Torches

[Old Man Dave]

I thought I'd post a thread about torches. Decided on the Beach bar as this may be of interest to spearo's, scubbies and freedivers.

Torches have moved on hugely in the last 4 years and I'll post a bit of a review soon as.

In the mean while I want to look at whether I can upgrade my Princeton Tek Shockwave LED 170 lumens to as good as or better than the new 400 lumens version.

Currently breaking down the torch looks like this. Plastic case with screw on o-ring sealed front cap with bonded in lens. 8 x C cells. 3 x Led's in an "electronics" switching module with on/off and half power. A lens module with 3 lenses (one for each LED. No obvious heat sink.

Over to you Magpie

Dave.

 

[Magpie]

Right then, where to start?

The black cup shaped job that surrounds the leds, is that metal, in which case that's the heat sink, is it plastic, in which case I'm surprised!

If it's plastic the leds will have to be significantly underdriven in order to produce less heat. I suggested before that you could change them for SSC P4 leds but it's possible they already are, just being run at something like 200mah to produce the claimed 170lumens.

Can you do a closeup shot of one of the leds?

8 c-cells, so 9.6-12volts, which leads me to think it's direct drive with the leds in series as each led needs about 3.5ish volts (depends exactly which led), with the current being restricted by resistors to reduce the heat output.

As it's got a half power mode there is clearly some form of regulation going on, the switch probably puts more resistors in the circuit for half power.

So, in summary, the problem you'll get upgrading it is heat. If that black cup is metal you've got some leeway, if it's plastic, you're going to have to either redo the whole internals with a custom heat sink or leave it well alone.

If you can post a closer pic of the led I should be able to tell if its the Luxeon I think it is, in which case a P4 driven at the same current should produce only a little more heat but about twice the lumens and it's the same form factor so the current reflectors should work ok and it'll be a simple case of unsoldering and resoldering.

 

[Trelawney]

Exactly what I did with my 400lm PT Shockwave LED (thanks Magpie!). The cup shaped item is indeed metal. I changed out the Luxeon LEDs to SSC P4s. Can't say i've noticed too much of a difference of brightness. Both the brands of LED look very similar, nigh on identical, next to each other, so i'm not sure if the original ones are Luxeons. But the swap is easy to do.

 

[Old Man Dave]

Interesting Trelawney. I look to you for guidance if I go ahead.

Tom, more info.

The cup is metal and the circuit looks like just some resistors. Trouble is the green printed circuit board is held in place by 2 soldered wires so it's hard to see. However having studied it it looks like the 8 C cells are indeed in series. Some meter work with the torch on showed 9.75 volts from the batteries and 3.05volts at each LED.

So?

Dave.

 

[Trelawney]

God, don't look to me! My father, (an M.o.D Electrical fitter) took the torch apart and resoldered it together again. I just sat there holding things, nodding and agreeing at the appropriate time.rofl

 

[Magpie]

I'd wager the luxeon/P4 swap is exactly what Princetontec did to move the light from 170 to 400 lumens (They did something very similar to move their Apex headlamp from 70 to 130), so you may have just swapped leds for more of the same.

That said, each model of lumens comes in many different "bins" according to their luminosity when tested after production, and the bins generally improve throughout an leds production life so you probably are getting a bit more out of it, but nothing you'd notice, as you've found.

Dave, the 3 volts over the leds shows the effect the resistors are having on the power out of the battery packs, and shows how underdriven the leds are, and that'll solely be for heat management. Thats the problem with plastic bodied led torches, they just insulate the torch not allowing you to take advantage of the cooling of the water as you can on metal bodied dive torches.

Anyway, I'd go for it if I were you. DX do P4's, not the best bin but cheap as, you need to make sure you get the bare led, not one on a star. Like this: DealExtreme: $3.97 SSC Seoul P4 (U-bin) SW0 Bare Emitter

Those are U bin, which are good, but you could get U3 bin for a bit more, and get a bit more light out of them. I've bought bits from this chap before, he's very good.

[ame=http://www.cpfmarketplace.com/mp/showthread.php?p=2443571]●=●=● New: Seoul U3 Binned P4s -- 109 to 118 Lumens -- U3SVNH ●=●=● - CPFMarketPlace[/ame]

You'll need some thermal adhesive to stick the leds down with, and isolate the base of the p4s. DX do cheap stuff which is fine, but Artic Alumina is the best, think that chap on the above link sells that too.

 

[Old Man Dave]

Thanks Tom. As i understand it the resistor mainly controls the amperage which is usually set at 350ma. It's this rather than the voltage that controls output - right? If you change the resistance the led will use more juice and produce more light. Drawback is more heat and shorter runtime. Runtime is no problem I suspect with 8 x C cells but heat might be -yes?

The voltage with original non rechargables would be 8 x 1.5 volts / 3 = nearer 4 volts (say 3.75) after losses). So originally with non recharge the wattage would be 3.75v x 350ma if that's what the resistor was set for. So.... would it be possible to replace the resistor to compensate for the lower voltage of the rechargables and achieve the recommended wattage by upping the amperage. Second would it be worth further changing the resistor to increase the amperage even more so as to increase the light output. What can you run P4's at before they self destruct and what's the output?

Sorry about the amount of brain drain but I seem to be getting there.

Dave.

 

[Magpie]

The amps the led sees will dictate how bright it is and how much heat it puts out. The voltage it needs depends on the amps it is being supplied. It will draw less voltage if it is supplied less amps, or something like that anyway, my understanding gets a bit hazy right there.

No, P4s can take up to 1000mah, 1amp, (this varies depending on the led, some can take over 9 amps now, lumens in their 1000's) before they start struggling at 1amp U bin P4's will be doing about 220ish lumens I think, but they need adequate heat sinking to do so, which they won't get in your plastic bodied torch. That is why they have added resistors to reduce the current, the amps, that the led gets. What level of amps the leds are getting you won't be able to tell unless you break into the circuit and test it.

I'd suggest changing the resistor/s is only going to lead to trouble, they'll have wanted to get the max they can out of the torch so will have tested it and set the resistance level, and hence the current, accordingly.

The P4 is a more efficient led so you can get more light at the same current and same(ish) heat level.

 

[Old Man Dave]

I've ordered three SSC P4 LED's and some silicone heatsink glue. Cost $20 from dealextreme inc delivery.

Been reading up on P4's and seems their base is connected +ve rather than the standard -ve. Apparently this will cause a short if the heat sink baseplate in the torch is connected -ve which is standard. Think this may apply more to metal bodied torches as the body is -ve but with my plastic body may not be a problem. Will check if my ali heatsink base plate in the torch has a connection.

If the ali heatsink plate in the torch is connected -ve then I will need to isolate the P4's +ve LED bases from it. So is the silicone heat transfering glue I've ordered to stick the LED's to the ali heatsink plate an electrical insulator?

Tom?

Dave.

 

[Trelawney]

Thats the glue I used with mine and its fine so far.