mookaloid
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| posted on 8/7/05 at 07:20 PM |
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LED help please
I am helping to build a dolls house for my niece and I would like to install some lighting.
I thought some LED's like this might be good, but I have never used them before and know nothing about them.
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&category=66952&item=7529270534&rd=1
Anyone got any thoughts on this and how would I wire them up? are they like bulbs - do you just apply a voltage and they light up? or do you need some
kind of electronics to go with them?
I thought I might use a battery pack or maybe a transformer.
Any help gratefully received
Cheers
Mark
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JoelP
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| posted on 8/7/05 at 07:32 PM |
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it is simple to wire them up, nothing more than wires, power and switch. I would use one of those circuit boards with copper strips and holes on it
(sorry, dont know the correct name!) and have them placed where required with simple small switches, like the ones stocked in maplins etc.
Not sure of the best power source, i suspect that current will be so low that 2 1.5V rechargables would be ok - certainly safe at least.
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spunky
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| posted on 8/7/05 at 07:48 PM |
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Just like a bulb but must be correct polarity, long leg is +ve
Just kooked at the ebay listing. they would be like like bright spotloghts
John
[Edited on 8/7/05 by spunky]
The reckless man may not live as long......
But the cautious man does not live at all.....
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andyharding
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| posted on 8/7/05 at 07:55 PM |
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LEDs need a current limiting resistor unless there is one built in. If not they might explode!!! and will almost certainly burn out.
Are you a Mac user or a retard?
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mookaloid
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| posted on 8/7/05 at 08:45 PM |
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Thanks Guys
What size resistor would I need Andy? or how do I tell if it has one built in?
Cheers
Mark
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David Jenkins
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| posted on 8/7/05 at 08:54 PM |
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You can get LEDs that are right for set voltages, usually 5v or 12v. If you get them the wrong way round they just don't light up, but no harm
is done. They aren't much more expensive than ordinary ones, and much easier if you're an electronics novice.
Just make sure that you don't cook them when you solder them up - leave a reasonable lead length and hold the wire on the LED side of the joint
with a pair of fine-nose pliers (the electro-nerds will now tell you that the pliers are unnecessary, but they are a good idea for anyone who's
not soldered components before).
Don't be wary of LEDs - they really are easy to deal with.
David
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mookaloid
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| posted on 8/7/05 at 09:25 PM |
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Hi David,
Did you take a peek at the ebay listing above?
would they be 5V?
Cheers
MArk
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andyharding
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| posted on 8/7/05 at 09:39 PM |
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Can't remember how to work it out I'm afraid. From the listing it doesn't look like they have built in resistors. I'm sure an
electronics buff will help you out.........
Are you a Mac user or a retard?
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MikeRJ
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| posted on 8/7/05 at 10:02 PM |
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The resiistance and power rating of the resistor required depends on:
Vsupply i.e. what voltage you run your dolls house on
Vf(led) The forward voltage of the LED. This will be in the LED datasheet but for most ultra-bright whites it's usualy about 4.5v
If(led) The current you want to run the LED at, the higher the brighter, up to the safe limit. 20mA is normaly plenty
R = ( Vsupply - Vf ) / If
e.g. for 12volt supply:
R = (12 - 4.5)/0.020 = 375 Ohms
Power dissipation of resistor:
P = I^2 * R
For the above example
P = 0.020 * 0.020 * 390 = 0.156 Watts
In practice, resistor values come in a standard range, known as E12, E24 or E96 depending on tolerance. The E12 series should be easily obtainable,
and the closest value is 390 Ohms. A 1/4 or 1/3 Watt resistor would be adequate for the power dissipation.
Note that ultra bright LED's are usualy quite directional, unlike the small fillament lamps, so you will probably need to diffuse the light
through e.g. some thin white plastic, tracing paper etc.
[Edited on 8/7/05 by MikeRJ]
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mookaloid
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| posted on 8/7/05 at 10:19 PM |
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Thanks Mike,
That looks really useful
Any thing elase I need to know?
Cheers
Mark
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Jasper
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| posted on 9/7/05 at 11:46 AM |
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Reading this post with interest.
I'm an electronics novice - just about managed to wire up my own car (but glad I don't still own it!).
For the next build I have been thinking about making my own LED rear lights, and possibly shift lights as well (I really like the two lines of rear
leds on the new Suzuki motobike). Anybody know if there a good novice type book or web site that will tell me all I need to know so I can start
experimenting?
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Peteff
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| posted on 9/7/05 at 01:17 PM |
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It's easier to use grain of wheat bulbs, it's what my wife and most dollhouse builders use. You can use copper strip which is available
specially for the job and can be papered over easily or thin copper wire. 12v adaptors are used in different ratings for different amouints of bulbs.
These are my wifes' projects.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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MikeRJ
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| posted on 10/7/05 at 03:05 PM |
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quote:
Originally posted by mookaloid
Thanks Mike,
That looks really useful
Any thing elase I need to know?
Cheers
Mark
The only real way to damage LED's is by too much current, or by putting too high a reverse voltage on them. Most white LED's have a
fairly low reverse breakdown voltage of just 5 volts, so be carefull if you use the LED in a position where the voltage could be reversed. If this is
an issue, a simple silicon rectifer in series with the LED will protect it (e.g. 1N4001 , cheap as chips, easily available).
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