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Author Topic: LED's for lighting  (Read 17159 times)

flag-d

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LED's for lighting
« on: April 15, 2006, 10:51:48 PM »

I have a WWII MTB and was going to fit 'grain of wheat' type bulbs for lighting (nav, mast-head, stern etc) but have 'blown' a couple of bulbs already (or they were dead in the pack).  Been wondering about using mini-LED's instead.  Anyone know if they're available complete with resistor as a ready to use package, as it were?  I have a Tamiya truck model which is loaded with the things.

Mike
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malcolmfrary

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Re: LED's for lighting
« Reply #1 on: April 15, 2006, 11:34:19 PM »

LED's without a resistor usually drop 1.9 volts when conducting at their normal rating of 10 - 20 mA.  I don't know if sub-min ones are available with a built-in resistor, but if they are, they will probably be identified by having a rather higher voltage rating. 
You do see ordinary ones being used without a resistor (like the key ring lights), which have a 3 volt supply, but these rely on the internal resistance of the battery to limit the current. 
If you try running one without a limiter from a source capable of high current, it will glow very brightly, very briefly, once.  You don't have to let the smoke out of electronic bits for them to stop working, just re-arranging it internally is enough.
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Dave Leishman

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Re: LED's for lighting
« Reply #2 on: April 15, 2006, 11:53:43 PM »

Mike - there was a thread on the old forums that dealt with this, which is unfortunately lost now, but I did manage to save off a couple of the links before it went.

LED Information and Resistor Calculator
Article about using LEDs in Model Boats on RCGroups.com
Another article on LEDs from the Model Electronic Railway Group website

I've been experimenting with LEDs and found the following ebay supplier very helpful and reliable.
Goodwill LEDs Sales

I've found that the narrow viewing angle LEDs can be used very effectively if they're encased in some form of translucent lens. I use acrylic beads (available in red/green/amber/clear and most other colours) that I turn down in the lathe, drill out for 3mm LEDs and place a brass cap on top. The brass cap reflects the light down the edges of the lens giving an all-round light.

Hope this is of some use :)
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The_Ships_Cat

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Re: LED's for lighting
« Reply #3 on: April 16, 2006, 08:14:08 AM »

www.ultraleds.co.uk has some usefull info
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Doc

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Re: LED's for lighting
« Reply #4 on: April 16, 2006, 01:47:55 PM »

The biggest problem with using LEDs is that they are not as bright in all directions as a 'bulb' type light.  There are 'tricks' to make them brighter in some directions, but, unless you're a lens grinder it may not be the easiest thing to do.
Figuring the size of the required resistor isn't difficult once you get your mind wrapped around how it works, simple math.  'Course, the 'wrapping' part isn't all that simple at times because of all the different ways of stringing them together.  (All those 'electronics' guys are a bit 'twisted' anyway, right?) 
The good part about using LEDs is that they are almost indestructable, meaning that you don't normally have to provide access paths to them.  They are also not as fragile as other 'lights'  One of the really 'neat' things about LEDs is that you can make them change color.  Not too sure how often that would be required, but it sure opens some possibilities!
 - 'Doc

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flag-d

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Re: LED's for lighting
« Reply #5 on: April 16, 2006, 10:19:38 PM »

Thanks all!  Wow!  Rapid response and plenty of good info too.  Thanks again.  Looking again at the electronics 'black box' of my Tamiya truck, I see that there is a host of resisitors fitted immediately before the connection pins: so the LED's dont have built in resistors after all!

Thanks again

Mike
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riggers24

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Re: LED's for lighting
« Reply #6 on: April 17, 2006, 10:12:57 AM »

Hi

I got these 2 pages off the old MB site, I can't remember who placed them on but they may help you
http://www.kpsec.freeuk.com/components/led.htm
http://metku.net/index.html?sect=view&n=1&path=mods/ledcalc/index_eng#series

riggers
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dpbarry

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Re: LED's for lighting
« Reply #7 on: April 19, 2006, 01:03:44 PM »

Hi Mike..

I think one of the main problems is that the LED radiates the majority of its light out through the dome on the top.  I'm not sure if the sides can be polished but would be very interested to see if it could be done.

Hmm!!.  Might just have a look at that.

