Tutorial: How to wire up a LED strip.

[Tealc]

This tutorial covers wiring up any old LED strip to your computer's power supply in a number of ways, but also to an independent power supply for use outside your case or on the back of your monitor or something else.

First of all if you can't be bothered with all this faffing about with bits of wire, connectors and the potential to damage your power supply or PC then you should really be looking at OcUKs extensive range of LED strips, which come with modular connectors that can be connected together to create full case lighting.

http://www.overclockers.co.uk/productlist.php?groupid=701&catid=1428&subid=1430&rows=0

Anything you decide to do with LED strips from this guide is your responsibility. I accept no responsibility for anything you do so don't even think of blaming me for something you've done wrong. None of the voltages inside a PC case (PSU excluded) can actually hurt you.

Things you will need:-

1) Some sort of mating half for a PSU or motherboard connector. eg Molex, fan connector.
2) A soldering iron, and some flux cored solder
3) Heatshrink
4) Something to cut and strip with. A pair of wire cutters, knife or scissors will do.

If you don't have a soldering iron or heatshrink then you can twist wires together and cover them with insulation tape in a colour of your choice. It's not a permanent solution and may come undone at some stage but it's better than nothing.


So what is a LED strip anyway?

A LED strip is a string of small Light Emitting Diodes, usually surface mounted onto a long thin strip of flexible plastic material. The LEDs themselves are semi-conductors that produce coloured light when a current flows through them. LEDs are one way devices, meaning that if you wire it up wrong nothing happens as current can only flow in onhe direction. If you wire it back to front it won't blow your PSU or motherboard, it'll just not work, which is a good thing I suppose if you fear for your components.

Here are a few different types of LED strip.

RGB 60 per metre

RGB 30 per metre

Some waterproof flexible one

And the cheapest type. 15 SMD per 30cm and waterproof. The LEDs are tiny little things but do produce some decent light.

Here is one lighting up a plate drawer, the spread of light is quite uniform and fills a lot of the space.

Unlike the official LED strips from the likes of Bitfenix the cheaper strips will often come without connectors and just have two bared ends. The problem here is how on earth do we get this connected up to our PC to give it the light giving voltage and current any LED needs?

There are a number of ways you can do this.

Use a molex extender, splitter thing.

Use an old fan cable and connector...

..use whatever this thing is..

..or this..

..even the connector of a long since binned Tri-cool would do the job.

So basically we can hack and chop up a Molex or a fan connector. Everyone has either a Molex or a fan connector available, if not here's one..

http://www.overclockers.co.uk/showproduct.php?prodid=CB-012-AK&groupid=1929&catid=153&subcat=

First up I hacked a Molex to Molex fan adapter cable, like the first pictured above and the one linked to for sale.

First off we need to cut the fan connector off

Then, strip the wires and tin them if you are using a soldering iron. Put some heatshrink on the wires here if you have any. The red wire will be your +12v wire and the black will be the 0v, or ground, or -ve if you prefer.

Some LED strips will come with two same colour wires, or maybe one will have a stripe. The one with the stripe will probably be your 'Red', usually anyway. If you wish to test polarity wire up your bared ends to a 9v PP3 battery. The terminals are marked + and - so you can easily work out which wire needs to go to the Yellow or Red on your Molex and which needs to go the black.

Now basically join the red and black wires together using the soldering iron, or if you dont have one just twist the wires together.

So you end up with something like this

The good thing about this method is that if you have two strips you can easily shove another Molex into the free end of the first and daisy chain them.


Next up we have the fan connector. Here's one I cut off a Xilence 80mm fan which I never used.

Same drill, strip the wires and tin them.

Bung some heatshrink on. I usually forget to do this and have to resolder but that's just the fun of doing stuff.

Same drill as before. Join red to red and black to black. Remove the yellow wire as much as possible.

So eventually once you shrink down the heatshrink it looks a bit like this.

And connect it up..

More to come....

 

[Tealc]

And for the next part I will show you how I have my internal lighting power sorted.

For this I use a Molex to Molex fan adapter.

and a mains terminal block. I only had a 3 way and 1 way available....

...but actually use an 8 way in my PC.

We need to remove one of the Molex connectors.

This nearest one is the one we want to keep, the other won't be needed so chop it off.

Here's one I chopped earlier.

We only need the Yellow (+12v) and Black (0v)

Strip back the wires and join some other wires on. I had some 1.0mm Red and Black wires kicking about so used that. I didn't use much, maybe 100mm but you can use more.

Also cut off a little bit about 40mm long and strip both sides.

..and arrange like this.

Now anything you screw into the leftmost 2 slots will be grounds and the rightmost will be +12v. Very handy if you want to wire up several LED strips, cathodes or any other device that you want. The most I've had one mine is 2 LED strips, 3 of my modded LED fans and also my illuminated front panel.

Here's the one I made just powering two strips on the bench.

Now this is interesting. A switch. One thing that I sometimes like to do is switch off my LEDs. Because I have a central distribution point for my lights I can easily switch them all on or off using a single switch.

What you need to do is break the Red (or Black) wire and solder it across the switch. What happens is that when I throw the switch the circuit is created and current can flow. When I flick it off the circuit is broken.

