Page 1 of 4 123 ... LastLast
Results 1 to 10 of 32

Thread: Cutting LED Light Strands

  1. #1
    Join Date
    Jan 2013
    Location
    Greenfield, Indiana
    Posts
    418
    Post Thanks / Like

    Default Cutting LED Light Strands

    I have a project I am working on with LED C7 Holiday time light strands (I know, not the best quality, but I am just starting out) and I need them to be shorter. Is it possible, or even advisable to cut these to the length I need. I have heard different opinions on the subject.

  2. #2
    Join Date
    Nov 2011
    Location
    Las Vegas, Nevada, U.S.
    Posts
    2,155
    Post Thanks / Like

    Default Re: Cutting LED Light Strands

    Pretty much no. With out re calculating the dropper resistor. There is a few threads about it just use the search.
    "Jack of all trades, master of none,

    Certainly better than a master of one"
    Projects:
    [URL]http://hackaday.io/project/1092-Raptor12-AC-light-controller[/URL]

    Videos
    [URL]http://www.youtube.com/user/KingOfKYA/videos?flow=grid&view=0[/URL]

  3. #3
    Join Date
    Jan 2013
    Location
    Greenfield, Indiana
    Posts
    418
    Post Thanks / Like

    Default Re: Cutting LED Light Strands

    That is what I was afraid. Looks like I will just have to figure out how to put more lights on my project, but that is not a bad thing, just more work.

  4. #4
    Join Date
    Jan 2011
    Posts
    187
    Post Thanks / Like

    Default Re: Cutting LED Light Strands

    If you want to do a little DIY, you can make custom strings using the correct resistors. I have made many, and also convert all cheap store bought strings to full wave. This is what I use to work it all out.
    Attached Files Attached Files
    [url]https://www.facebook.com/pages/Christmas-On-Cleveland-street/284096428308803[/url]

  5. Thanks PCPackrat thanked for this post
    Likes PCPackrat liked this post
  6. #5
    Join Date
    Dec 2012
    Location
    New Jersey, USA
    Posts
    498
    Post Thanks / Like

    Default Re: Cutting LED Light Strands

    What I've done to shorten LED strings (or remove those pesky "fairy light" controllers) is put a resistor and a capacitor in series with the LED string, then flip half the LED's around for full wave, like so:

    AC-led.jpg

    The capacitor (two listed for different AC voltages) blocks current down to about 20ma and you can string easily one LED facing each way or twenty and then some.

    And, it's dimmable too.

  7. #6
    Join Date
    Jan 2013
    Location
    Greenfield, Indiana
    Posts
    418
    Post Thanks / Like

    Default Re: Cutting LED Light Strands

    Quote Originally Posted by frederic View Post
    What I've done to shorten LED strings (or remove those pesky "fairy light" controllers) is put a resistor and a capacitor in series with the LED string, then flip half the LED's around for full wave, like so:

    AC-led.jpg

    The capacitor (two listed for different AC voltages) blocks current down to about 20ma and you can string easily one LED facing each way or twenty and then some.

    And, it's dimmable too.
    I am very new to circuits and really have a very basic understanding. I am trying to teach myself because it is something i am interested. Do you happen to have a picture of the actual string you could share? Probably very basic to most people on this forum, but i dont know much about circuits. I have soldered some circuit boards, like the LOR boards but the instructions are pretty easy to follow and dont explain why you are doing things, but i guess they are not supposed to show that. They are good instructions and easy to follow, but i am the type that wants to know why i am doing something, so i have a better understanding. I can probably look at a schematic and a picture and figure it out, but just looking at a schematic and figuring out what goes where i still have to learn. Sorry if this is very basic, but we all have to learn somewhere and there seems like some very intelligent people on here with this sort of stuff.

  8. #7
    Join Date
    Dec 2012
    Location
    New Jersey, USA
    Posts
    498
    Post Thanks / Like

    Default Re: Cutting LED Light Strands

    Taking a picture of strings I modified won't really give you a visual because they're wrapped and sealed. It will look like a string of christmas lights with an extra wire. Here is what I did in hopefully a simpler description.

