Thursday, 12 September 2013

Never one to do things the easy way, I want to use lighting controlled by DragonFrame to add to the overall look of this piece. Paying serious money for large, hot, tungsten based stage lighting is not an option, either from the financial or where-on-Earth-are-we-going-to-store-these(?) points of view. Available LED lights are also large and expensive as well as likely to induce serious flicker when faded.

So, I've designed a reasonably high brightness, high frequency PWM (Pulse Width Modulation), small, inexpensive LED lighting system specifically intended for use on table-top animation sets. Power demand is low, heat output is minimal, flicker when dimmed is eliminated, overhead rigging for mounting the lights can be lightweight and easy to pack away. You can even change reflectors to alter the angle of the beam!

Here's the prototype lamp itself:

The power supply is a 48v switch-mode unit. A small circuit board on the far end of the heatsink provides a constant-current source for the LED (the correct way to maintain a steady light output) and can turn the lamp on and off at high frequency under PWM control from an Arduino controller.
The final design may require a fan on the heatsink and will have suitable hanging brackets mounted onto the slotted cooling fins you can see in the picture. Unfortunately control from DragonFrame will require the purchase of a DMX-2 interface box (the single most expensive component in the whole rig) and DMX decoding software on the Arduino controller.
I'm currently waiting for some high speed opto-isolators to arrive from RS so that I can see whether the lamp will fade properly at a PWM frequency of more than 10kHz. I recon this speed should avoid any flicker at any of the exposure settings expected in the real world. We shall see!

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