I have assembled several of my LED Fader circuits, and since I had so many orange and yellow LEDs, I decided to use those instead of the original red LEDs (each board takes 6 LEDs). The circuit uses one transistor and three RC sections to make a PSO (phase shift oscillator), and another transistor to drive the LEDs. I have been experimenting with the values of the resistors and capacitors in the three RC sections that make up the phase shift part of the circuit. I started out with 47uF and 33k for each RC section, and I changed the Rs to 39k for a bit slower frequency. Then the last one I assembled I used 4.7uF and 47k, but it was too fast and frantic so I changed to 82k, and the frequency was 1.6 Hz, which is more tolerable.
I decided that I should put some of these circuit to good use, so I thought about what I should do with hem. I´ve seen stage prop type of fires with fake flames. I believe they use a thin flap of translucent plastic above a small fan to give it motion, then some amber or yellow lights below to illuminate the flapping plastic. Instead of an open flame, I was thinking that I should aim for something more like a pot belly stove where the flames are light reflected off the inside and seen through the grating of the door. In other words, not so much moving flames but just the light from a fire, all without the toxic carbon monoxide that sets off the smoke detector. This would allow me to use LEDs of various colors with no moving parts.
The LEDs I´ve been using are directional, and six of them aimed in the same direction give a beam that is too tight, so I tried experimenting with a diffuser made of a discarded custard cup of milky plastic (washed out, of course). A lot of the light still shines right through the plastic and onto the ceiling, so I tried a second cup on top of the first. I still have a way to go before I get the effect I want.
I still have to come up with an enclosure. I thought that a pot belly stove was too big, so I should use something smaller, maybe a papier maché pumpkin for Halloween, but I don´t have one of those available, and I know I won be able to buy one until next fall. Maybe for now Iĺl cut out the bottom of a gallon plastic milk jug and put it over the whole thing, and see how it looks. This is becoming a work in progress.
The circuits take 9 volts DC at a few tens of milliamps, so I have to find a 9 volt power supply that really puts out 9 volts. Most unregulated wall warts put out half again as much, or 14 volts at low currents.I may stick a 7805 on the wall wart, with a pair of resistors just like a LM317. Some people don’t know that you can use a 7805 in this manner.
Back to experimenting…