    I took some LED's and ran them in series, positive to negative, positive to negative. That is string "A".
    I then took the same amount of LED's and ran them in series, facing the other way. That is string "B".

    I then put string "A" in parallel with string "B", put a 1K resistor on one end, and a .47uf capacitor on the other. I attached 120V "hot" to the capacitor, and 120V "neutral" to the resistor.

    Because the two strings of LED's face in different directions, string "A" lights on the first half of the AC wave, and string "B" lights on the second half of the AC wave.

    The resistor and capacitor limit the current to about 20ma, which is what most LED's seem to like.

    If you want to run on 220-240V instead of 120V, replace the .47uf capacitor with a .22uf capacitor.

  9. #8
    Join Date
    Jan 2013
    Location
    Greenfield, Indiana
    Posts
    418
    Post Thanks / Like

    Default Re: Cutting LED Light Strands

    That does help quite alot. I am running 120v. Doing this type of DIY has always interested me, but it is pretty tough to just think of things to make in order to learn. The Christmas light show DIY, there is a reason and many projects that can be done in order to learn. I have had no formal education on electronics, and no one in my family has ever done anything with electronics, so this is all really new to me.

    With the resistor put in, can you cut down, say a 25 string of lights down to 20 or so? Thanks for all the help, I am learning a lot, and it is very interesting to me.

  10. #9
    Join Date
    Dec 2011
    Location
    corpus christi texas
    Posts
    110
    Post Thanks / Like

    Default Re: Cutting LED Light Strands

    yes you can cut led strings down to whatever length you need. As stated, you must change the current limiting resister to match. You can find led calculators to determine the propper resister but too many different voltages for different leds.
    If you are handy with a multimeter, it is really simple. I cut the string i am going to shorten and place my multimeter, set on milliamps, in series with the wire i just cut, plug it in,measure and record the current (i use DC scale). unplug lights. I then reduce the string to the size I want and put a 50k ohm potentiometer in series with meter and lights. turn pot to highest resistance and plug lights in. slowly turn pot till milliamps match the reading recorded earlier. unplug, remove pot from the circuit, set multimeter to ohms scale and measure the resistance of the pot. this is the ohms of the resister you need. Select the next highest standard resister and solder it in series of your newly shortened string.

  11. Thanks PCPackrat thanked for this post
    Likes PCPackrat liked this post
  12. #10
    Join Date
    Dec 2010
    Location
    Madison, Mississippi
    Posts
    883
    Post Thanks / Like

    Default Re: Cutting LED Light Strands

    This is the way i figured out my light strands also. i have a spreadsheet that i have made with of over 15 diferent brands and all different colors. The colors and forward voltages are mostly consistant. i just know nlw that resistors taks so many ohms per bulb and size appropriately. I sized mine at 3 watts and for rectified voltage.
    Quote Originally Posted by rogelizo View Post
    yes you can cut led strings down to whatever length you need. As stated, you must change the current limiting resister to match. You can find led calculators to determine the propper resister but too many different voltages for different leds.
    If you are handy with a multimeter, it is really simple. I cut the string i am going to shorten and place my multimeter, set on milliamps, in series with the wire i just cut, plug it in,measure and record the current (i use DC scale). unplug lights. I then reduce the string to the size I want and put a 50k ohm potentiometer in series with meter and lights. turn pot to highest resistance and plug lights in. slowly turn pot till milliamps match the reading recorded earlier. unplug, remove pot from the circuit, set multimeter to ohms scale and measure the resistance of the pot. this is the ohms of the resister you need. Select the next highest standard resister and solder it in series of your newly shortened string.
    Last edited by duramadmax; 01-09-2013 at 10:25 PM.
    2017 - Hmmmm...lots has changed...
    Facebook: [URL="https://www.facebook.com/Stevensfamilylightshow/"]Stevensfamilylightshow[/URL]
    Youtube: [URL="http://www.youtube.com/channel/UCodTAksQo4tgLAyabUe1-dg"]Stevens Family Light Show[/URL]
    Web: [URL="http://www.stevenslightshow.com"]http://www.stevenslightshow.com[/URL] (under construction)
    [img]http://sig.falconchristmas.com/18222[/img]

Page 1 of 4 123 ... LastLast

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •