Results 1 to 7 of 7

Thread: shorten LED strings

  1. #1
    Join Date
    Nov 2009
    Location
    Edgewood, KY (Cincinnati Area)
    Posts
    724
    Post Thanks / Like

    Default shorten LED strings

    I have some LED shortener boards I bought a while back and I never could really wrap my head around using them. I finally have a good project to use them on to shorten some left over 50 count warm white full wave LEDs from 50 to 25. I need to drop it really to 20 but I figure half would be easier and just tape over the extra lights.

    Is there a guide on figuring out what resistors I need to use in the board to shorten the string like that? I can't get a good grasp on it from what I've read so far.

    Thank you,

    Jason

  2. #2
    Join Date
    Jan 2010
    Location
    Omaha, NE
    Posts
    1,811
    Post Thanks / Like

    Default Re: shorten LED strings

    Look at the string and if there is a spot where there is only 2 wires between the led lights you can cut the string there and add a plug on it.
    Doug

    Having Fun with Wire Frames and Lights.

    www.wireframedlites.com
    Custom Hand Made In USA

    FaceBook:
    http://www.facebook.com/wireframedlites

    Phillips Family Display
    http://www.facebook.com/phillipsfamilydisplay

  3. Thanks JasonPortwood thanked for this post
  4. #3
    Join Date
    Dec 2014
    Location
    Springville, Utah
    Posts
    461
    Post Thanks / Like

    Default Re: shorten LED strings

    Quote Originally Posted by Dougp View Post
    Look at the string and if there is a spot where there is only 2 wires between the led lights you can cut the string there and add a plug on it.
    You usually can't cut full-wave apart like that.

    For 50 ct string comprised of 2 25ct sections, there will be three "blobs". Each new section requires two such 'blobs'.

    This can be done, but you have to cut one section with two blobs, and then on the other section - that only has on blob - you have to complete the bridge with a couple diodes and usually a resistor.

    I posted a full-wave circuit diagram awhile back - that helps make it clear.

    Jimboha

    As for shortening the segments from 25 to 20: typically for white LEDs you can substitute one 220 ohm 1/4 watt resistor per LED. If you do all of your strings the same, then they will dim the same as each other, though perhaps just a little differently from an un-modified string.
    Last edited by jimboha; 05-09-2018 at 02:48 PM.
    Springville, Utah

  5. Thanks JasonPortwood thanked for this post
  6. #4
    Join Date
    Nov 2009
    Location
    Edgewood, KY (Cincinnati Area)
    Posts
    724
    Post Thanks / Like

    Default Re: shorten LED strings

    Thank you both for the replies. It makes a lot more sense now. I'll look up the diagram.

    Jason

  7. #5
    Join Date
    Jan 2016
    Location
    Lizella, GA
    Posts
    1,102
    Post Thanks / Like

    Default Re: shorten LED strings

    Quote Originally Posted by jimboha View Post
    You usually can't cut full-wave apart like that.

    For 50 ct string comprised of 2 25ct sections, there will be three "blobs". Each new section requires two such 'blobs'.

    This can be done, but you have to cut one section with two blobs, and then on the other section - that only has on blob - you have to compete the ridge with a couple diodes and usually a resistor.

    I posted a full-wave circuit diagram awhile back - that helps make it clear.

    Jimboha

    As for shortening the segments from 25 to 20: typically for white LEDs you can substitute one 220 ohm 1/4 watt resistor per LED. If you do all of them the same, then they will dim the same as each other, though perhaps just a little differently from an un-modified string.
    Actually my cheap Wal-Mart 100 & 70 count LED strings that I have gotten the last couple of years don't have any blobs, they have 2 or 3 sections (depending on the color) where you can just cut the 2 wires and add a plug.
    Matt

  8. Likes Dougp liked this post
  9. #6
    Join Date
    Dec 2014
    Location
    Springville, Utah
    Posts
    461
    Post Thanks / Like

    Default Re: shorten LED strings

    Quote Originally Posted by Ruppro View Post
    Actually my cheap Wal-Mart 100 & 70 count LED strings that I have gotten the last couple of years don't have any blobs, they have 2 or 3 sections (depending on the color) where you can just cut the 2 wires and add a plug.
    Are they full-wave?

    The half-wave Walmart LEDs I use do have over-sized sockets on each segment. That socket that has a plug cap with resistor inside.

    With those strings you can do exactly what you said. But the OP said he had full-wave strings.

    Jimboha
    Springville, Utah

  10. #7
    Join Date
    Dec 2014
    Location
    Springville, Utah
    Posts
    461
    Post Thanks / Like

    Default Re: shorten LED strings

    Quote Originally Posted by jimboha View Post
    I posted a full-wave circuit diagram awhile back - that helps make it clear.
    I found them right here in this forum:

    http://doityourselfchristmas.com/for...400#post410400

    Jimboha
    Springville, Utah

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
  •