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Fast, Quick, Cheap, Good looking LED room lighting (for anyone)

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Welcome all :-) This is my first instructable so comments are welcome :-)

What i hope to show you is how to make quick LED lighting that is on a TINY buget.

What you need :

Cable
LEDs
Resistors (510Ohms for 12V)
Stapels
Soldering iron
Cutters and other basics
Hammer and a nail!

(NOTES FOR n00bs)

LEDs need about 30 milli amps (0.03 Amps) or they burn out
To work out your resiance use:

V=IR

Voltage (V) = 12
Amperage (I) = 0.03 (30*10-3)
Resitance (R) = ?

SO :

V/I=R

12/0.03=400Ohms
or more...
i used 510 so my LEDs arent running at the brightest they could be

 
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Step 1: Costs

Picture of Costs
Costs:

Cable : 8.51GBP high grade white cable per 50m ($13.99)

LEDs: 6.18GBP (Cheaper by the 1000) (the LEDs i used are 13,000 and 6,000 mcd with a angel of 25 degrees)

Resistors x100: for 0.99GBP

Staples: Well cheap...

Which works out at:
0.89 per metre!

Spacing of 1 LED per 10cm is enough (get the spacing right or it looks strange)

which isnt bad for really nice lightening that on average the leds will last 11+ Years!

I used a power adapter i had lying about but anything that is 12V and lying about will do fine :-)
Just as a general rule you need 30mA per LED. (this isnt strictly true, but it will keep you within tolerences)

so if you had 20 leds you need (30*10-3)*20=600mA or 0.6 A

Step 2: Cable up the room

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Quick and easy you need to run 2 cables and make sure you dont cross them over at any point or itll get messy

Seen in the picture is what your cableing should look like all the way around the room (or where ever you want the LEDs)

Great guide, looks nice. Very simple, practical, flexible, and easy to understand instructions. Good luck in your future projects, this first effort is a success.
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mellink (author)  QuackMasterDan3 years ago
love the look well done, and thanks :-)
NikonDork3 years ago
 Great 'ible! I have a few rooms wired with a few LED's for mood/low level lighting. 

Ive been saving these babies from the trash at work for over a month and now I have over 30 feet of em. I think im gonna see if I can find some decent sized crown molding and go around my whole living room.
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Are those surface mounted leds? Is there someplace you can buy the flat mounted and ready to go?

Cheers!
Amazon
you can get them in any color or RGB with several types of silicone coating for $5-6/ft or even un-coated ones for just over $4/ft
Yes, they are surface mount warm white LEDs mounted to a thin, flexible PCB strip with the resistors already mounted. The circuit board is lightly coated with a varnish and is water resistant. Normally it comes in rolls, and can be cut at designated cut marks. It runs on 12v, no matter the length. You can order a roll of them (In colors too) on the internet. Just google "LED strip lighting"
You could always send some my way :)
Heh, I have a whole box of them now! I think im saving most of them to go around my porch's railing for some nice low level lighting at night. Meanwhile im finding handy places around the house to put a few. I just finished refinishing my bathroom's medicine cabinet. It was old and rusty looking inside. After all the sanding and priming and painting, I figured what the hell, a few strips inside with a tiny reed switch mounted to the door would be pretty sweet. What do you think?
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mellink (author)  NikonDork3 years ago
like it :-)
Where do you work that they are throwing these things out?
I work for a company that builds arcade redemption games, the kind you win tickets from.
meissler4 years ago
I'm a bit confused with the resistors here. Everything is in series, right? So you have a 12V battery, and let's say (just for a clear example) 10 LEDs that can have 1.5V across each. Why do you need a resistor, and why one resistor for each LED? Isn't the voltage across each LED going to be the same without a resistor or am I wrong? Thanks.
Each LED will be receiving 12V when they are wired in parallel. So each LED will need its own resistor in order to work with the higher voltage. It is important to note that the more LEDs that you use the more power they will draw from the battery.
oh crap it is in parallel cause of the 2 cables, didn't put that together. I'm a little confused about the cables though. You use 2 of them: one end of each of them gets hooked up to +/- of the power adapter, but what about the other ends of each wire?
they are left untouched and seald possibly with tape, if they were connected it would just create a short.
Hycro junits153 years ago
I would just stick a female plug on the end, just to make it a little neater in appearance, plus, you could connect another string, assuming your power supply is capable of it.
Actually , you could connect 3 (3.3V) LED's .
that would give you 12 - 9.9V = 2.1 V ( Instead , of a resistor , connect a smaller LED ) (and a small amount of resistance , usually )
It can be seen on http://www.LEDCalc.com/
What i did for my room lightning was 2 LEDs and 1 130 & 120 Ohm Resistor ( I Wanted more brightness , since it's my room , and i could replace led's quickly )
In each line .
Because it's 9V and 350ma From my wall-wart , i placed 17 lines of LED's , (34 LED's )
mellink (author)  Electronics Blurred1 year ago
You could indeed, but I wanted a larger spred and this method allowed for it to be neat :-)

