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UltravioletPhotography

To specify an ideal strong UV-flashlight?


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I like to play with technical design ideas.

Lately I have pondered some about how a really good strong UV-flashlight should look like.

Now I would welcome the input from other members with more experience using them as light sources for photography.

 

With some luck we might specify something really useful that could be built.

(I will add to and expand this first post when I get inputs to keep the information in one place)

 

I already have a few Convoy UV-flashlights with filters that I use for focussing in UV and looking for fluorescence, but never for fluorescence-photography.

A few years ago I also built a UV-LED based lamp with a 50W 365nm LED array that is strong and nice.

The design of that lamp is not that well balanced, making it less than optimal. https://www.ultravio...dpost__p__30470

I think it will work well enough for me, but it would be interesting to design something more optimal with more modern components.

 

First a list of "must have" that I think should be included (or not?):

  1. Peak at 365-370nm. (Are possible alternatives needed?)
  2. Possible to attach suitable filters. Dimensions TBD
  3. Even light pattern without hotspots
  4. Strong light, definitely more than a Convoy S2+. TBD
  5. If with cooling fan, not blowing air forward, to avoid disturbing sensitive motifs.
  6. Enough cooling to keep the LEDs temperature low enough, both for efficiency and lifespan. TBD
  7. Use some standard battery type. LiPo? 18650 or bigger?
  8. Weight low enough to be nice to carry and handle. TBD
  9. Over-temperature protection for the LEDs
  10. Wide input power range. TBD

A question:

Strong light give shorter exposure time and activation of weaker fluorescence.

-- Must the lamp be able to run at full power for a long time or only for shorter periods.

-- How long must it be able to run if the time should be limited.

 

Secondly a list of possible "nice to have"features:

  1. A 1/4" thread for tripod mounting
  2. A handle or shape for comfortable hand-holding
  3. Easily exchangeable batteries
  4. Possible to be run with a mains power adapter. (24V?)
  5. Possible to charge the batteries with a mains power adapter. (same?)
  6. Variable on-timer.
  7. Low battery warning indicator
  8. Separate lamp and battery/power unit connected with a cable.

Please give comments to these lists and suggest other features that could be important or usable.

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Good thread Ulf, I too am looking at building some UV LED lighting.

I am expecting one of the same LEDs that you have used in this posy...https://www.ultravioletphotography.com/content/index.php/topic/3510-paint-torch-reflector-black/page__view__findpost__p__30470

I would like to know how you powered it please ?

Cheers

Col

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Hi Col,

 

It was some years ago and I cannot find the exact model.

However it was something like this:https://www.ebay.com...bIAAOSwEVlb8AMu

The one above was not correct. It was without CC.

This is more like the one I used: https://www.ebay.com...PQAAOSwWylcwXnD

 

This might be a better alternative, but I have not tested it:

https://www.ebay.com...1QAAOSwhctdajCq

I think it could be a candidate for the design project in this thread.

 

 

The input voltage must be lower than the output voltage and it is still good to have it reasonably high to keep the input current low and keep the conversion efficiency up.

Be aware of that the input and output grounds are not at the same voltage.

 

I have mostly been running mine with a 24V mains adapter.

 

My LED module is mounted on a big heat sink with a fan.

The Fan is running on a small adjustable DC-DC step down adapter.

 

Today I would have used a CPU-cooler or similar instead.

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I have just found that the 7W 365nm LED light bulb is easy to remove the clear top dome & place a 52mm U340 filter in a ring, into the surrounding bulb.

https://www.amazon.c...0845566&sr=8-25

51RhjDtQR1L._AC_SL1000_.jpg

The clear dome is adhered with silicone & by running a box cutter blade around the join with the body, the dome is easily detached & a 52mm filter ring inserted, eg U340.

post-31-0-50753600-1570847623.jpg

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Yes,

Now your bulb looks like mine. Although I used a 55mm to 52mm step down ring on the bulb.

I use 2 of these in desk lamps for most of my images.

My recent Canon 40mm f2.8 pancake lens test was done with 2 of these.

 

But since we have been talking about this bulb the price has shot up. I see they are now $29 each. I got mine at $19 each.

 

This what mine looks like:

https://www.ultravioletphotography.com/content/index.php/topic/3124-diffuse-uva-led-lighting/page__hl__bulb__fromsearch__1

 

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  • 3 weeks later...

I do not remember. Sorry.

Hope this can be of some help:

 

I experimented first to get a feeling of the function of the trim-pots. They are fixed now.

 

Do like this:

Check the output voltage when turning the CV-pot. Do this without the LEDs

You might need a small load with a resistor drawing a few mA.

 

F.Y.I the output will never go far below the input voltage for this type of converter, as it is an UP-converter.

Also The LED array will not turn on or conduct much before the voltage reach above around 28-30V.

The LED-array must be connected the right way, + to +voltage.

 

The CV-pot's function will only be as expected when the pot's setting is higher than the input voltage.

You might have to turn the pot several times without any reaction, before you reach that position.

If you turn down the endpoints for the pot is not possible to feel when turning, but if you reach it there is a faint click once per revolution.

If you hear the clicking change the turning direction.

 

If you have a variable power supply you might start feeding the converter with 10-12V, as that gives you more turns on the pot that change the output voltage.

Starting with 24V in is also OK, but you'll get more dead turns, before anything happens

 

When you know the turning direction, set the output voltage to something like 25-27V.

Switch off or disconnect the power source and connect the LED array or a suitable power resistor.

A 18Ω resistor that can handle ≥50W is an alternative load if you want to experiment before you get the LED.

 

Turn the array away from you against something that have fluorescence like a paper to monitor the UV-output safely.

 

If you can, measure the current with a multimeter. Connect it in series with the LEDs.

Decide what current you want to feed to the array and adjust both pots until you reach it.

 

Ideally the CC-pot should be the one setting the current and intensity.

The CV-pot should then be set for a voltage slightly higher with no load.

This can be done, while monitoring the current, by successively increasing both CV and CC, but finishing with CC and then turning the CV slightly higher, without getting any current change.

 

I hope that these instructions are possible to understand. If anything is unclear I'll try to clarify.

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