You can run this switch to wherever you want. All you need do is extend the broken red wire to wherever you want it.

and finally how to wire them up to an external power source. This is actually quite simple.

Here's a power source. This one isn't 12v but will be adequate to show how this works.

Cut off the DC barrel type jack somewhere near the end (but not too close so it can't be used on a future project).

Take your LED strip bare wires and solder them to the DC adaptor. You might want to test it before soldering up as it's not always easy to tell polarity. If it lights up then go for solder, if it doesn't swap the wires aorund. It's only low voltage so it won't hurt you.

And here it us working.

AC adaptors like this tend to throw out higher voltage at low current draw so even though this is only labelled as 4.5v it may well be giving 8v or thereabouts with only 50-100mA draw.

A proper regulated DC power supply would be recommended for this sort of light use but I probably wouldn't bother and just grab a £2 or £3 '12v 1A' plug in power supply like you can get on eBay.

 

[Tealc]

could I wire a regular dc led strip to usb?

You could wire it up yes. However it wouldn't work too well as LEDs need a certain voltage to illuminate and the amount of light they would generate at just 5v would either be nothing or very little, depending on the colour of your LEDs.

The majority of LED strips are 12v as they are used on cars as well as PCs. I couldn't find any for 5v use, or at least not like the other strips you can buy.

 

[Tealc]

Thank you, Very nice!
What about the RGB LED strips?
Do they wireup the same way?

No they don't unfortunately. I only included them as images to show the different appearance. With those that I pictured I also have an RGB PWM controller box, which varies the colour of each of the red green and blue LEDs that make up the leds. Dealing with three circuits rather than just one really does make them a lot more complicated.

Still when you get the RGB strip you usually get everything you need including remote and PWM box, maybe even the PSU.

 

[Tealc]

External PSU in the RGB lighting kit is what puts me off!
If you could do a tutorial on wiring RGB lighting kit which has a control box and remote to the internal PC PSU would be appreciated!

That's simplicity itself. Get a molex to molex connector extension, remove female molex (that's the one the same as on the PSU), remove red and black wires (we don't need 5v), strip yellow and black wires and solder to a relevant sized DC barrel type jack that the control box requires. The only thing you have to watch out for is polarity of the DC jack, most things need +ve to the centre and -ve to the barrel. In fact my control box even has a little picture to tell me which way around the voltage should be.

DC jacks can be bought on eBay and the Molex to Molex can be bought here on OcUK.

10 minutes is all it would take, once you have the parts anyway.

 

[Tealc]

I've updated Post #2 with two new methods.

Ahh ok
I was more concerned about the required current/voltage mismatching!

Provided you use the correct colour PSU wires they should always be an expected voltage. Yellow = 12v, Red = 5v, Orange = 3.3v and Black = 0v

As for current you could have a 1000 Amp power supply and it would happily run a 200 milliamp RGB LED strip. The device pulls what it needs from the power source. Current flow is never a push type of arrangement. The Molex will supply enough current for several metres of RGB LED strip, even when R G and B are at full intensity.

 

[Tealc]

Nice. I hope you don't accidentally plug a 5v USB device into that 12v powered USB connector at any stage as it won't go well.

I might be inclined to fill that light gap in the middle as you mention.

 

[Tealc]

Hey Tealc, great tutorial.

Currently modding a couple of strips to go in my case, I've been testing them hooked up to my fan controller and it's worked perfectly. I've wired them up to 3pins and they plug directly in and are adjustable, only thing is since there is no yellow wire the fan controller LED doesn't light. Is there a way I can 'fake' the connection for the yellow wire so it see's the 'fan' speed as maximum (Therefor showing a red light).

Thanks.

I've never really looked at what exactly the tach feedback signal looks like in any depth, beyond that it occurs twice per revolution and will either be pulled up by the fan controller to 12v or work at whatever the fan is working at.

I suspect the easiest way would be to throw 12v into the tach signal or alternately if it does need a square wave (on/off) signal then a simple 555 timer IC circuit would make it work.

 

[Tealc]

You could always use a resistor as a jumper. Something like a 10k should drop any current down to just a milliamp, which won't damage anything. I doubt if it's break anything but without knowing exactly how the tach is received by circuit it's just guesswork.

You could also try feeding in the PWM signal from your motherboard. That seems to work ok.

 

[Tealc]

That looks like a 1W 470 ohm 2% resistor there, although it could be a 2W. I'm not really able to tell the wattage just by looking at them as I don't have enough experience with resistors other than 1/4W.

The transistor could be anything. Loads of transistors come in that metal package.

The motherboard header is only 5v on the 4th pin PWM output, the others are 0v, 12v and tach. I would expect that board to be 12v powered, given that it has a 470 ohm resistor, which is a good resistor value for pretty much any single LED you'd want to attach to it.

It's likely that the circuit is a 8 pin microcontroller.

 

[Tealc]

There aren't enough components visible on the board for it to be a 555 timer circuit. I suppose there could be stuff on the other side though.

Sorry I'm not really in a position to be making circuits at the moment as I'm moving house in a few days.

 

[Tealc]

Ah yes nice little controller. £4 is silly money. You couldn't even buy a microcontroller yourself and make it that cheap.

 

[Tealc]

Even sillier price.