If the wheat bulbs are blowing, could it be that you may be supplying too much power to them?

Just a though.

Declan
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malcolmfrary

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Re: LED's for lighting
« Reply #8 on: April 20, 2006, 11:08:33 PM »

The biggest problem with using LEDs is that they are not as bright in all directions as a 'bulb' type light.? There are 'tricks' to make them brighter in some directions, but, unless you're a lens grinder it may not be the easiest thing to do.
Figuring the size of the required resistor isn't difficult once you get your mind wrapped around how it works, simple math.? 'Course, the 'wrapping' part isn't all that simple at times because of all the different ways of stringing them together.? (All those 'electronics' guys are a bit 'twisted' anyway, right?)?
The good part about using LEDs is that they are almost indestructable, meaning that you don't normally have to provide access paths to them.? They are also not as fragile as other 'lights'? One of the really 'neat' things about LEDs is that you can make them change color.? Not too sure how often that would be required, but it sure opens some possibilities!
 - 'Doc



Hi Doc - Of course us electronics guys are twisted - it's all that lead in the solder. 
The LED's that change colour usually do so by being a pair (or more of LED's in one package, some have one common connection and one for each colour, in which case its just a question of adjusting the current for each element to get the required colour mix, either by simple resistor selection or by doing some pulse width modulation. 
Those that are red/green and just have two connections have two elements, one green, one red, that are connected in reverse parrallel.  This means that if the supply is connected one way, the red element works, reverse it and the green glows.
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Doc

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Re: LED's for lighting
« Reply #9 on: April 21, 2006, 04:48:48 AM »

malcolm,
And if you're really bored, try cutting the 'top' off of a metal cased transistor.  Apply small currents and watch the junction light up...  (Not a joke.  Transistor junctions are basically (sort of) the same as an LED junction and they do light up.  'Course, if you're ~that~ bored, go take a nap.)
 - 'Doc
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Tugger

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Re: LED's for lighting
« Reply #10 on: May 19, 2006, 10:35:51 PM »

Hi

I'm a new kid on the block but I have some info on LEDs for lighting. I have used LEDs on a recent model tug and a lifeboat. As regards brightness, veiwed from the side they are as bright if not brighter than GoW bulbs. The are available to take various voltages. www.maplin.co.uk can supply a range of colours including red and green leds in 3, 6, 12 volts 3mm, 5mm or 8mm. and they start from around 14p each. Coloured LEDs are quite cheap it's the clear ones that are relatively expensive starting at around a ?1.00 each. They can even supply flashing LEDs. I use bulb holders from Mobile marine Models which are machine to take either 3mm GoW or LED or a larger size to take 5mm LEDs. For clear LEDs a resistor needs to be fitted in the circuit to drop the voltage.
if you want further info let me know.
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Re: LED's for lighting
« Reply #11 on: May 20, 2006, 10:22:29 AM »

I have an R.A.F. Crash Tender and it uses L.E.D.'s for lighting. I am using a voltage regulator to keep the voltage at approximatly 3v. This means if your running a motor off the same battery it will reduce the volt drop on the L.E.D.'s so they will remain a constant brightness. Another advantage of this system is that you can add as many lights as you want by linking them in parrallel. For those who may use different voltage batteries you will not notice any difference in brightness as you would with just resistors.

Quote
For clear LEDs a resistor needs to be fitted in the circuit to drop the voltage.

It is not only the clear L.E.D.'s but all L.E.D.'s will need to be dropped in voltage to approximatly 3v.
I have made a webpage up for those who may be interested in building their own voltage regulator.

See:- http://www.modelfireboats.co.nr/ue/byoc/reg.html

Tug

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Re: LED's for lighting
« Reply #12 on: July 15, 2006, 06:43:46 PM »


Just disasembled a birthday card, the one that plays a tune and flashes lights at you,

What a wonderful idea for a disco in the main cabin of the next boat,
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meechingman

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Re: LED's for lighting
« Reply #13 on: July 15, 2006, 10:06:38 PM »

I've just lit my tug with LED's. Used a 5v regulator so I can power them from the 7.2 boat pack or from a 9v battery. I filed down the tops of the LED's, then painted the 'back' and 'sides' of the mast head light, nav lights etc, white, to reflect light back in, then black, to look right. They work well, I have a 'distribution board' that has three fixed resistors and one pot to get the light levels right between amber deck lights, white floods for the towing deck, and the running lights. The Mk II version now being built has four variable pots.l'll also add in some miniature switches for each bank of lights, and add on extra towing and stern lights.

