[SML] Stars and fireflies from behind a cyc

[Jerry Durand]

For LEDs, wire as: 

Battery Positive->switch->capacitor->resistor->LED

Capacitor and LED negative go to battery ground.

Eons ago I made a bright incandescent pot that faded to full on picking
up and faded to off on setting down.  The circuit was only slightly more
complicated having a power transistor to control the light level, the
lamp was an automotive tail light.  As the pot was supposed to be heavy
I just used a small lead-acid gel cell for power.  There was a switch
hidden in the handle one actor could bring it out and set it down
without it glowing and then arm it so it would glow when the other actor
picked it up.

Only problem was the props person kept forgetting when it was to be used
and would take it off the ready table and return to storage so the actor
had to look around for it.  Remedy is shoot the props person.

On 06/15/2016 11:09 PM, Joe D via Stagecraft wrote:
> I am involved with a production of "Honk Jr", and am working on the scene where the Ugly Duckling visits the frogs.  We are considering making use of our sky-blue cyc, and doing a few things from behind.
>
> We would prefer evening, but I realize that making the sky-blue cyc look black is not going to work because of ambient light. So, my target will be early twilight. There would be a few stars showing, the moon, and fireflies.
>
> My hope is that the cyc will be translucent enough for my point light sources to be seen through it. 
> I believe it is Rose Brand’s Poly Cyc 
> Width of fabric 120 inches           
> Fiber content: 100% polyester           
> Grams per square meter: 1200 (38.71 oz per linear yard)  
>
> The moon is a simple light box.
>
> Stars might be made by using standard Christmas twinkle lights (fairy lights for those across the pond). I would hang them behind the cyc, with at least half of the lights taped over, so they are more dispersed.  A possible alternative, that will allow for a brighter light source, is to connect perhaps 5 to 10 white LEDs
>
> Then, for the fireflies, I picture making use of perhaps 8 kids.  I would make each of them a pair of fireflies.  The fireflies would be made by getting some cheap $1 store penlights.  Then, attaching a 24" rod, and putting green incandescent lamps at the end. They would be instructed to turn the LED on and off as they flew around.  The fireflies might also dance along with a song that is in that scene. I might do this circuit, though my electronics training is a few decades old, and rarely used.  Here is the circuit I have in mind;
>   |----/\/\/\----|-------------|
>   |             _|_            |
> 3V dc           ___CAP        ( )Incandescent 
>   |              |             | Lamp
>   |--------------|-------------|
>
> The idea is the battery charges the capacitor through the resistor, and as the capacitor charges, the lamps gradually gets brighter. Then, when the power is cut off, the lamps fade out.  Actually, LEDs are probably better in some ways, but I recall that they don't dim nicely by just varying the voltage.
>
> I have a few concerns.  My light sources from behind will probably tend to provide some general illumination on the cyc in their vicinity.  I am less concerned about the moon and stars, since they can be touching the fabric.  
>
> But, the fireflies are a different matter. To keep the kids from constantly bumping against the cyc, I will probably need to keep the fireflies at least a foot or two away from the fabric.  Green laser pointers might would do a nice point light source, but it may be too bright.  Plus I could not make them fade in and out with a simple circuit.
>
> I am sure some experimentation is in order. But, writing this note to you all both helps me to organize the design, and perhaps save me the trouble of testing a bad idea that someone else has tried.
>
> Thoughts on this idea?
>
> -Joe
>
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-- 
Jerry Durand, Durand Interstellar, Inc.  http://interstellar.com
tel: +1 408 356-3886, USA toll free: 1 866 356-3886

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