85-LED circuit. . .

[MillenniumFalsehood]

Okay, this ship I'm building is going to be the ulitmate Romulan Bird of Prey, and I made a short list of all the features it will contain:

Landing bays (2)
Functioning Landing gear (3)
Running lights (space)
Running lights (Atmosphere)
Impulse engines with variable color and intensity
Warp engines with variable color and intensity
Lit sensors and windows
Lit Plasma weapon

The thing is that with all the different colors and features, the LED requirements shot from the bare minimum of four to five LEDs(One for the sensors, one for the impulse, and two for the warp engines; another one if you want a light plasma weapon) to EIGHTY-ONE FRAKIN' LEDS! Here's how the distribution goes:

Sensor lights: 2 5mm white LEDs(one for the dome and one for the saucer)
Window lights: 4 5mm white LEDs
Plasma weapon: 1 5mm white LED, 1 5mm yellow LED, and 1 5mm Red LED
Landing bays(each): 1 5mm red LED, 1 3mm red LED, 1 3mm white LED
Landing gears: 13 3mm white LEDs
Running lights(space): 4 3mm green LEDs, 4 3mm red LEDs, 2 yellow 3mm LEDs
Running lights (atmosphere): 7 3mm green LEDs, 7 3mmm red LEDs, 5 3mm yellow LEDs
Warp engine (each): 1 5mm red/green/blue combo LED, 1 5mm red LED, 1 5mm green LED, 1 5mm blue LED, 1 5mm white LED, 1 5mm yellow LED, 1 3mm red LED, 1 3mm green LED, 1 3mm blue LED
Impulse Engine(each): same as warp engine

In the engines, the 3mm LEDs are driven by a chaser/blinker circuit and the 5mm LEDs are for the background color, with each color being independantly controlled. The higher amount of running lights for atmosphere as opposed to space is because UFOs usually are reported to have a lot of lights on the belly, but not so much on top. The different internal rooms(the landing gears and two landing bays) would be independantly controlled. The plasma weapon's LEDs are also independantly controlled

The problem I have is how to distribute the voltage so I don't overdrive and fry the LEDs(especially the finicky 3mm types). I would rather have them in paralelle than series if I can help it; I plan on the body containing the power source, so I can't use any battery beyond 12 volts. Could someone help me please? Or at least draw a diagram. . . I have seen circuits with comperable numbers of LEDs, but I can't figure out how to connect them.

[jwrjr]

If you use a resistor with each led, power distribution is not a problem. My refit has 208 leds, with 208 resistors. Works fine.

[en'til Zog]

Hm... 81 LEDs taking about .020 Amp each is... 1.6 amps total if you are running 'em all in parallel. That's a lot of amps.

Now, if you make up a set of SERIES sets you can reduce your amperage needs by quite a bit.

For instance: 4 green 3mm LEDs in series would use up (about) 8 volts depending on the voltage needs of the green LEDs. So instead of needing 0.080 amps for the 4 in PARALLEL, you need only 0.020 amps for the 4 in SERIES.

Each SERIES string needs it's own proper resistor, of course.

By combining the like kinds of LEDs into PARALLEL sets of SERIES strings you can keep your battery and power requirements down. As long as each SERIES string uses less voltage than your power supply supplies, you should be fine.

That's one technique I use to keep from imploding my power units.

[MillenniumFalsehood]

Hmm. So I should do as follows:

Running lights(space):
String1 Green 3mm LEDs
String2 Red 3mm LEDs
String3 Yellow 3mm LEDs
Running lights(atmo.):
String1 Green 3mm LEDs
String2 Red 3mm LEDs
String3 Yellow 3mm LEDs
Etc. . .

I would then have all 3mms and 5mms on individual strings, right?
And each string would have it's own resistor, correct?

If so, then would this be a good plan(sorry about the size)?

[Sparky]

that diagram looks promising, I couldn't zoom in but you are on the right track.

It is also worth noting that if you get your LEDs from a place like Digikey you can find reds, greens, and yellows that use the same current (in steady state).

So you could hook them all in series since the steady state current through the loop won't exceed the rating of any of the LEDs. I don't recall that whites and blues will match the colored LEDs even from the same series of a particular manufacturer.

This will help with what you'd like, a single loop of lights for space, and another single loop of LEDs for atmosphere.

Your best bet is to look through a search on their site, of LEDs meeting your basic requirements (3 mm with legs).

[MillenniumFalsehood]

I was thinking of getting the 5mm whites and blues from All Electronics since they are having a sale of Whites $0.65 and Blues $0.55. Are there any sources with cheap 3mm whites? They are $2.85 a piece from AE and it would be nice to get some cheaper than that. Also AE has another sale on multi-color LEDs that flash red/blue/green then fade red/blue/green that I'm going to use in the engines.

If you want I can send you the original document via e-mail, since I made it on paint. I can't calculate resistor values yet since I don't know the values of the LEDs I'm using. But if it helps the pot trimmers I'm using are 100k.

[en'til Zog]

Looks good. One thing to make sure of? That the voltage you're supplying to all this EXCEEDS the voltage needs of your most needy string.

