Lighthouse Simulation

[Spaceman Spiff]

I've read several threads posted here regarding simulating the effect of a lighthouse's light from dim to bright, then back again. I, too, have a project where I'm building a replica lighthouse for a church and need the effect of the light automatically cycling in brightness.

Although these other threads discussed various options, I found an interesting circuit that seems to electronically simulate a lighthouse most accurately: http://www.discovercircuits.com/H-Corner/ho-train-lite.htm

I like the way this circuit ramps the light brighter, then steps the brightness high to simulate the beam being directly in front of the eye, then steps it downward again, and finally ramps it back down. However, the circuit appears to be limited to a small LED, and I need something much larger.

My lighthouse is about 9½ feet tall, and I'd like to use a 15W - 25W incandescent bulb for the light. I'm looking for any help where I can use a larger light.

 

[philba]

That's a cute circuit. I've had trouble getting dave johnson's circuits working in the past though this one seems pretty straight forward.

I dont think the circuit scales well to incandescent lights. A 12V system would draw 2A at the brightest for a 25W bulb. I'm not sure what the dimmer part would draw but I bet it would be in the .5 to 1A range. Since the transistor would not be in saturation, it would run pretty hot. For a bulb in that wattage range, I would use a PWM circuit, probably driven by a uC.

However, in that size, why not get a small gearhead motor and rotate a reflector? Then it will be like a real lighthouse.

 

[justDIY]

how about a 25 watt spotlight bulb, an old electric clock motor and a mirror glued to a piece of wood.

hook the mirror to the second hand of the motor, and rig the spotlight inside the model somewhere to shine on it.

or any auto parts store should be able to get you a cheap version of these:
**broken link removed**

 

[stevez]

The color of the filament will change as the voltage increases or decreases - along with the apparent brightness. If the color change doesn't bother you then simulating the dim-bright-dim is a decent approach.

 

[Spaceman Spiff]

The best suggestion seems to be for me to just buy something. I searched the Internet using "rotating beacon" and "lighthouse" and found a company selling rotating lighthouse beacons. Since this effect would be the closest to real, I guess I'll go with it. Thanks for all your suggestions.

**broken link removed**

 

[bigkim100]

Ooooh...are your neighbours gonna love you!

 

[kcflyer]

I'm building one, too (see my other post). I decided to go with a 555 timer into a 4017 decade counter, which drives a circular array of super-bright white LED's. I've also found a place where I can get reflectors for mini-maglites for each of the LED's. The circuit is relatively straightforward. I've tested it on the breadboard and am in the process of soldering it more permanently. I'm also using a 120v photocell switch to turn on the power when it gets dark.

I think it will look very cool, will simulate rotation nicely, and doesn't have any moving parts to wear out. I think the white LED's will be bright enough to be noticed, but not bright enough to be annoying. Of course, you could use any color you wanted, or even a combination.

To make the beam a little broader and brighter, I'm using an array of diodes ahead of the LED's so that two neghboring LED's will be lit at one time as it circles around.