This style of LED string used to be quite expensive, but it’s clear that it lends itself to mass production well as the price has come crashing down quickly. This type of LED string has two lacquered copper wires with surface mount LEDs soldered in parallel along their length. The wires are obviously held tightly in parallel and formed into a flat topped peak that has the lacquer ground off. The wires seem to be pressed tightly against the back of a surface mount LED, soldered and then dipped in resin that encapsulates the LED and wires for strength and insulation. These may prove to be quite good for outdoor use as the connections are fully encapsulated in resin.
I was intrigued by a set of 100 LEDs designed for 12V, and wanted to see how they were wired. They have been divided into four sections of 25 parallel LEDs that are then connected in series to give a combined forward voltage of 12V (4 x 3V). I couldn’t find a series resistor, so they are relying on the combined forward voltage and the knee/slope that gallium nitride LEDs have where they will have a forward voltage that typically varies between about 2.5 and 3.4V depending on the current passing through them.
The way the sections were hooked in series was clever. Both wires of the parallel circuit being cut, and one sections positive being connected to the others negative and the other wires just folded back and covered with heatshrink sleeve.
