help with an LED lighthouse...

[pedalinbob]

i was recently married near a lighthouse, so my brother/best man built a nice 4ft tall lighthouse. it has a 7w incan bulb in it, and runs on AC power.

here is my problem: i have no easy way to get power out to where i want to put it in my back yard...so, i would like to use LED's...but i would like to do something special.

i have some old (but still bright and functional) malibu landscape LED lights with a solar panel. the solar panel charges 2 c size bats. at night, the lights turn on automatically. there are 4 yellow led's total, which are plenty bright.

goal: use the solar panel/LED's to light up the lighthouse...this i can easily do.
BUT, i would love to make the led's slowly flash, or (even better yet) gradually dim on and off, to give the illusion of the light rotating.

i have limited electronic knowlege...any ideas as to how i can (relatively easily) achieve this effect?

thanks in advance,
Bob

ps wasnt sure where to place this topic...

 

[linearintigrator]

in the lighthouse i built, i used a LM3909 flasher IC. and to get that rotaring efect all you have to add to the basic set-up is a 100 ohm resistor and 2200uF capacitor in series between output pin 2 and pin 8. 2---/\/\--+](---8
pin4 is ground pin5 is positive LED goes between pin6 and pin8. hope this helps, dave.

 

[pedalinbob]

sounds interesting--not sure if i understand, but i will give it a try!

sooooooo, i will get a LM3909 flasher IC.

then, i will place a 100ohm resistor and 2200uF capacitor in series between pin 2 and pin 8 (i assume the "M" thing is the reistor, and the +]( is the capacitor...does the capacitor go a certain way?)

then i will attach the ground/negative lead to pin 4, and the positive to pin 5.

then i will place the LED between pin6 and pin8 (which side is positive, and which is negative? can i use 4 LED's in parallel?).

thanks for all the help!

Bob

 

[carbonsparky]

You may have some problems finding a LM3909. I beleive they are not being made anymore. I have 5 or 6 sitting around somewhere if anyone is desperate to have some.

You might try something based off a LM555 timer. Radio Shack covers the use of this chip in their book, Timer, Op Amp and Optoelectronics (part # 62-5032). There is a low power CMOS version that sould go easy on the batteries. This chip is as easy to use as a LM3909 and is very common. If you do a Google search of "555 timer" you are bound to find more than a few sites that have circuits.

 

[Doug Owen]

So I've got a couple of ideas for discussion.

First off while the the ramp up and down simulation idea is keen (and I seem to recall a common part the model railroad types are fond of for the use), perhaps something other than mindless 'rotation' is in order? Real world nav markers typically flash their ID. That is a buoy has a Morse 'call sign', it might flash a Morse R (short long short) to make it easy to sort out from the rest. That's how it's shown on the charts, right next to the light, details of it's signature. Some are numbered, 1-4-2 (flashed once, pause, four times, pause, twice) is a recently saved Lighthouse somewhere 'back east' (Boston?), the locals demanded the "I love you" light stay......

Anyway, for either, how about the 'solid state tape recorder' ICs used in answering machines and the like? Jameco will sell you one for under $10 that will store 240 seconds in EEROM (needs no power to 'remember') on board. All you do is either 'record' a CPO (Code Practice Oscillator, a key making tones) or an audio generator as you sweep the volume up and down. On playback you demodulate (level detect the AC) and drive the LED level appropriately. A simple rotary switch on the address control lines could allow you to program several patterns, each of which would repeat every minute or so, just like the real thing.

How's that suit ya?

Doug Owen

 

[highlandsun]

Doug, you have some seriously cool creativity...

 

[Burnt_Retinas]

Doug,

A cool idea indeed. The sweeping of the amplitude would nicely give the desired effect. The extras are a bonus. I like it!

Chris

 

[linearintigrator]

if you go the LM3909 route, the /\/\ is the resistor, the capacitor negative goes to pin 8 and the LED anode (long lead) goes to pin 6. i would use a cap. with a voltage rating of at least 25VDC. overkill never fails! if you need help with parts, i have a 35 year collection in the basement that doesn't get much use anymore. dave

 

[pedalinbob]

wow, you folks are great--incredibly creative!

im still reading!

Bob