LED strips - with single LED tear capability?

[gavino200]

Most LED strips seem to be set up where you can tear the strip every third LED. I'm looking for a strip that can be torn after every LED so I can cut a strip to any number of LEDs. 

Anyone know what such a strip would be called - ie how I would search for one?

 

[cteno4]

I’ve only seen the single color leds in 5v strips that have a resistor for each led (so you can cut at 1x incrmeants). I’ve seen 12v singles that are RBG that are singles.

 

https://www.ebay.com/itm/D748-led-strip-2835-DC5V-waterproof-flexible-tape-light-60leds-rope-stripe-1-5m/312346791284?hash=item48b951cd74%3Am%3AmjEGYOftStpAq4JSgQYIO1A&LH_BIN=1

 

since you had about 2.3k resistance on the 3 led units you were effectively running each led at 0.5ma. 

 

with the 5v if you want to run say 6 at your like 0.5ma like the others you would be pumping 3ma (they are in parallel now). So your big dimmer resistor would be 8.7 / .003 = 2900 then less the 100 or so on the strip already so about 2.8k.

 

you are running the leds some in parallel here (actually you are in the 3 led strips, just two strips of 3 in parallel) off the dimmer resistor to drop the voltage and current, but if leds matched well it should be fine and since total amperage is way below the 20ma rating of each led you won’t have a run away, but some may end up being brighter than others or at worse one way out of spec and it sucks up all the current.

 

jeff

[gavino200]

With the ones I have, if you cut any one of the three, all three go off. There’s a complicated circuit path. It’s too delicate to repair once cut.

[chadbag]

You probably could buy a 5V string and use it with with 12V as long as you put in your extra resistors etc.  That would allow you to use individual LEDs from the strip.

[gavino200]

This one is RGB I believe. 

[chadbag]

8 minutes ago, gavino200 said:

This one is RGB I believe. 

 

Which one?   You can buy white and warm white in 5V with what look like individually accessible LEDs

 

 

[cteno4]

The one I linked are regular single color leds. RGB (sorry dyslexia makes me call them Ginsburg as I was calling the movie RGB to folks half the time and they would look at me funny). You can tell the rgb ones as they have 4 connector pads at the breaks instead of 2. The only rgb ones with 2 or 3 pad (usually 3) connectors are the fancy ones that have the addressable control chip with each led to set the rgb levels from a power bus to do all the fancy chasing lights (they use a control signal for the chip to drive rgb led on each module separate).

 

jeff

[gavino200]

5 hours ago, cteno4 said:

The one I linked are regular single color leds. RGB (sorry dyslexia makes me call them Ginsburg as I was calling the movie RGB to folks half the time and they would look at me funny). You can tell the rgb ones as they have 4 connector pads at the breaks instead of 2. The only rgb ones with 2 or 3 pad (usually 3) connectors are the fancy ones that have the addressable control chip with each led to set the rgb levels from a power bus to do all the fancy chasing lights (they use a control signal for the chip to drive rgb led on each module separate).

 

jeff

 

Thanks. I just saw the second picture was blue and assumed variable color. 

 

Actually it would be fairly easy just to solder out the resistors and replace with either a blob of solder or a tiny piece of wire. Then all I'd need would be a single limiting resistor and I could use them for any voltage. 

 

How did you find those btw? What search words did you use?

Edited March 4, 2019 by gavino200

[gavino200]

I ordered a meter of white and warm white. The jackpot would be something like this with 0805 LEDs

[cteno4]

why do that? just the same using the dimmer resistor to limit the input current to the strip. i guess there would be the concern that the individual led resistor tolerances would also add an additional variable in there, but again as total current is way below the tolerance of a single led it should never be an issue. 

 

both ways of having the individual resistors or not is still a parallel wiring of leds that can have the led tolerance issue so problem still there.

 

if you want to just do straight parallel led strip and a single dimming resistor then it would be way easier to just solder 1210 lets between two buss wires.

 

or if you want it perfect then it would be just removing the individual resistors that run the leds at like 20ma and replacing each with a resistor that runs the led at your desired brightness (like 2.2k). but that requires replacing a butt load of 0603 or 0805 sized resistors! but thats just as hard as removing all the resistors and jumping them, just jump them with a new resistor.

 

might dig around on ebay and aliexpress as there are a gazillion on ebay!

 

jeff

[gavino200]

48 minutes ago, cteno4 said:

why do that?

 

Only if the resistors happened to be too high for a 3.3V supply

 

48 minutes ago, cteno4 said:

 

if you want to just do straight parallel led strip and a single dimming resistor then it would be way easier to just solder 1210 lets between two buss wires.

 

I like that they're flexible and self adhesing. It makes for an easy install. But I promised you I'd give the bus wire a try. There's some in the mail.

 

 

48 minutes ago, cteno4 said:

 

might dig around on ebay and aliexpress as there are a gazillion on ebay!

 

 

I already looked at about a third of a gazillion and didn't find any. But now that I know they exist I feel heartened for further searching.

[cteno4]

2 hours ago, gavino200 said:

Only if the resistors happened to be too high for a 3.3V supply

 

Ahh no mention of 3.3v! Actually I’m guessing it may limit it just right to down to a 0.5-1ma

 

you can also use thin brass rod of you want it stiffer, but it’s more expensive. I found a 26g floral wire that soldered well and was like $2 for a bundle of 30 or so 1’ pieces. Stiffer than buss wire.

 

jeff