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Making a Multi Colour High Power LED Illuminator

Acancarter

I'm retired and living in Northamptonshire, so plenty of time for photography.
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Making a Multi Colour High Power LED Illuminator

5 Apr 2021 12:47PM   Views : 338 Unique : 208

Making an LED Multicolour Flash/ Illuminator/ Strobe

For those of you who have looked at my images or read any of my blog posts you will know I like to try some quirky optical things with a bit of electronics thrown in for my photography. I have posted a few images taken with a high power LED illuminator I have been working on, including one today.

LEDs have become remarkably good, efficient and cheap. The technology inside them is remarkable, involving layer stacks of ‘quaternary or quinternary’ semiconductor materials (AlGaInPN) just a few atoms thick… Nobel Prize winning, world changing technology, absolutely amazing.

I wanted to try and make a versatile illuminator, mainly for fun, but also because I had a few photographic ideas to try out. The whole thing needs some polishing - particularly the user interface and software - but is now at the trial state so I can see how much more work is worth putting into it!

The light sources are 30 and 50W R, G, B, White LED blocks, primarily designed for things like traffic lights or floodlights. Look on ebay and you will find them at a few pounds each. Note that these come in two types - one with the power conditioning circuits included (which isn’t suitable) and ones with the raw connections to the LEDs, which are suitable. These need something like 1A at 35V (30W) or 3A at 35V (100W, but only seem to be white). At these power levels these lamps are SCARY bright! They also need to be well heat sunk, or they will fail quickly!

Below is a photo of 8 of these assembled on an Aluminium plate. These will run continuously at full power, but that would need a 35V 14A power supply… quite a beast! I didn’t want to run them like this - just at say 10% for modelling, then at maybe up to 200% in a short flash, or sequence of flashes. to enable control of the lights and the sequence there are 4 power transistors on the same heatsink.
331023_1617622610.jpg

It shouldn't do the LEDs any harm to overrate them for short pulses as they won’t heat up much. How much is an unknown. I'm aiming to test some to destruction at some point (Elon Musk approach?). Generating the current pulses is more of a problem!

This is the back view. It is a birds nest of stuff, I know. This is pretty much a trial/ prototype, so has had a lot of adjustments and replacements as I’ve gone along.
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The circuit (for the techie amongst us) is four channels of programmable gated current sources, so they can be pulsed for any duration to any current within the range of the supply. The voltage is supplied through a ‘boost’ converter (shown on the first pic) - again a very cheap bit of electronics you can buy on line. This takes 12V in (from a drill battery) and converts it to 48V, with around 2A max current (it switches off if you take too much). To give the power for sequences of pulses there are a couple of large capacitors, just as there will be to store the flash energy in a speed light.

Front View. Looks a bit more conventional..
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The sequencing and intensity of each flash is controlled from a Raspberry Pi, although I will be using an Arduino for the portable version. These are very easy to set up and programme. Plenty on the web, and now widely taught in schools.

So what does it do? It can produce any sequence of colours (not just RGBW - you can mix them for all intermediate colours) and in any duration. 1/500s will freeze most motion, 1/50s will give good blur. The LEDs pulse very happily at 1/10000s, but you don’t get much light from them. A sppedlight might put out about 50W seconds - very bright, short pulse. For 1/100second, this illuminator will put out about 3-500W, so only 3-5W seconds, so don’t expect speed light or strobe brightness, but it looks like it will be good enough for people shots, including running and dancing.

I started with some close images, such as the ‘Colour of Pearls’ and ‘Precious Things’ below. These didn’t need too much power, but show what can be done with different colour sequencing.
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]

To make the illuminator more suitable for people, I had to slave it to the camera. A continuous colour changing bright flashing light isn’t pleasant. Like a disco strobe. Maybe dangerous. So I added a light sensor that triggers the illuminator from a camera flash (suitably masked so it doesn’t contribute to the exposure).

First trial (yesterday!) is the Crazy Man selphi just posted. This was with 1/500s pulses, ISO 500, around 1.5m from the illuminator. next target is to make it portable and get it outside at night to scare the wildlife (and the neighbours!)
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I’ll keep you posted on progress. If you are interested in more detail, schematics, code etc just message me!

Comments


dudler Plus
17 1.6k 1835 England
5 Apr 2021 3:40PM
I'm not sure how many people will make one if these, Andy - but it's quite a good thing to know that it's possible, and there may well be a few who either find out how to do it, or find a friend who can, because they want to exploit the creative possibilities.

