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Converting 12V halogen film lights to LED Answered

I have had these 3, 12V dimmer transformer film/photography "Dedolights" since I worked at the BBC (UK) many years ago working on filming projects and they have been constant and loyal friends.

The transformers have packed up now but the lamp housing and optics remains as solid as ever.

My aim is to attempt to DIY convert the light sources to LED and a colour temperature of approx 6000K, so I can mix them with my other daylight lighting.

If you look at the pictures in the attached pdf file you will see this is no easy task !

So ideally I am looking for a high output LED bulb to replace the halogens as a straight swop or, as is more likely, change the fitting altogether to get a high power 12V light source.

Help and suggestions would be most welcome.


I am attaching a pdf file to give more info and pictures

Thanks in advance

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evamajlak
evamajlak

12 months ago

Thank you really for sharing this piece of information. I guess your experience of working at BBC has paid off really.

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Downunder35m
Downunder35m

12 months ago

The real problem is not the light but the dimensions of the bulb.
For the lens you need a certain filament lenght and disatance.
Have a look at LED replacements for car fog lights, H3, H1 lights...
Some might fit the filament lenght close enough.
If you need something to fit the reflector then look for high power LED chip or cob lights.
These however require a dedicated drive while the car solution comes ready to go for 12V.

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Jack A Lopez
Jack A Lopez

12 months ago

Regarding, "constant and loyal friends" I am hoping that phrase refers to your Dedolights, rather than the BBC news organ, because I really do not trust those guys.

First of all, was that time when they lied about where spaghetti comes from.

https://en.wikipedia.org/wiki/Spaghetti-tree_hoax

I know that one was intended as a joke, but there was also that one other time they aired a report about an unexpected building collapse, before it actually happened.

https://www.quora.com/Why-did-the-BBC-report-the-WTC-Building-7-collapse-twenty-minutes-in-advance-of-the-event?share=1

That seemed rather shady to me as well.

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Jack A Lopez
Jack A Lopez

12 months ago

Well, I think Step 1 is to contemplate what quantity of light, in lumens, is approximately a replacement for the previous halogen, incandescent bulb.

To do that I look at table I found, in the Wikipedia article for, "Luminous efficacy"

https://en.wikipedia.org/wiki/Luminous_efficacy#Ex...

that compares a bunch of different lighting technologies.

And from looking at that table, I am going to guess the amount of power wanted by an LED module will be smaller by a factor of about 3 or 4.

I noticed, in your PDF, a picture of a paperboard box, with the scribbles, "12V 100W."

So that suggests, about 25 watt to 33 watt of LED module. I am expecting it will want a heat sink, especially if it is small enough to fit in the space where the halogen bulb and reflector behind it, are now.

Also I am expecting this LED module will require a constant current type driver.

In searching the web to find a tutorial that explains how to put these things together, I found Julian Ilett's Youtube channel.

In my opinion, this guy knows what he is doing, and I am going to point you towards one of his videos on this topic.

The LED module in this example, is only being driven at 10 watts. (I know I estimated your light would want about 25 to 33 watts.) But I think this video is a good introduction to the topic, and shows the essential elements, an LED module, a heatsink, and a constant current driver that is a good match to the LED module.



By the way, adjustable current, constant current drivers exist, and essentially that is a way to adjust the brightness of the LED module by turning a knob. I thought I would mention that since you mentioned your previous lights were dimmable.

Also the last time someone asked this question here, about two months ago, I think the answer I wrote was more vague, but maybe that was because I could not quite picture the set up that person was describing, but it was also a portable halogen, incandescent light.

https://www.instructables.com/community/LED-TORCH-...

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carpinteros
carpinteros

12 months ago

Thanks for share! very nice work