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Tamiya A10 leds


Anth

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Hi guys well building a thunderbolt a10 from balkans war, i saw them when i served and always wanted to do one so got myself a 1/48 scale and half way through and decided to put some leds in with fibre optic lines to the tail and wing tips, i looked aroud the web and see this has been done before to great effect by some better builders than i,  but hey ho, so my issue is ive  a few  3volt leds various colours green red white  blue you get the picture and loads of 1 mm and 0.5 mm fibre optic,.  Now i wanted to run 9 volt power  in parralel or series , but 9 volt series wont run 4 leds and in parallel id need a resistor, i get that much but every time i do a callculation for the resistors i get a different size??? Am i loseing it,?  So 4 0r 5 3 volt leds all at 20 mha rateing  run on a 9 volt power source needs wot size resistor??? Any help or ideas would be a big help  cheers 

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It did scotthldr  yes,  so i worked it out myself in the end  but mistakenly i just presumed one person has put an led into a model    be it a car train or the millenium falcon lol so apologise for presumeing  , i would of settled for sorry pal cant help but wish you luck lol,,, 

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1 hour ago, Anth said:

but mistakenly i just presumed one person has put an led into a model

Who may not be visiting daily, or not even be interested in modern aircraft preferring earlier types. 

 

There's absolutely no need for remarks like 

Quote

but  does not bode well for this comunity   closed shop eh,,, 

 

Good for you that you've found a way to solve your issue regardless.

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Sorry but can’t be of help on the resistors but I was wondering why not run poco leds down to the wing tips rather than fibre optic?  They are tiny & you can buy them with resistors attached.  I am toying with using flashing leds to represent strobe anti collision lights too.  A 1/47 A-10 is quite spacious inside provided you don’t upset the CoG.  My previous built in lights have been cut down pound store leds and even those work at a pinch

 

Standard cheap leds in a 1/48 Harrier

 

3AnPpsk.jpg

 

Pico leds for size - left standard light, right flashing

 

QTYg0So.jpg
 

TzxVAkz.jpg
 

So sorry my post doesn’t answer your question but just offering what I know 

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On 02/11/2021 at 18:17, Anth said:

???? 75 views and not one response 🤔so am i in the wrong place,  well i worked it out myself thanks, but  does not bode well for this comunity   closed shop eh,,, 

Its not a closed shop, if someone felt able to help then they would chime in.

 

You cant expect people to say "sorry I cant help you" in every thread they read and cant help with.  80% of the threads I read I cant help people with so would spend all my time saying that.

 

Julien

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On 11/2/2021 at 7:17 PM, Anth said:

???? 75 views and not one response 🤔so am i in the wrong place,  well i worked it out myself thanks, but  does not bode well for this comunity   closed shop eh,,, 

hmmm a bit harsh, no?

 

maybe also not the most appropriate thread and thread title!

I 'd assume your LED resistor issue has not a lot to do with you wanting to install it in a TAMIYA A-10 kit. in the MODERN military aircraft modelling forum...

I suggest you search for a more appropriate title at least so that LED and resistor specialists see your needs already from the title! :thumbsup:

 

I personally probably could helped you with a modern A-10 related question only, sorry! I did not even get that led is LED from the title.... :(

 

 

 

 

 

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Thanks for the input guys, its sll cool tho sorted  

Barside thanks mate i did think about pico leds but could not find any at the time so just went with wot i had, and had akready drilled a 1 mm hole in the wing tips for the fibre optic , in the end i buikt a small light box with a 3 mm flat white led drilled a few 1mm holes in opposite end and fed the fibre optic to the tail  both sides, the nose and behind cockpit the wing tips are fed via seperate leds green and red and fibre optic to the wing tips all of this neatly mounted inside the fusalage  with a 9v battery via a jack plug connection with battery hidden inside a a fuel truck the hose used has the power lead inside, so in the end  9v power via an 68oahm 1 watt resistor to the leds linked in parallel circuit  looks realy nice just a few little bits to complete and shes done,  but again thanks for those that took an interest in wotever shape or form.... 