I have the 12V coming from a PC PSU.
edwin9941 year ago
Oh my~
Impressive .....
how long did you take for doing this?
mellink (author)  edwin9941 year ago
A couple of hours :-) It's really really easy!!!
gaby1st2 years ago
I don't understand if the average of the led's affect the voltage rating like 12v and if I need a transformer to prevent that.
mellink (author)  gaby1st1 year ago
Please could you rephrase the question :-)
Sky_line914 years ago
can someone just really quick explain what type of cable to use b/c that threw me off a little bit. please and thank you
mellink (author)  Sky_line911 year ago
It's just really standard single core cable. Hope that helps
Hi there,
you can use any copper cable.
I like Your heli :D
FallenSub4 years ago
Hey, how about putting one of those omh trimmer on the power supply (on 12 volts cable), so you can dim your lights!?
Won't work. Sorry. It's a good idea on the first view - use a variable resistor, so you can regulate what current flows. But... what the series resistor actually does is reducing the voltage across the LED. It does so by converting electrical energy into thermal energy - simply said, they get hot. The amount of energy they can convert ('burn') depends on the size. Those in the picture are (I'm guessing here) around 1/4 to 1/2 W. Trimmers and their posh cousins potentiometers are normally rated around a 1/10 W or less as they normally only are used to provide reference voltages in electronic circuits and will burn out in some seconds. (Of course there are high current, wire wound potentiometers, but they come with a cost) So, if you want to dim the LEDs, either use a variable voltage supply or use a trimmer to control a variable voltage/current source, e.g. using the good old LM317 regulator. There should be some nice applications to be found on the net.
How about connecting them in parallel then? =/
Like this (MS paint ftw XD )
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Sorry, physics is against you. (At least as long as your variable resistor is none of this high power wire wound type)
Let's do some calculations:
Some assumptions first:
- the power supply is regulated 9V and can deliver enough current to drive all the LEDs without reducing the voltage due to overload.
- the LEDs are white with a forward voltage of 3.4V at 30mA. (you will have to check the data sheet for your specific LED or measure it)
Let's calculate the series resistor for each LED at full brightness (30mA current, the variable resistor is 0)
The series resistor has to 'eat' the voltage that can't be handled by the LED.
This voltage is 9V-3.4V = 5.6V
Now what resistor will produce 5.6V at 30mA (0.03A)?
Ohm's law to the rescue:
R=U/I 5.6V / 0.03A = 186.6...Ohm -> a standard 180Ohm resistor will work nicely (of by 3% but that doesn't matter at all).
And how much power will it dissipate?
P=U*I 5.6V * 0.03A = 0.186W -> a small, cheap 1/4W type will do.

Now for the case that you dim the LED to half the current - 15mA?
The forward voltage of the LED will drop a little, maybe to 3.3V
The combination of series resistor and variable resistor will now have to eat the difference voltage of 9V-3.3V = 5.7V
How much voltage will the series resistor get?
U=I*R 15mA*180Ohm = 2.7V (since it handled 5.6V, it can do with 2.7 easily)
So, the variable resistor has to burn the remaining 5.7V-2.7V=3V, and that at 15mA.
R=U/I 3V / 0.015A = 200Ohm
And for the power:
P=U*I 3V * 0.015A = 0.045W

So, yes, for a single LED or a few LEDs, you might go with a trimmer, just do the math.

But still.... It can have some nasty side effects.
Trimmers are not designed to be turned under load.
The wiper might lose contact or have less contact while being turned, so it might burn into the resistance.
If you get a higher power potentiometer (say 2W) and decide to use it up to the limit - the poti will have to dissipate (burn) this power. Now 2W is not much, but the poti will not have any heat spreader and get warm / hot.

Just save yourself the trouble and build a current source circuit. E.g. with the LM317 i mentioned - see http://users.telenet.be/davshomepage/current-source.htm as an example - I have nothing to do with this guy, it was the first Google result for 'constant current source LM317'. The current can be made variable by replacing the R with a trimmer - no power problem here, since the load current is not flowing through the trimmer.
You can put the LM317 on a heat spreader and the circuit is immune to changes in the supply voltage (in a certain range).
You might be right , or not .
You can use a 5k pot , if you aren't running too many LED's .
5k is sufficient not to blackout at the other end of it .
And not too powerful to induce a loss at 0 .
Woah, you really took your time to explain some things :D Thanks for the reply man! Very helpful! ;)
you could just keep it simple and dim the 12v transformer using a standard mains dimmer....... 240v/110v-mains---dimmer---transformer---12v-leds i think that would be the best way without making this EASY and CHEAP project COMPLICATED and EXPENSIVE :)
That would probably destroy your transformer or the dimmer. The transformer might die through harmonics that increase the heat generation or the dimmer could die from voltage spikes from the transformer/inductor.
admitedly the effect would not be as good but it would still have some effect
I think the effect should be (with a mains dimmer, a real transformer and a bridge rectifier) as good as a secondary side dimming . There might be a flicker at 100Hz (Europe) resp. 120Hz (US) but that shouldn't be a problem.
Yes, that would be another method. But make sure, that the mains dimmer can handle inductive loads (the transformer) - not all can. A dimmer designed for a 12V halogen system with a reals transformer for said system would do nicely. And make sure, that your power supply has a real transformator (i.e. is heavy). Those tiny switching power supplies (small and light-weight) often don't work with a mains dimmer. That is, because they expect a smooth sine wave and what leaves a dimmer is not a sine wave any more (except for the 100% position). And they normally have a regulated output, so they will try to make up for the decreasing input voltage - no net effect in dimming.
srilyk verence4 years ago
AFAIK (Someone please correct if I'm wrong!) you could use a 555 timer et. al to build a PWM, and control that to alter the intensity of your light. There's something to that effect talked about with the Arduino though I've never done it. I don't know if this would shorten the life of the LEDs or not, though. But with this type of application, replacement should be pretty easy.
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