# LED Tape / NO CUT MARKS!



## danhuman (Dec 19, 2016)

I joined up to ask this question as I've not been able to find and answer anywhere online and have nobody to ask IRL regarding this. Closest thing was another unanswered thread on here.

So I've had a nightmare with setting up some LED mood lighting and blew one cheap set up for stupid reasons. I bought a new 5 metre RGB LED tape with seperate transformer and remote unit etc from a reputable trade firm. 

On getting the pack home and opening it up, the tape not only has NO cut marks where you'd expect, but also no copper terminals along the tape. Just LEDs and resistors. 

Is there any way I can cut this tape or are these ones not meant to be cut? There is a solder joint at regular intervals along the strip, but not the thin copper plates that you usually cut through on these. I have the old blown tape to compare it to and the placements of LEDs and resistors is the same, just no copper. 







I can still return this product but I'd ideally like to fit this before xmas!! 

Big up x


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## Lithopsian (Dec 19, 2016)

A picture would help enormously. Or a link to where you bought it that shows the tape. Is this 12V? 5V? You can almost certainly cut at the solder points, visible copper or not, but it would be good to see the tape and get a fuller answer for you.


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## danhuman (Dec 19, 2016)

Thanks for your reply, I did include a picture but as I am a new member perhaps it isn't showing up?

I'll give you a direct link to the picture in my dropbox if that helps here:

https://www.dropbox.com/s/zkc1gkloob29szc/IMG_5488.JPG?dl=0

It's a 12v system. I bought it from ScrewFix in the UK:

http://www.screwfix.com/p/led-cabin...tracking url&gclid=CI6CkZ3JgNECFQ48Gwod5NQE3A


The only company details are SFD and on looking them up it appears to be in Thailand which gives me some cause for concern. They don't seem to be as well built as some I've seen but I paid my money down and I have a project to finish!

Thanks dude
The final termination at the other end is on one of the solder joints so I figured that if I cut back the resin coating and desoldered the joint at the position close to where I wanted it would probably be ok.


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## Lithopsian (Dec 19, 2016)

Never seen that before! It is a standard PCB layout (only 30 LEDs/m, low power) but no visible indication of the cut mark. There will be a place where you can cut it, but if you miss you may botch three of the LEDs. Try holding the strip against a very strong light (like itself!) and examine the copper tracks - it should be obvious where they are running back and forwards to go to the LEDs, and where they are running straight to get to the next set of LEDs. You can cut there. It will be in the big gap between two groups of three LEDs and resistors. Or you may be able to see the tracks just by peeling the back off the sticky tape, even by peering very closely at the shape of the plastic tape surface.

Obviously, you can cut at the solder blobs. That's where two separate strips have been joined. You can even unsolder them if you're really handy with an iron. Maybe they don't plan on you cutting these strips. It is a pain to get to the resin or silicone off anyway to make a new connection.


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## DIWdiver (Dec 19, 2016)

I read the Q&A on the website, and one answer says you can't cut them, another says you can cut them but not re-join them. As Lithopsian points out, certainly you could cut at the solder blobs, and maybe you could solder wires on to the cut ends. If you're just looking to cut them, the pattern is easy to identify, and repeats every three LEDs. Pretty likely you can cut them halfway between any two LEDs where there's no resistor, which is where the solder blobs are.


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## DIWdiver (Dec 19, 2016)

By the way, if you use Dropbox and want the picture to appear in your post, click on Insert Image, then when it asks for your URL, you have to edit the one that Dropbox gives you, so it looks like this:

https://dl.dropboxusercontent.com/s/j1fntskjh0atgkh/fullbody.jpg

instead of the original

https://www.dropbox.com/s/j1fntskjh0atgkh/fullbody.jpg


And the image needs to be no bigger than 800x800 pixels.


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## Lithopsian (Dec 20, 2016)

Yes, rejoining might be difficult. Even putting wires or a connector widget onto a cut piece might be difficult. But the actual cutting shouldn't be a problem. You might be able to scrape away some of the plastic covering (after you've scraped away the waterproofing!) and expose the copper underneath, but overall it does seem like they weren't planning on much chopping and joining.

There really isn't much to be scared off with this LED tape. Most strips have a +ve (+12V) rail on one edge and a -ve (0V) rail along the other edge. The RGB 5050 strips have *three* +ve rails, one each for R G and B. So that's the four connections exposed at each end. There are many little circuits running between these four rails, each containing a network of tracks joining up three SMDs and three resistors. There are some pictures where you can see this (https://www.flexfireleds.com/pages/Comparison-between-3528-LEDs-and-5050-LEDs.html). The important thing to note is that in between each of the complicated circuits, the same four tracks will always line up to feed the next circuit. These are the cutpoints, whether they are marked or not

Cutting in the wrong place will usually destroy that particular circuit of three LEDs, but the rest of the strip will still work, although you may need to power it from the other end. You can always cut off any damaged portions to a proper point between circuits. Don't cut it while the lights are on since you will inevitably short-circuit and the power supply may not be happy. You may even burn out part of the tape wiring if the power supply doesn't give up first.


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