Quick question about Pragraphix LED tape

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TurkeyVolumeGuessingMan
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Quick question about Pragraphix LED tape

Post by TurkeyVolumeGuessingMan » Wed Feb 08, 2017 9:19 pm

So I bought some of this great LED tape from Cult TV Man at the WonderFest last summer. It says that there's no need to be concerned about calculating resistors. But shouldn't the number of LEDs affect how the light shines? I would think that the length of the tape and how many LEDs are lit would affect the necessary resistance. How does this work, anyway?
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Mr. Engineer
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Post by Mr. Engineer » Wed Feb 08, 2017 9:53 pm

The Paragrafix LED strip uses 12 volts, can be cut at every 2-inches and has current-limiting resistors built into it.

Based on this fact, each LED cluster (of three LEDs) would be connected serially and has ONE resistor per cluster. You can then control the brightness by adjusting the input DC voltage from 6 to 12.

Or alternatively, use PWM circuits to fast flicker the LEDs thus fooling your eyes (Persistent of Vision) that they're constantly ON but in reality, is not.

[Edit]
The longer the LED strip is, the more powerful your power supply will need to be in terms of pumping more current.
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Post by TurkeyVolumeGuessingMan » Thu Feb 09, 2017 1:53 am

Mr. Engineer wrote:The longer the LED strip is, the more powerful your power supply will need to be in terms of pumping more current.
OK, thanks. That's what I needed to know. I am working on lighting up ships from the old MPC Hoth Rebel hangar diorama. I've done the Rebel Transport with regular blue LEDs (I've shared this in another thread on here). What I am wanting to do next is use a section of the LED tape from Paragraphix to light up the Millenium Falcon. I will only use a small 3 LED segment.

Eventually when I build my 1:144 Fine Molds Falcon, two segments of LED tape (6 lights) will fit perfectly for the rear thrusters.
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Post by Mr. Engineer » Thu Feb 09, 2017 9:45 pm

No problem, Greg.

You'll only need more current when the strip is more than a few metres long. I've been playing with the 1/144 Milllenium Falcon two years ago and have almost completed designing the circuit board for it. But I did not have the chance to get the shops to prototype the board for me due to my (current) Job away from home. But in all, the LEDs were designed for parallel lighting since I love to work in low voltages. Higher voltage means brighter LEDs and all but this also generates heat which worries me when it comes to scale modeling.

Using the LED's hotspot properties, I can get away with about a few LEDs to make a consistent bar of light but I cannot remember the exact number as the model was very small and so long ago.

I understand what you're trying to do, which is called (in my own terms) Scale Lighting. Understanding what each LED can do and work with its characteristics/flaw is quite interesting!
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Post by TurkeyVolumeGuessingMan » Fri Feb 10, 2017 2:05 am

I've got another question: these Paragraphix LED Tape connectors are compatible with any LED tape, right? It's all the same, I hope.

This project of mine will incorporate straight 3mm LEDs, LED tape, and fiber optics. I plan to use fiber optics with a red LED to light the engines of the tiny X-Wings.
Greg
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Post by veedubb67 » Fri Feb 10, 2017 10:03 am

Yes, they should work just fine since there's only 2 connections (positive and negative).

I've used Paul's LED tape on several of my builds and have had good success running them on 9V.


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Post by TurkeyVolumeGuessingMan » Sun Feb 12, 2017 7:18 pm

Thanks. I wasn't sure if LED tape came in different widths. I have a lot of those connectors, but it turns out that I won't be able to use one for my first model kit using the tape. I'll have to solder the wires to the contact points. Badgrendels has a tutorial video on how to do this on YouTube.
Greg
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Post by Mr. Engineer » Sun Feb 12, 2017 11:30 pm

If I am not mistaken, these LED strips comes in 10mm to 12mm widths and the really thin ones (like a stick) would be about 2.5mm wide.
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Post by brt » Mon Feb 13, 2017 12:36 pm

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