Is it possible to vary the pulse rate (as opposed to length)? That might open up further possibilities for the techno-creatives among us... That could be used to alter the separation of successive images where it's not feasible (or not easy) to alter the speed at which something moves.
Hi John, thanks for the comments. it would be amazing if anyone else built one of these! I'd be so pleased. As you might expect, absolutely everything is adjustable, pulse width, pulse to pulse delay, pulse colour, pulse intensity. You can even change the intensity or colour profile within a pulse (can't do that with a speed light or a $$$$strobe). I thought progressive pulse contraction might enhance movement, starting with long pulses to give blur then progressing to finish with a bright short white pulse to give sharpness. I have in my mind an interpretation of 'Chariots of Fire'. The bright psychedelic colours need toning down for more serious work. It needs ideas and exploration - it only takes a few minutes to programme in the sequences. As it isn't that bright, it needs to be operated in a dim environment, or outside in the evening. Otherwise the daylight will smear and reduce the effects. I'm intending to add a 'modelling' light setting for composition and AF, which then dims for the sequence exposure. Maybe you will be up for some fun post lockdown! all the best Andy
dudler Plus
17 1.6k 1835 England
5 Apr 2021 5:46PM
I reckon that a completely dark studio would be an ideal place to play with this - preferably, a studio with black walls...
Absolutely agree. Anything in mind? I’ll work on the user interface to make reprogramming quick. I can probably do this more easily with a laptop rather than trying to embed the flexibility in the microcontroller. See if I can boost power by a couple of stops. The white isn’t difficult, it is more the blue and red. Would a second slave or independent unit increase artistic and lighting possibilities? Any spec suggestions for a beta model?
dudler Plus
17 1.6k 1835 England
5 Apr 2021 9:14PM
A second unit would probably open up vastly more possibilities - but I'm not the right person to exploit them...

Actually, I know very few studios that approach a full blackout: I shall look for one! And black studios are incredibly rare - the only one that I can think of offhand is only secondarily a studio - most of the time it's a dungeon!
FredColon 1 1 United Kingdom
6 Apr 2021 8:47AM
Interesting article - thanks for posting.

I've been tinkering for a while with both a Raspberry Pi and an Arduino and was looking at this https://coolcomponents.co.uk/collections/leds/products/neopixel-ring-24-x-ws2812-5050-rgb-led-with-integrated-drivers

I was considering it as something I may get and play with. It's nowhere near as bright as your construction and I doubt it would work well as a flash, but I've fancied a ring light [and this item would go round my lenses] to help illuminate close-up / macro photos -- this may be clunkier than a purpose built one but would allow some interesting colour effects.
Hi Fred - thanks for reading this and for your comments! I'd very much encourage you to have a go and see what the results are! The ring looks a bit small to go round most lenses though - an alternative is to buy RGBW light strips and adapt them (quite a bit cheaper) but you won't get the pixel by pixel colour options. I used LEDs cut from these strips for the harmonograph images I've posted here and on smug mug. I've always found the adafruit parts to be very good, and well supported for software! Good luck, Andy
FredColon 1 1 United Kingdom
9 Apr 2021 2:19PM
Hi,

Thanks for providing the 'kick' to get me started Smile

A few days later, I got the LED ring (plus some other bits & pieces) and have tried a set-up.

I'll post a picture later but at the moment I have a rather "Heath Robinson" set up with Arduino, Power supply, breadboard all loosely tied to my tripod and the ring around my lens. It was advertised as having an inner diameter of 52.5mm -- great for fixing to a 52mm filter, I thought. Didn't quite work out -- long story short, my temporary fix is using the lid of a coffee can with the centre section cut out as a support.

As and when I tidy it up [and possibly beg/pay a friend to make a 3D printed custom mount], I'll add extra picture updates.
FredColon 1 1 United Kingdom
9 Apr 2021 3:35PM
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Here's the first iteration (please excuse untidy room Blush ).

I'm working on making a more stable support. I'll probably continue to use the Mac laptop to program the Arduino (colours, intensities...) as I can also use it to drive the camera using WiFi tethering.

This is never going to be portable - or robust enough for serious studio work. It did / does provide me with amusement and an interesting project at a low cost. Will experiment with different colours now (24 LEDs at 16.7 million colours each should provide plenty of scope for playingWink )
Fred - thats splendid! Macs with Arduinos are very hit and miss it seems. My old mac pro just will not recognise an Arduino, despite trying every trick and driver in the book or tip on the internet. I have to use the IDE on a RPi to programme it...or snaffle my wife's MacBook... the ring will be great for macro work - I'll look forward to seeing some results!

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