Soup can light, high amps with CC, is it possible?

Waterlights

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Hi all, I've been lurking for a few weeks but need help. I want to replace the fake Cree emitters and non-cc driver on my soup can light. The lights for scuba and its important to have a consistent light output for photography. I'm thinking two XHP50's. I can't find any large soup CC drivers with high amps. Is there anything out there or any way to do this? Thanks!
 

DIWdiver

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What's a soup can light?

Did you know there's a special Dive Lighting subforum? I think it's in the Special Applications Lighting forum. It's not very active any more, and this might not be a good question for it, but just wanted to make sure you knew it was there.

Did you notice in my thumbnail that I'm wearing a drysuit?
 

Waterlights

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What's a soup can light?

Did you know there's a special Dive Lighting subforum? I think it's in the Special Applications Lighting forum. It's not very active any more, and this might not be a good question for it, but just wanted to make sure you knew it was there.

Did you notice in my thumbnail that I'm wearing a drysuit?
Its a term I've seen on the forums for a fat stubby light that uses 4 18650's in parallel (looks like a soup can). My problem has more to do with electronics vs specific dive light problems, but I did try reading the subform without luck.

Also a cold water diver :)...up in Canada the bottom of our lake doesn't get above 42F. Usual temps in summer are 65-72F surface, Sudden thermocline at 30ft to 50F after that it's 42F down to 370ft...but never been down there to test that hypothesis :p
 

DIWdiver

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Can you post a picture of the driver and how it fits in the light?

Note that in order to post a pic you have to have it on another site. Copy a link to the pic, open the "insert image" dialog, and paste the link there.
 

DIWdiver

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That looks like about a 48 or 50mm driver. I'm not aware of anything that large. But that would be the place to start.

How good is the heatsinking for the LEDs? That could be a limiting factor.

Any idea how much room between the battery contact board and the LED board? I'm guessing this is one of those that has a button on the side, and it must be between the two.

Are you planning to build your own LED board? I haven't seen anything like what you want.
 

Waterlights

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That looks like about a 48 or 50mm driver. I'm not aware of anything that large. But that would be the place to start.
Hm.. I didn't think about how the LED's would mount, do I need to make my own pcb? For heat sinking do you think a 50mm copper pcb would cool 30+ watts?

There's about 1.25" between the driver and pcb. Yup, two buttons on the side.

The only driver I found is "46mm - SRK 32x 7135" on mountain electronics. Not 100% sure but I dont think it's constant current. I'm up for the challenge building my own, but thats another can of worms. Do you know any good resources to learn about making drivers? Thanks
 

DIWdiver

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The AMC7135, often abbreviated '7135 or just 7135, is a linear constant current driver. They are often used in multiples. This board has 32 of them, each one putting out 380 mA, for a total of around 12A. It does look like it was made for that style light, so it might be wise to measure your board and see if it is in fact 46 mm diameter. If you wanted a lower top end, you could remove some of the chips and have less total output. Note that many 7135s only put out 350 mA, but higher current versions are available. MTN specifically says these are 380 mA.

If someone is making drivers for these lights, they (or someone else) might be making LED boards as well. It's worth checking into. Making your own copper boards isn't hard, but it isn't cheap. The one low-cost overseas place I found that offered copper would do 5 boards (minimum quantity) in fiberglass for $25. In aluminum they were $82, in copper, $400.

As far as heat dissipation, something around half the electrical power delivered to the LEDs will be converted to light, the other half to heat. So I would base calculations on dissipating 15W, not 30W.

Offhand, I'd guess that the biggest temperature drop would be between the MCPCB and the case, but we'd have to have much more detail about the thermal path from the LEDs to the water before reasonable estimates could be made.
 

Waterlights

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The AMC7135, often abbreviated '7135 or just 7135, is a linear constant current driver. They are often used in multiples.
Wow great, that looks like it may work.

Would it be possible to reuse the mcpcb with genuine Cree led's? If I did solder 10 XM-L2's would the driver still work but cap out at 12 amps? Cree claims max efficiency 175 lm/W vs 105 lm/W at max power. 10 XM-L2's is more expensive than two XHP50's but no need for a new mcpcb and more lumen output. Hm...
 

DIWdiver

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I'd want to measure the input voltage at the LED board to see if it is really 3V. If it is, you could put any combination of LEDs that will fit on the pads. If it's higher than 3V you'll have to map out the board to find out if the LEDs are pairs. You'd need to populate both LEDs of a pair. If the voltage is higher than 6V, you won't be able to use a 7135 based driver.

Does it look like it has XML footprints?
 

Waterlights

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I'd want to measure the input voltage at the LED board to see if it is really 3V.
I meant after replacing the driver with 32x AMC7135, using it to power 10 XM-L2's in parallel. I might even not bother replacing the LED's. I really just want constant brightness.

I found a picture of someone taking apart the same brand light. Oddly, each switch has 4 conductors. The button has a shaft that pushes a momentary switch, no idea why theres 4.

Looks like the driver and LED mcpcb are the same board? There's another 4 wires going to the battery contact board (2 red, 2 black), also not sure why.

 
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DIWdiver

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Yes, it's not surprising to find the driver and LEDs on the same MCPCB. No idea why there are 4 wires on each switch. Does it react differently to slight and full depression? I would guess that the multiple wires to the battery board suggest the batteries are not all simply in parallel.
 

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