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UltravioletPhotography

Caps, Caps, Caps


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Last autumn I presented an idea of supplying the Nemo torch from an external DC-source instead of a battery.

https://www.ultravio...dpost__p__39017

 

The general idea was to generate the optimally low voltage for maximum output power with minimal heat losses.

Later I decided to make this as a proper design effort instead of building a rats-nest.

 

It was more complicated and expensive than I first expected, but a few months ago I had something working well.

 

There were many iterations of the Cap-shell:

post-150-0-80140500-1616666078.jpg

 

I also had to buy a special thread-cutting tap matching the one on the Nemo's lamp-head and create a few assembly fixtures to make it possible to put all parts together properly.

I designed a custom PCB and had to add an internal heatsink to keep the dcdc-converter from overheating.

I have run them a few hours without any problem, except that they get hot to touch.

The normal battery used with Nemo can not keep up the voltage above 3.8V for full optical power many tens of minutes.

 

Here are some images showing the parts:

post-150-0-56587000-1616666358.jpg

post-150-0-74447300-1616666385.jpg

post-150-0-23843600-1616666333.jpg

 

These caps run on a dc voltage between 7V and 22V, with an optimum efficiency around 12V.

The other voltages work well too.

 

The lower voltage makes it possible to run the caps, off grid, with Bike light battery-magazines like these

https://www.ebay.com...ED/162709619747

https://www.ebay.com...ht/124044447618

 

They can also run on any acdc adapter with suitable connector similar these 12V 2A versions:

https://www.ebay.com...p/233918373015?

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Nice Ulf. Having the torch head run on a bench power supply would be a good idea. If you have a long cable you can raise the voltage to have less current and less losses.
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Well I started designing them just for the fun of the process.

That is my drive in life, to create well working things.

 

When I was to far into the project there were no reason to stop even if they turned out to be more expensive in parts and needed tools than I could imagine in the beginning.

They are far too time consuming to build to continue to make them in any big numbers.

 

This was not a pitch to sell against the rules here.

As handcrafted items with components bought in rather small numbers I think they would be a bit too expensive to sell anyway, even if I charged zero for my work making them.

 

I have most of the essential components to build a few more, but might be too busy with work soon to do that reasonably quick.

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I purchased a pair from Ulf and they are great. I have a small 25mm arca swiss plate screwed on the bottom to mount on tripods with tilt heads.

One of the Nemo looks to be quite dimm though, not due to the caps, as I flipped it out with one of my other Nemo heads.

 

So there is some Nemo variation.

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I purchased a pair from Ulf and they are great. I have a small 25mm arca swiss plate screwed on the bottom to mount on tripods with tilt heads.

One of the Nemo looks to be quite dimm though, not due to the caps, as I flipped it out with one of my other Nemo heads.

 

So there is some Nemo variation.

 

Glad you liked them.

 

David was my motivator to go all the way with the project.

 

There can be several reasons for a dim LED

  1. A lemon LED
  2. Aging due to overheating due to bad cooling of the LED insufficient due to lack of thermal paste behind the LED's metal board thermally connecting it against the head-metal
  3. Aging due to overheating due to bad cooling of the LED's metal board if it was not pushed sufficiently against the head-metal by the reflector.
  4. Too low voltage from the cap if the adjustment to 3.8V changed. I made the adjustment carefully and then after one hours burn-in verified that it still was OK. (not a problem here for David as he has verified with another Nemo-head)

These 10W ("15W") LEDs needs much cooling to keep the shining LED-chip within a working temperature for a good life span.

The cooling is done by the metal in the lamp-head that should be well coupled to the LEDs metal pcb with thermally conducting paste.

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Odd just tested it and same brightness as my other 3. I think it just needed to be hit.

So must be a loose something. If it acts up again I might just take it apart and see if a driver came unset due to shipping.

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Was just a joke. I remembered a Top Gear episode quickly in my brain when Stefano said lemon, where the hosts had x dollars to buy some crazy British beaters.

Some of the parts didn't always stay on.

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