Andy
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Re: LED's for lighting
« Reply #14 on: September 23, 2006, 12:36:26 PM »

I've just lit my tug with LED's. Used a 5v regulator so I can power them from the 7.2 boat pack or from a 9v battery. I filed down the tops of the LED's, then painted the 'back' and 'sides' of the mast head light, nav lights etc, white, to reflect light back in, then black, to look right. They work well, I have a 'distribution board' that has three fixed resistors and one pot to get the light levels right between amber deck lights, white floods for the towing deck, and the running lights. The Mk II version now being built has four variable pots.l'll also add in some miniature switches for each bank of lights, and add on extra towing and stern lights.

Andy

I am about to do something similar.

could you post a circuit diagram, or PM me with details please
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cbr900

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Re: LED's for lighting
« Reply #15 on: September 23, 2006, 04:17:37 PM »

If you need brighter lights use the higher candle power leds, I bought some and they are rated at 18,000 candle power, when turned on through the day they can still be seen even on a bright sunny day.  I also have a battery pack attached under the superstructure so that the lid can come of without disconnecting wires...


Roy
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Subculture

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Re: LED's for lighting
« Reply #16 on: September 23, 2006, 05:28:41 PM »

LED's with a wide viewing angle are available.

For instance, there is the 'Golden Dragon' range of LED's by Osram. These give off high luminance at a 120 degree angle- very close to a conventional tungsten lamp, but much more efficient.

They achieve this by incorporating a built in reflector. However, they are rather expensive and probably a little too bright for most model applications.

Another LED range is the S-flux LED's. These have a radiation pattern of 45 degree, which although less than Golden Dragon, is still much better than most LED's.

These are used on a lot of up market cars (i.e. 3 series BMW) for rear lights, and indicators.

I purchase LED's from these guys-

http://www.lsdiodes.com/shop/index.php?main_page=index&cPath=4

Excellent service, low prices and cheap postage.

Andy

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Re: LED's for lighting
« Reply #17 on: September 24, 2006, 12:41:48 PM »

Maplins' catalogue is a mine of info (especially for the uninitiated) on the use and fitting of electronic components incl. LED's.  Maplins also supply LED covers in clear/red/green/yellow which with a bit of careful masking & painting can become realistic navlight housings if working in a suitable scale. Try www.maplin.co.uk
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Re: LED's for lighting
« Reply #18 on: September 24, 2006, 02:21:59 PM »

With using leds what about if you want to use them as flood lights, any suggestions as what to use for a shade directing the lights onto the deck...


Roy
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BarryM

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Re: LED's for lighting
« Reply #19 on: September 24, 2006, 02:44:22 PM »

Roy,

There's no significant heat output and so you can use whatever you like.
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Re: LED's for lighting
« Reply #20 on: September 24, 2006, 07:07:17 PM »

I'd agree with that, but with a caution.

LED's do give off heat, and the very powerful ones significantly so, to the point of needing some form of heatsink.

However for most modelling purposes, you won't require very powerful LED's, so what Barry says is largely correct.

Andy

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Re: LED's for lighting
« Reply #21 on: September 24, 2006, 07:22:45 PM »

So if you are having down lights you have to make the shade as they are not readily available...



Roy
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Re: LED's for lighting
« Reply #22 on: September 25, 2006, 05:49:38 PM »

I don't understand what you mean by a 'shade'.

Andy

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Re: LED's for lighting
« Reply #23 on: September 25, 2006, 07:56:52 PM »

So if you are having down lights you have to make the shade as they are not readily available...

Roy,]

Assume you mean a decklight housing or similar deflecting light downwards?  As mentioned earlier you can get LED covers which may be modified to become lamp housings. However, given the size of most LED, I would not be surprised if a  light housing sold as a model fitting could not be modified. Just a matter of searching.
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Re: LED's for lighting
« Reply #24 on: September 25, 2006, 08:26:45 PM »



In which part of north London dont they have lamp shades then ? ;D ;D


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