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Discussion Starter #1
I wish there was a book or chart that said in plain English that when you use this LED with this battery you use this resistor and when you use this number of lights with this battery you use this resistor and you you put it here. I don't want to be an electrician i just want to light some models.
 

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I wish there was a book or chart that said in plain English that when you use this LED with this battery you use this resistor and when you use this number of lights with this battery you use this resistor and you you put it here. I don't want to be an electrician i just want to light some models.
Hi :wink2:
YES!! a "Basic-Tutorial" on the subject, with lists, charts, cave-drawings, ect..
would help a lot of Us "Tech-Challenged" out here..
along w/ using 12 volt 2 -4 Amp up to 22volt 2 -4Amp Values
(for Us "slot car dudes" >:) )

TY!! in advance,

Bubba (The Senile Tech-Impaired) 123 :wink2:
 

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LED's are not hard to wire.
You just need to know the voltage of the LED's and the power you want to use 12v 9v etc.
The amount of LED's dictates what type circuit you use Serial of Parallel.
Here is some good info for you. http://nuigroup.com/forums/viewthread/1030/
The one thing I would do not shown is use a resistor for each LED. Especially if you use different color LED's
Make sure you add up the total amperage the LED's will draw and use a power supply with more than needed.
Most LED's draw .20 mA. SO if you have 20 LED's they draw 400 mA and I would use at least a 500 mA power supply.
Bigger is no problem but one just big enough will run hot and not last.
 

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Well, you need to know some basic info about what LEDs your going to use, have some basic soldering equipment, etc.
Go here and input your data.
LED series parallel array wizard
I use that when wiring in one type of circuit,which is usually parallel.
There is also one for using series and parallel together that I have used.
It allows you to wire a number of LED's in series chains then connect the chains in parallel. I have it saved on my PC but not on my phone. It is just another option.

Edit: The led wizzard linked above is the one I used for combining circuits.
Here is one for finding the right resistor for individual LED's. http://led.linear1.org/1led.wiz
 

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Discussion Starter #6
what is "diode forward voltage, diode forward current" and where do I find this info for different size/color LED's? Yes , I am just one step above stupid.
 

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Forward voltage is the volts needed to run the LED. Most LEDs are 3v but some colored ones may be a bit less, like 2.5v or even 1.8v. It should say on the package. Forward current is 99.9999 percent of the time going to be 20mah.
 

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mA is thr current the max current the LED is rated for.
As stated most are 20 mA.
I would suggest sticking with white LED's and using clear color paint on the lens instead of colored LED's.
That way you only need 1 size resistor instead of multiple values.
When you get comfortable using LED's then branch out to colored ones.
I went to using only white so I can use just one value resistor.
 

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When I built this, I bought all my LEDs from the same place in China off eBay. I bought white, red and blue. They came pre-wired with resistors already soldered on. I knew I was going to use a 9v power supply so I just searched 9v Blue LED and 9v red LED. The place I found had all the colors I needed and all came pre-wired
 

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When I built this, I bought all my LEDs from the same place in China off eBay. I bought white, red and blue. They came pre-wired with resistors already soldered on. I knew I was going to use a 9v power supply so I just searched 9v Blue LED and 9v red LED. The place I found had all the colors I needed and all came pre-wired
That would be a good way for beginners to go especially if they need SMD LED's.
I prefer to solder them myself because it is much cheaper.
With those prewired LED's you just need to add up the mA for all LED's and get a power supply with more mA output.
 

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I got 50 pre-wired/resistored whites for under $5, 20 pre-wired/resistored blues for $6. Don't remember what the 5 reds cost. Again, these were from a dealer in China off eBay. I have no doubt to the quality of these cheap LEDs as my Galactica has been plugged in burning steady, since WonderFest, nearly 5 months ago!
 

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Let me add my two cents worth.

Like others have mentioned you do need to know the specifications of the LED that you want to use.
The Forward Voltage: Vf and the Forward Current If
These can be found in the data sheet of the particular LED or the eBay seller, or other on-line store, will be able to give you that information.

The calculation for a dropping resistor is a very simple Ohms law one:
Subtract the LED's Vf from your supply voltage and then divide by If and multiply by 1000.

You have to multiply by 1000 as the calculation wants Amps and not MilliAmps (mA)

Example:
You have a 9 volt power source and a LED rated at 3.2v at 20mA.
( (9-3.2)/20 ) X 1000 = 290ohms

So use a resistor of at least 290ohms or slightly higher resistance.
Do not use a smaller resistance or the magic smoke will escape from the LED and it will never see the light again.

If you increase the resistance the LED brightness will decrease which can be very useful in modelling.
There is no hard and fast rule for calculating the brightness decrease, just experiment with higher values of resistors until you get the desired effect.

Just adding to what jimkirk said about using white LEDs and coloring them with clear colored paint. (PS. I love the back end of your Galactica.)
This works very well, but choose your 'white' LED carefully.
A 'cool white' LED with some red clear paint slopped on it will reduce its brightness very significantly. 'Cool White' LEDs produce very little red. They are fine for coloring with a blue color but a 'warm white' LED is much better when you want to color it red.
Experiment!


Alien
 
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