them were ordered from Cutter in Australia: www.cutter.com.au/index.php

With that much output the light needed some serious heat sinking so i scavenged a ropey old bit of aluminium from a local boat builders and took it to Old Man Dave to lathe up. Dave did a great job on what turned out to be a right manky lump of ally and the result was a tight fitting custom heatsink. Cheers Dave

The leds would need a constant current so i ordered the right boost driver from Taskled. TaskLED Home The Hyperboost driver arrived in quick time and I adjusted the trimpot to the maximum 1.2amp output and fitted it into the recess on the back of the heatsink.

I soldered it all together and slipped the 8 3v 3000mah batteries in to the holder, grabbed a magnet and it burst into life.

Everything fit nicely back into the container and a sewed a few magnets into an elastic strap that goes round the body to activate the reed switch.

The theoretical output of the torch is 7x300lumens= 2100lumens. It won't quite be that due to loses from my terrible soldering and the lens inefficiency, but it's bloney bright for sure.

As I mentioned before I'm now working on an umbilical dive light which is based on a mag lite body and runs 3 Seoul P7 leds, which push out up to 900 lumens each. In fact it is all running on the desk already, I've just got to seal it all up and sort out the switching.

I'll post details and pics when it's done if anyone is interested.

 

[Trelawney]

Definatly interested in that project.

 

[foxfish]

Great stuff Tom - looking forward to the night time vids...

 

[Old Man Dave]

Some really nice work especially for a bodger :t . Very impressive Tom. I love projects like this but personally never seem to quite have the time. Good to see such enthusiasm and dedication. Great stuff.

Dave.

 

[Magpie]

I've been asked about cost for doing something like this so thought I'd put a rough breakdown of how much the bits cost:

7 x XP-G R5 led pcb = £30
Optics to suit = £10
Driver = £27
Batteries = £31
Battery holders = £16

Total = £114

So it's not a really a cheap option. On top of that you have the cost of the wire, shrink tube, thermal adhesive, thermal grease and solder if you don't have them already, and of course the cost of a donor torch body.

And there is also the cost of getting a heat sink made if you don't have both a free source of aluminium or copper and a freind with a lathe and the skills to use it.

 

[Jonny250]

Very good Tom, very good.

What would be the limitation on light produced? is it the heat sink limit, or the amount of battery power?
e.g. if there was room, would 10 x those LED's be feasible and would they be brighter?

 

[Magpie]

Both would potentially be limiting factors.

Heat: The good thing for us is the torches are submerged so provided there is a good thermal path from the heat sink to the water we can get away with far more than a non-diving torch can. This is why metal bodied torches are massively more upgradeable than plastic bodied ones are. The plastic bodies insulate the leds from the cooling the water can provide whereas metal bodied torches can conduct a lot of heat into the water.

Battery: Each led needs around 3.5v (varies slightly depending on the type). Taking this torch as an example, it needs 3.5x7=24.5v. My 8 batteries are connected in 2 parallel groups of 4, and each battery supplies about 4v, so that's only 16v. BUT that is where the driver fits in. As well as providing a constant current it also boosts the volatge to that required to provide that current.

But it can only boost it so far. 10 leds would obviously need 35v, which, as it happens, the driver I used could provide, but most couldn't. You can also get BUCK drivers which reduce the voltage but I won't get into that here.

Boosting the voltage that much would also mean the driver would get very hot, and it would also reduce runtime.

A quick calculation shows that running off my batteries the torch will theoretically run for 3 hours. If it had 10 leds that would reduce to 2 hours 10mins.

Would 10 be brighter than 7? Yes, they would, with the constant current driver the luminosity of each led would stay the same. BUT to the human eye it probably wouldn't be all that noticeable. It seems the appearance of brightness is logarithmic. The higher you go, the bigger the increase you need to make an obvious difference. Whilst this produces a theoretical 2100 lumens it would not look 5 times brighter than a 400 lumens torch.

All that said putting 10 of these in would be a bit pointless, if you needed more light you're better off using fewer but higher powered leds, which is exactly what my next one does....

 

[Jonny250]

Cool, so a body board with a hub-cap sized lense cut into the bottom, 10 LEDs from your new torch, and a motorbike battery mounted topside should provide enough 'sunlight' for some shallow flatty bashing without the need for a 'torch' at all

looking forward to hearing how your torch fares in the water...

I just thought, are you going to shoot the fish, or fry them...

 

[foxfish]

Hey Jonny that was my idea! I recon you then just need a telescopic spear & a dry suit so you wont have to even dive or get wet!

 

[Magpie]

rofl You'll need a bit more battery power than that boys. Motorbike batteries seem to be about 3ah 12v, with 10 xp-g's fully driven that'll only last about 40 minutes. Back to the drawing board eh :t

 

[Old Man Dave]

Diesel genny .

Dave.

 

[jtkwest]

IS that thing as bright as those hid lights they have for cave diving? the umbilical kind ? they are really expensive, (3000$us) so at the prices you are talking, yours is far more economical.. it sure looks bright in those pictures. you are obviously some kind of electrical wizard.

 

[Magpie]

In terms of the amount of light out the front, yes, easily as much light, probably more. BUT the light out of a hid will generally be much better focused as it'll use much larger reflectors than I can fit.

So the HID is likely to be brighter in a narrow area, but this would light up a wider area.

In general for dive torches a narrow beam is preferable as it cuts through murk in the water better. Floody torches tend to just light up anything suspended in the water, but they are better for filming as you don't have the bright spot that the camera struggles to cope with.

Far from it, OMD is right, I'm just a bodger! That's the joy of the internet, if you read enough you actually end up learning something. The only difficulty comes in trying to filter out the nonsense!

 

[jtkwest]

cool light

 

[shrek]

what are you hunting that needs so much light? i'm from new zealand and haven't needed to do nite dives to hunt fish but are curious, as i could be missing out on something that looks like fun

 

[Magpie]

Need? Nothing, but when you're out in the pitch dark and the only light source you have is that thing in your hand you always want more, as more light means you see more. It helps you scan the sea bed from the surface and the more powerful the light the deeper it reaches and the bigger area it illuminates.

That, and I got a bit obsessed with it too! Will post details of the umbilical soon.

 

[Old Man Dave]

Night diving is fun, scary at times but fun. It's almost a seperate activity in itself compared to day diving. Catching fish is often the stated intention but sometimes just being in the water at night looking up at the stars and watching the phosphorescence sparkle around you is more than enough in itself.

Most of the fish we target are smallish bottom dwellers that you don't see so much in the daytime. Red mullet and sole are prime candidates but bass and other free swimming fish will also be seen.

There are some great vid's on you tube especially some by our own Magpie. look under Guernsey night dive or similar. I think magpie still posts on you tube as jakethepeg?

Dave.

 

[shrek]

the AA bateries your using are they li ion or ni mh?
i think this looks like a project that has something to it i'm missing out on so i'm going to have a read up and have some fun too

 

[Magpie]

They're not AA's, they're 18650's, which are li-ion, 3v, around 2400mah. They're much wider than aa's and a little longer. They're much happier at the higher drain levels than any aa's are.

Go for it, but be wary that something I got into to try and get a higher powered torch on the cheap ended up spending more than a top spec torch would have cost.

Close Dave, jaketheshed, I haven't put any of the more recent ones on there but this gives you an idea of what there is to see round here on a night dive:

http://www.youtube.com/user/jaketheshed#p/u/11/qigBQ0tTq1c