Just for Fun! Smallest Scale Model Animation?
My recent NNGC clinics, and one at our local 2nd Division NMRA PNR clinic generated an unusual amount of interest. Since I had put in a fairly significant amount of preparation, it was really satisfying. But I was overwhelmed by the interest in what amounted to be a relatively simple, but incredibly tiny (but accurate) animation, I had added at the end of my efforts.
You can have a look at it here:
Friend of the Crew
Making a “Critter”
The “Critter” is simulated with a tiny (and I mean tiny) drop of Testors’ Pactra Fluorescent Yellow Paint, usually found in the RC Racing Car side of your local hobby shop. Note: this is NOT day-glow paint, which does not glow nearly as bright, but stays glowing longer. The Testors’ Fluorescent Paint glows quite bright under UltraViolet (UV) light.
Mix the paint thoroughly, and take a tiny bit of it on the end of a pin or toothpick, and apply it to the underside tip of a bush or shrub on your layout. Next get a 5mm UV LED (almost any will do, I chose one from Surplus Gizmos (http://www.surplusgizmos.com/5mm-UV-LED-4000-uW-25mA-Ultraviolet_p_1457.html)
Then drill a 1/16inch hole in the top of it about 1/3 of the way down into the plastic housing from the top center, an place a length of 1/16 brass tube into the hole you just drilled, glue with ACC, and let dry. Then paint the entire LED and tube (but not the opening!) with a couple of coats of black paint and let dry. Now from the underside of where your firefly will be “glowing,” drill a hole at an angle towards the firefly and away from the viewer. Insert the LED/tube assembly from the bottom until the tube appears above “ground.” If necessary, hide the tube with some grass or bush.
Construction Diagram
Now the only thing you need to know is the correct timing for a North American Yellow-Green Single Blinking Firefly Photinus collustrans at 76 degrees Fahrenheit—which is about a 3 second repetition rate with about a 0.4 second duration, with some random variation. The timing is done with precision and pseudo random variation by an Arduino Pro Mini:
In the Setup () section, insert:
fly_time = millis()+1000; // This sets the first “glow time” at 1 second ahead from NOW
And in the Loop() section place:
if (millis()> =fly_time) { // Have we hit the next time to “glow”??
digitalWrite(fly,LOW); // This actually turns the Firefly “on”
delay(random(180,570)); // This lites the fly for 180-570 milliseconds
fly_time=millis()+random(2900,3500); // This sets the time ahead for the next “glow”
digitalWrite(fly,HIGH); // This turns the Flirefly off
}
I should also point out that the exact same technique can be used to light up turn signals and small maker lights on auto and trucks, with a coating over the appropriate “light!”
That’s all there is to it! To watch grown adults enthusiastically scamper over to see this in person, beyond all else is amazing! I don’t really know if this is the smallest, scale model animation in the world, but it probably vies for the title! (smaller, even than a scale model lit cigarette!) (Background sounds by Fantasonics!)
You can get downloadable references to my last NMRA clinics here:
http://home.comcast.net/~gbglacier/
I hope you enjoy them too! As always, appropriate suggestions and comments are welcome!
Have fun! 
Best Regards,
Geoff Bunza
