# So those 12v auto led rope led strips - how they wired?



## irksomeremnant (Dec 5, 2011)

Just wondering!

For example, like this...

http://www.ebay.co.uk/itm/2x120cm-1...28?pt=UK_Motorcycle_Parts&hash=item19cb705170

Since they're rated for 12V...how are the arranging all the leds to get the right combination of current and forward volatge....do they simply use one smd resistor per led? Or are they all in paralell with one large resistor dropping the excess voltage - do they use a string of leds with a shared series resistor etc etc...

Any ideas?


----------



## Ken_McE (Dec 5, 2011)

With the 12 volt 5050 SMD strips, and the 12 volt LED rope lights, they have a string of three LEDs and a resistor, then another string of three LEDs, etc, etc. If any one component fails you get three dead lights, but the rest of the string continues.


----------



## irksomeremnant (Dec 11, 2011)

Thanks....so essentially, there's two rails 0v & 12V running the whole lengh of the led rope, with every 3 leds being a 'string' between 12V & 0V.


----------



## bshanahan14rulz (Dec 12, 2011)

yes, they simply parallel 3-LED strings. 
If you are looking to design a series-parallel array, this might be of interest to you: http://led.linear1.org/led.wiz


----------



## alpg88 (Dec 12, 2011)

Ken_McE said:


> With the 12 volt 5050 SMD strips, and the 12 volt LED rope lights, they have a string of three LEDs and a resistor, then another string of three LEDs, etc, etc. If any one component fails you get three dead lights, but the rest of the string continues.



yep, the "power lines", go all the lenght uninterrupted, clisters of 3 leds are wired in series with resistor. you can cut the strip, or add more, 
i sew led strips to my dog's harness, power comes from 6xaaa cells, at 9v leds are still very bright, but not as bright as with 12v, exactly what i needed, since i only need to see them not illuminate anything.
I had cluster of 3 leds fail, i cut the cluster out and replaced with working cluster. normaly power is soldered to one end, but my experience tought me that sometimes main lines brake, and half of the strip is off, so now i hooked power on both sides for redundacy, if your strip is stationary that it not needed, but if it is not and is bent all the time, it helps.


----------

