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  #11  
Old 17th February 2016, 07:21 PM
cesare cesare is offline
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I've been talking about making an LED light source for my Durst enlargers for a while, and got as far as knocking up a trial earlier in the year.

Basically, i'm using high power 10w LEDs, both blue and green, mounted onto an aluminium heatsink. The LEDs are driven by constant current converters, which have a duty cycle input, so basically I can drive the converters from a microcontroller, which is then acting as a timer, and by driving either the green or blue LEDs, and at varying duty cycles, I can achieve different grades.

My mockup of the setup exposed paper through a graded step, and this gave me more than enough light from 20w of LEDs compared to the 250w of halogen, much more at the blue end.

I'm working on the microcontroller logic, planning on using an arduino with a simple LED display, and rotary encoders to set the grade and the exposure time.

I'm in the process of getting some white LEDs to act as a focus light, and with another constant current driver i'll be in a position to design a head, and to go from there.

Once i'm done, i'll probably be able to offer a basic design and code to produce an equivalent control panel and head if anyone else would be interested. Total cost is around £100 i'd guess, but it'll depend on casework for the controller, and what sort of stuff you need at the head end to work for you. I'm using an existing durst 5*4 mixing box (two diffusers with a reflective conduit between them) and get very even lighting, but i'd have thought a much simpler arrangement could be designed.

It's fun to combine my interest in photography and printing, with the day job (programming).
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  #12  
Old 17th February 2016, 07:31 PM
SanMiguel SanMiguel is offline
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cesare well done my friend. That has been on my to-do list for a while now but I haven't got beyond experimenting with various off-the-shelf white LEDs and under-the-lens filters.

I would certainly be interested in your design. While I've never worked with microcontrollers I'm competent in C/C++ so hopefully should be able to follow your design OK.

Michael
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  #13  
Old 17th February 2016, 09:45 PM
cesare cesare is offline
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Well if you are happy with C/C++, then i'd suggest you grab the arduino development environment, install it, and have a look at the sample applications they include - you'll get a feel for how simple it is to write simple programs for this microcontroller.

With a controller plugged in, you compile your code, then 'run' it, which downloads it via USB to the board, and starts the logic. It's flashed onto the board, so if you disconnect it from your computer, then connect a 9v battery, it'll spring to life running your code. It's very simple, and very flexible.

I have a development board with a breadboard, so i'm still prototyping controls and a design, and working on debouncing inputs, and getting a set of controls for the simple screen i've got which will work for me.
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  #14  
Old 21st February 2016, 10:24 AM
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vanannan vanannan is offline
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OK, I have made my warm light LED array using strips of LED tape, 126 leds total, not installed in enlarger head yet but looking good, slight problem is that there is a slight over run of about 1.5 seconds fading which presents a problem when using a timer between mains and transformer, attached is a link showing the transformer I am using, is there an alternative transformer that will not run on after cutting the power?

http://www.ebay.co.uk/itm/3516444862...%3AMEBIDX%3AIT

Many thanks for all your info and suggestions
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  #15  
Old 21st February 2016, 05:02 PM
JOReynolds JOReynolds is offline
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Quote:
Originally Posted by vanannan View Post
is there an alternative transformer that will not run on after cutting the power?
You will need to leave the transformer connected to the mains and interrupt the current flowing through the LEDs. If the timer can't be opened to access the output relay contacts, you will need another relay, its coil powered by the timer output, its contacts making or breaking the LED current. Since the relay will be connected to mains electricity it must be in an insulated box. Don't tackle this project unless you are familiar with the hazards.
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  #16  
Old 21st February 2016, 05:36 PM
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vanannan vanannan is offline
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Quote:
Originally Posted by JOReynolds View Post
You will need to leave the transformer connected to the mains and interrupt the current flowing through the LEDs. If the timer can't be opened to access the output relay contacts, you will need another relay, its coil powered by the timer output, its contacts making or breaking the LED current. Since the relay will be connected to mains electricity it must be in an insulated box. Don't tackle this project unless you are familiar with the hazards.
Thanks Jo
I will try and seek out a cheap relay, this project is just for fun so I don't want to spend too much, I am up to about £20 so far for LEDs, transformer and a length of wire for connecting the led strips together, I am quite competent at soldering now
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  #17  
Old 1st March 2016, 09:02 PM
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GoodOldNorm GoodOldNorm is offline
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http://www.largeformatphotography.in...5x7-E6-LED-Mod
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  #18  
Old 24th August 2022, 07:31 AM
Pop Alexandra Pop Alexandra is offline
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Quote:
Originally Posted by GoodOldNorm View Post
You can also find similar lights at NDR Electric, in case you're still interested.
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