D-7 "The Build"

[Grendels]

You want to wire up all LED's in parallel, not series. The reason why is that if you have one LED burn out in series the entire circuit goes dark. That is what is wrong with so many strings of Christmas lights. One bulb burns out and you have to check every single one of them to see which one is not working.

In parallel each LED sees the same voltage. This is good because if one shorts, the others keep on going. This is bad because you need to put an resistor on each LED.

As for placement of the resistor with the LED, it really doesn't matter if it goes on the + or - end of the circuit. The job of the resistor is to lower the current that passes through the LED, so it won't burn up.

A good analogy is to look at a water hose with a sprinkler. A open the valve to full and there might be too much water for the sprinkler head to work correctly. But if you insert a kink in the hose, then the water at the sprinkler head would have less energy, and can work properly.

Think of the resistor as a kink in the hose when watering the garden. It doesn't matter where that kink is, the sprinkler won't see the full current of the water in the hose.

 

[Kryptosdaddy]

Grendels, I'm a plumber- that analogy cracks me up! LOL- but i do see your point. What I'm doing is lighting a kit that i will have no access to the inside when done, so parallel is the key. I have checked some info out earlier, but I never quit asking questions.

And thanks for those links Glorf! Be good! ;D

 

[trekriffic]

For large numbers of LEDs I've seen circuits that are hybrids of parallel and series. You have the main parallel bus which is running strings of series circuits off it; however, the number of LEDs in each series is limited by the voltage you have available. So if you are running 6 volts from the wall or batteries you can only wire up 2 LEDs in each series; 3 on a 9 volt circuit; and 4 on a 12 volt circuit. The nice thing is each series only requires one resistor for the first LED in each string. It gets a little complicated.

 

[Grendels]

Grendels, I'm a plumber- that analogy cracks me up! LOL- but i do see your point. What I'm doing is lighting a kit that i will have no access to the inside when done, so parallel is the key. I have checked some info out earlier, but I never quit asking questions.

And thanks for those links Glorf! Be good! ;D

Make sure you run your lights for a while before you seal her up. If any problems will occur, it should be in the first 10 hours or so. If you are using LED's then that 10 hours will not harm their life at all. Wired properly, they can last for 8 years left on continuously.

For large numbers of LEDs I've seen circuits that are hybrids of parallel and series. You have the main parallel bus which is running strings of series circuits off it; however, the number of LEDs in each series is limited by the voltage you have available. So if you are running 6 volts from the wall or batteries you can only wire up 2 LEDs in each series; 3 on a 9 volt circuit; and 4 on a 12 volt circuit. The nice thing is each series only requires one resistor for the first LED in each string. It gets a little complicated.

Be careful with this. Yellow LED's do not want more than 2 volts through them, so on a 6 volt circuit you can have three of them in series. If you put two, you will burn them up. Different colors use different voltages.

 

[Ziz]

In parallel each LED sees the same voltage. This is good because if one shorts, the others keep on going. This is bad because you need to put an resistor on each LED.

Shouldn't you be able to solve both problems at once by doing it as a bus circuit? Put the single resistor on one pole of the power source and then have long positive and negative leads that the positives and negatives of the LED's feed off of.

 

[Grendels]

The equations that control this say that only one resistor will work. But there are difficulties with that. First, common resistors for this purpose are only 1/4 watt. This is fine if you are using one per LED. But if you use one resistor for all LED, that 1/4 watt resistor will burn up really fast. You need a much larger resistor, one that can handle say 1 watt, or 2 watts. It depends upon how many LED's you are using and how much current they are pulling. There is quite a bit of math involved in figuring out the correct size resistor both in resistance and power handling abilities.

One other problem with the one resistor method is heat. A large resistor with a lot of current is going to get hot. (This is how electric stoves work. The burner is one very large resistor) Now you will have one big hot spot instead of many smaller ones. Heat will build up really fast in that one area of the model. Not good. You can move the resistor outside the model and put it near your power supply but it will be hard to disguise the resistor. You can't paint it, paint will insulate it and hold in the heat, bringing it near burn out much quicker. The same thing happens if you put it in a box, it just traps heat.

One solution is to limit yourself to less than 15 LED's, use two AA batteries to power them, and only use white or blue LED's. No resistance is needed this way, and if you need different colors, just paint them with transparent paint. Two AA batteries can power 15 LED's for at least a day.

 

[Glorfindel]

I knew you needed someone with better knowledge on electronics then me. I still make lights with my Zippo.

 

[smusno]

Tother end!

The nose, is turning into a bit of a pig. Theres not allot of room for 3 bulbs, and id like a 4th, and a red for the torpedo tube.

ps, this isnt glued, its held together with clothes pegs! So, I know i have a ton of blocking to do!

 

[Igard]

Nice glow! I miss lighting things already. ;D

 

[smusno]

Nice glow! I miss lighting things already. ;D

Well, after this one, I have a Revell 1701 to do (cant wait to weather her, and really get to grips with the airbrush), so more LED's (and a possible spinner kit (suggestions anyone?)

And I shall be purchasing a lighting kit for my 1:350 next month too!

 

[Glorfindel]

Dave there is a spinner kit out there for that effect. For the life of me I can't remember the company's name.
Ah' I've remembered! Madman Lighting. I think it's the deluxe spinner that you want.
http://home.comcast.net/~johndavidcook/delux-spinner.html
http://home.comcast.net/~johndavidcook/index.html
http://www.youtube.com/user/MadmanLighting
Hope these help.

 

[smusno]

;D

 

[Igard]

Superb. She's coming together nicely.

 

[smusno]

I posted in the review section by accident :

but im still back.

 

[ModelMakerMike]

She is looking beautiful. Love the green glow!
Can't wait to see her completed, and on the hunt for wary Federation or Romulan ships.

;D ;D ;D ;D

 

[smusno]

right, back on the build bus.

Firstly, the "head" and neck are a pig seam wise. But, i shall conquer!

then................ lights

Oh, and, as it's a Revell kit. I thought I might give there colours a bash.

Never again

As for colours.............. think matchbox

thats all for now.

 

[smusno]

I quick question though.

can you mix chrome/steel colour paint into normal colour paint to give it a metallic fleck?

 

[Husker Adama]

I've done it before with a high gloss color. Silver can go with a glossy gray but if its flat it wont work as well.

And obviously, dont' mix acryl with enamel.

 

[greyphantom1000]

love the engine lights

 

[Igard]

Good job with those seams. I had some problems their too, but I actually learned alot from working on this model. Seams no longer frighten me quite like they used to (famous last words).

Where did you get your LED tape? I've been looking for a UK supplier of that stuff.