And maybe i could of worded the heading a bit better but again  

In my deffence an a 10  thunderbolt is fairly modern aircraft id say, and once read, even i kinda got the jist,,,,????    Again im fairly new here so i may obvoiusly be in error,,

 

Does anyone know if there is a rubber tyre upgrade with wheels or not, for this  tamiya a 10 kit,, not impressed with plastic tyres tho 😕. Again appologies if i rufgled feathers so to speak and enjoy 

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Sounds good.  I have a few with leads routed through gpu ports to an eternal battery pack.  Might look at putting a battery inside one soon but conscious of the centre of gravity- don’t want a tail sitter!

Quick look on eBay has Reskit resin replacement wheels.  Look to be a bit pricey but depends where you look

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2 hours ago, Anth said:

Does anyone know if there is a rubber tyre upgrade with wheels or not, for this  tamiya a 10 kit,, not impressed with plastic tyres tho

Not rubber (rubber tends to be tricky as it can leak oils over time), but resin. The mentioned Reskit wheels come in a complete set.

154496_0.jpg

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LED Calculations

 

An LED has a specific voltage across it, which varies by colour but typically it is in the range 2v to 3v.  The traditional red and green are about 2v, but the blues and whites tend to need a higher voltage.

 

You can run them in series or parallel - if in series add the LED voltages and your power source needs to be greater, ideally only by a small amount.

 

An LED needs a current through it, the higher the brighter - typically you are talking 5mA to 30mA - as a rule of thumb start with 10mA and see if that is bright enough.

 

In most cases you will need current limiting resistors.

 

Say you are running one LED and it needs a voltage VL.  You have a power source VS.  VS must be bigger than VL.

 

You want a current IL to flow through the LED and to fix this you will need a resistor.  The resistor has the voltage difference across it (VS-VL) and has a current IL flowing through it.  Using Ohm's Law the resistance is

 

R = (VS-VL)/IL.

 

So for a Green LED, with a 5V source and 10mA this would be (5-2)/0.01 = 300 ohms

 

If you are running a number of LEDs in series, just sum up the LED voltages so VL = (VL1 + VL2 + VL3) and use the equation above.

 

Running in parallel, you could treat them as a load of paralleled up series circuits and put a resistor in each series circuit as above.  But if the paralleled LEDs are all similar (so have the same voltage you can get away with using one resistor.

 

Say you have three green/red LEDs in parallel.  Here the voltage across the resistor is VS-VL but the current for all three LEDs flows through it - so 3 x IL. So the equation becomes

 

R = (VS - VL)/(3 x IL)

 

So for three green LEDs running on off a 5V source you have

 

R = (5V - 2V)/0.03A = 100 ohms.

 

I said that ideally you want to have a voltage source only slightly higher than LED voltage - this is because voltage across the resistor is wasted power, all it does is heat up the resistor - and it can get to the point where the resistor will get very hot.

 

Example - 3 green LEDs in parallel

 

5V power source - I = 30mA, Power wasted in the resistor = V x I = (5-2) x 0.03 = 90mW (a small resistor will remain cool)

9V power source - I =30mA, Power wasted in the resistor = V x I = (9-2) X 0.03 = 210mW (if you are using a small resistor it will get hot)

 

Cheers,

 

Nigel

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On 02/11/2021 at 19:17, Anth said:

???? 75 views and not one response 🤔so am i in the wrong place,  well i worked it out myself thanks, but  does not bode well for this comunity   closed shop eh,,, 

nheather pretty much gave the answer, but a different headline like "How do I calculate the Ohms when wiring LEDs?" instead of "Tamiya A10 leds" might have attracted the right experts a little sooner.

 

As an exception: Do not read https://en.wikipedia.org/wiki/Light-emitting_diode or https://en.wikipedia.org/wiki/Ohm's_law both are more confusing than helpful.

 

This one is a nice shortcut: https://ohmslawcalculator.com/led-resistor-calculator

 

Keep in mind: Resistors come in "odd" values (to the unsuspecting observer, there is a hidden pattern behind the values (do not read https://en.wikipedia.org/wiki/E_series_of_preferred_numbers )) and they do have bigger tolerances than you'd expect (don't buy expensive precision resistors with "even" values), but for some reason the system works.

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