I've produced a prototype luminaire which uses high frequency pulse width modulation (PWM) to dim a 40W LED module. The 4kHz PWM frequency means there should be no flicker resulting from using such a lamp for animation if the camera exposure is long enough (something in excess of 1/100 second should be OK).
The use of a stabilised 48v power supply means the light output is not affected by mains voltage variations and using a PWM controlled LED means the colour temperature does not change with brightness.
Heat output is minimal so you can handle the lamp while it is on and it is unlikely to melt your plasticine.
The lamp looks like a miniature stage lamp and can be rigged in a similar fashion or mounted on a tripod.
The prototype is controlled from DragonFrame.
There is still some work to do but details and pictures are on my blog at http://kitinmotion.blogspot.com.au/
This sounds like a good thing! I use inexpensive lights, either small pars from disco lighting shops or home-made from ceiling downlight halogens, but had to spend quite a lot to filter my mains power so I could get a steady voltage.
I think some pro lights with a ballast - like the Dedo lights - are able to operate flicker-free despite varying AC voltage, but they have always been outside my budget.
Good luck with it!
Thanks Nick. I'm going to make a small modification to the lamp circuit board and do another test taking RAW frames.
I'm planning a clay animation so want to avoid excess heat from halogen lamps. We've only just stopped getting temperatures over 40c every day for several weeks here in Exmouth, WA so the studio gets pretty warm anyway, even with the air-con running.
Not that it really matters but I was actually quite impressed with the look of the finished lamp, even if I do say so myself. That dogfood can round the heatsink adds quite a professional appearance I think ;-)
Wow, that is exciting! When I saw 'prototype' I thought you might be working on something that will be going into production, but I see it's more of a basement project thing (love the dogfood can!).
Question - assuming you're successful in making this work properly, is it something the average basement tinkerer will be able to replicate, and will you provide plans or instructions people can follow to build their own?
Also, if someone didn't need it to integrate with Dragonframe, I assume they could do without 'the expensive piece'? In that case would it just require a standard dimmer switch?
Non-tech question - is WA Washington, or more likely Western Australia? (I don't think it's been hot in Washington, so it must be W. Aus.)
I've never been to Washington, Australia it is. We're just into the tropics here on a spit of land called the North West Cape.
I don't actually use 'the expensive piece' but that's the one aspect of the design I won't be discussing in detail. I'm quietly hoping that if this project attracts enough interest, DZED might consider issuing an Arduino sketch to provide data to drive a small number of similar lamps for the many of us for whom a full blown DMX controller is way over the top. The lighting version of their DFMoco sketch.
The lamp itself uses LED units made by Cree and matching mountings/reflectors which screw directly onto the heatsink which has drillings to suit. I got all those bits from Digi-Key. They're a US supplier who also ship to Australia free for orders over $200 AUD. The LEDs are about $25 each, the mountings/reflectors $9 and the heatsinks were mot very much but I can't exactly remember.
There's a simple circuit board with the lamp which you can make at home and the circuit board shown on the blog which is not essential but helps protect your computer against getting a nasty bite up it's USB port if anything goes wrong. Once I'm happy I have a final design working as required, I'll put circuit diagrams and other details on the blog.
The lamps are controlled by an Arduino microcontroller so if you can manage a bit of simple programming (the Arduino and it's programming system are designed for beginners if that includes you) it can take inputs from a wide variety of devices including a simple potentiometer.
If you only want a manual knob to control the light output, that could be done very easily without all the PWM stuff but you would not be able to go below a certain brightness, the lamp would suddenly shut off rather than dim smoothly to nothing. I'm considering putting a similar 'maximum brightness' control on the lamp itself. You would then get the full 255 step dimming from that level down to zero.
Up to you if you don't want the rest of the world to know your question , though if it's about how to connect to DF without a DDMX-2 I won't be discussing that. I have no intention of undermining DZEDs legitimate commercial activity.
As I've stated above, I'd be delighted if DZED take note of the interest in this project and decide to produce a low cost product of their own which is geared towards simple animation studios rather than being able to light a Rolling Stones concert, but that is for them to decide.
Re-reading my last reply, it sounds a bit critical. My apologies for that.
I'm still testing and experimenting at the moment. There are a few changes I need to to make but when I have a final design I'll be putting all the details on my blog.
I agree that DZEDs prices are very reasonable for what they produce, but as purely an amateur I can't justify spending $250 to control 3 or 4 lamps over a table in my shed.
DZED have recognised the low-budget market with their DFMoco sketch for motion control. Over on the Timescapes.org forum (which I highly recommend for anyone interested in building motion control hardware) there are a number of people who use DragonFrame and DFMoco simply to provide motion control for timelapse photography.
I tried to edit the above post but something somewhere locked up.
I was going to add that if DZED had not issued the DFMoco sketch but customers had to spend another $250 to access the motion control data, at least some of the people who bought DF just for motion control for timelapse may not have done so.
Obviously it's up to DZED to make their own commercial decisions but I suspect that a lighting equivalent to the DFMoco sketch would have some sales mileage.
The LED modules are available in a range of colour temperatures.
You'll need to organise your own code for extracting the DMX standard data. There are Arduino sketches around for that already. The conversion to PWM code is public domain already so I'll include that part of my sketch.
The rest of the circuitry and hardware are pretty simple and I'll give details for all of that.