F'r instance - 7 GREEN LEDs in SERIES - if they each need 1.8 volts (some do, some need more) the STRING needs 12.6 volts. If they need only 1.7 volts each, the string will use up 11.9 volts. (No resistor is needed if you're feeding everything with either a 12 volt battery or a 12 volt REGULATED DC wall wart or mains converter.) Actually, if they 'need' 1.8 volts each, they'll be a bit dim at 12 volts so check the actual srting to see how bright it is BEFORE stuffing anything into the ROM-BOP. Checking before stuffing is ALWAYS a good thing to do.

Do you have an "Experimenter's Bread Board" to try out circuits? Very handy things. (See the top two ANNOUNCEMENTS in this forum.)

What do you do if the green LEDs need more than 1.8 volts? Use a sligltly higher voltage power supply, or break the strings down into shorter (lower voltage) series strings. Or try your wall wart with the 7 LED strings and see if they're "bright enough" for you.

I can't get the 'full size' schematic on that link, just the small one, so I can't read the notes on it. If there is a string of 5 WHITE LEDs you will need 18 volts for the string, since the average WHITE LED needs around 3.6 volts. Something to think about.

Then TEST AGAIN with ALL the LEDs going at once to see if you're still happy with the whole thing since the more LEDs you add, the more power is needed and the more the 'regulated' voltage will be drawn down to it's actual rating. (I've found that even a 'regulated' supply can put out a little more voltage than it's rated for if there's very little current being drwan.)

Over to you.

[MillenniumFalsehood]

Hmm. In that case I'll break down the strings into four or five per string for the regular colors and about two or three for the whites and blues. If you want I can e-mail the full scale plan to you or draw a new one. I do have a breadboard so I can try different LED combinations and use digital meter to test the resistance of the LEDs.

I'm going to try this weekend to get the formation lights and interior lights(minus the landing gear wells) working at least. I have a shortage of white LEDs at the moment, unfortunately.

I'm going to order the 5mm white LEDs, multi-color LEDs, and potentiometers that I need from All Electronics this weekend and hopefully they will arrive sometime next week. After that I'll try the engine lights.

[en'til Zog]

ALL is one of my very favorite toy stores, right next to the SSM store.

With this comlex a lighting layout, you might need to use a batch of variable resistors to 'tweak' the light levels of the different strings of LEDs. Fortunately each string will be passing only 0.020 amps which should allow you to use cheap variable resistorizers.

And, yes, if you need just send me the scram-attic.

[MillenniumFalsehood]

Had some time this afternoon and drew a new plan.

A few things about this one:

The circuit diagram had too many LEDs on the string for the amount of voltage I am going to use, so I split a few of them up into different strings.

The chaser circuit in the old plan had the activation switch on the wrong wire(the power bus, not an independant circuit), so I fixed that.

The old plan was completely missing the plasma torpedo circuit, so I put that in.

And(most obviously) I upped the size so you can read the notes.

I'll try to test the LEDs I have this evening and develop a more detailed plan based on the average amps and voltage that they will require(I may need some help on this one; I'm still trying to figure out this new digital meter. . .).

[Sparky]

That looks really good. Thanks for upping the size, one question before I look more closely: What is your plan for the switches? This not a criticism, I'm just thinking about all the tricks folks have used to hide switches on a model. . .

[MillenniumFalsehood]

Well, since there are absolutely no greeblies on this ship whatsoever I'll put them on the inside of the model. The top dome lifts off and there is a light-blocking layer below that, like a double hull on a submarine. The light-blocking layer will contain the switches, have the toggles of the switches poking through, or I'll put in a hatch to gain access to the switches(it depends on how deep I can go with it). A diagram is in order here.

[MillenniumFalsehood]

I wired up the plasma torpedo circuit this evening and everything works. The LED assembly will be mounted in a light box and that mounted on the aperature. It should look believable when finished. I'm going to order the LEDs and other components tommorrow and they should be here next week. Then I can tackle the really fun parts: the engines.

[en'til Zog]

LEDs! Greeblies! YAY!

ahem...

One trick with each string of LEDs - put a meter in SERIES with all the LEDs in the string & the variable resistorizer and adjust the variable so the total current flow is 0.020 Amps or 20 milliAmps in each string. Or whatever you choose - 15 mA would be dimmer, but use 1/4 the power of a 20 mA circuit. And the LEDs should last (effectively) forever.

GO FOR IT!

[MillenniumFalsehood]

For the running lights I'll probably put in the full 20 mA, since they have to shine through the hull(You never see them on the studio model like you do with the Enterprise, so I figure if they do have anti-collision lights they are some sort of EL paint; I'm trying to replicate that by drilling the hole in the hull, mounting the LED in it, then cutting it flush with the hull; they will actually shine though the paint). I'm using super-bright 3mm LEDs for this so they have maximum visibility(a quality that real anti-collision lights would be expected to have).

I have to attend a 50th wedding anniversary today in Wichta, so I'll drop by the Hobbytown there and pick up the paints I need. I'll probably get Testors paints because MM grays have too much green tint for my tastes. I'll see if they have any 1.5mm fiber optic filament on hand(the filament needs to be this thick so it will be in scale with the portholes).