Thursday, March 26, 2015

Cutting the ledstrip

So I bought myself several rgb-ledstrips at the dollar-store (Action) when they had a sale. The strips are 5 meter long on a reel and delivered complete with steering electronics and an infrared remote control. For 16 euro a real bargain. Like I said I bought several and one of them is in my living room at the top of a large bookcase. It was constantly sliding of the bookcase and therefore I designed a ledstripholder with my 3d printer as discussed here.

However that is not what this blog entry is about. I want to use the ledstrip in an infinity mirror. But 5 meter is way to long. So I have to cut part of, it. I really had to test that.

So let us take a closer look.

The ledstrip ended in a black cap.

I was afraid there would be end-resistors or something like that beneath that cap. So I carefully removed it and it then revealed just some contacts nothing more, pfew. 

Now lets look at the strip itself,

As you can see the strip is divided in parts. Each part contains 3 leds, the big white squares. But there is more. Each part contains its own limiting resistors, the small silver dots. So you do not have to take care of that and just supply some power. The strips are connected by copper contacts. And as you can see the RGB leds are common anode types as there is one +12volt lead.

So I took some scissors and cut at the end of the strip one section off.

Now first things first. Test if the remaining part still works.....

So far so good. Now for the testing of the cut off part. I started, using a sharp knife, by scraping of the plastic until the copper contacts were accessible.


Then I attached a 12 volt power supply and.......... nothing happened. So I think I must have cut some wires when cutting away the plastic. So I cut off a new part and this time removed the plastic by melting it with my soldering iron.

Next step is to solder some wires to the contacts and put them into a breadboard. Last week I showed you how to make your own breadboard wires. You can find that article here. That is something that came very helpfull here. 

So now there was only one thing to do: test.

Yep. It works.

For testing I put 12 volts to the lead that marked 12 volts and ground to the other leads. In this picture I just connected one of the RGB leads. The leds are very bright as you can see.

Oh and do not be afraid that you reverse the power, they are leds after all.....

So the lesson learned this time is not to cut away the plastic but melt it away with your soldering iron.

Next stop: steering the strip with power transistors. The end goal is to control the ledstrip with an Attiny or Arduino. The Attiny would be sufficient as it has 5 pins and we need only 3.

Till next time. Have fun.