Christmas Tree LED Mystery

The bulbs are wired in parallel...

....or in groups, combination series and parallel....

http://www.resistorguide.com/resistor-for-led/

amps = volts * watts

"amps = volts * watts" ???

Also I'd be wary of any site that sugested putting 30 mA through a standard LED: most are rated at 20 mA. Unless you want them to be a bit brighter for a very short life.

Noted - I will limit any calculations to currents of 20mA max.

Yeah, good catch Randall...

Amps * Volts = Watts

GA. My thoughts exactly. Current source power supplies are becoming the preferred solution for many LED illumination applications for exactly the reasons you describe.

I believe you're right, if you have an "intelligent controller", it makes sense to drive it with constant current. LED brightness is proportional to current whereas the forward voltage drop is a function of color, because the photon energy increases as wavelength gets shorter. Blue lights require more voltage than yellow or red. White LEDs are usually blue LEDs with a phosphor that absorbs blue and emits yellow, creating a mixed color (blue + yellow) of white.

If strings are driven with constant voltage, strings with a predominance of red would be brighter than those with more blue and white.

The fact that the schematic mentions nine strings and the fact that each LED can be either white or colored indicate that there must be some additional electronics there, most probably one control module per string (controlled somehow by the small control module you mention). Each string can be composed of parallel sets of LED's (either 6 sets of 10 or 5 sets of 12 or even (but less probably) 4 sets of 15) and the string's control module can include either series resistors for each set or a constant current supply.

Just to clarify, there are not separate white and colored lamps. Each lamp is capable of emitting white light, or light of one (of four) color. The glass "shells" are all transparent, so no way to know the color until voltage is applied. I played around with one spare lamp and discovered that one polarity equals white light, and reversing the polarity equals that lamp's assigned color. From this I assume that there are two LED's in the lamp, and they are "wired" so that when the "wrong" polarity is applied (via the control module) only the diode matching that polarity lights up (the other - being a diode - does not illuminate since the polarity is opposite) - hope that makes sense.

There is another possibility where the leds actually contain their own current limited power controller. I have a set of leds on my Xmas tree which cycle through all the rainbow colours when fed form 6V to 24V supply and they do all the controlling themselves and have their own current limiting circuit. They look no different to a normal 5mm led, maybe a bit longer but not much.

Not sure if my tree is similar. It appears that all of the "programming" is via an in-line control module, which produces cycling options of white, white flashing, color, color flashing, white/color alternating, etc. and is controlled via an integral momentary push-button, or a remote.

I have rewired store bought led strings in the past although they were just one color. They didn't have a power supply but they were clearly wired as a combination of series and parallel to achieve the desired voltage across the bulbs. They also included a current limiting resistor or two.

I would agree with what others have stated that this tree is either a combination of series and parallel and or the supply is a constant current type.

Also I have found that at least with the multi color strings I was using not all colors of led's were created equal in terms of voltage and current requirements. This difference is generally not an issue if you replace one or two bulbs. If you tried to move all one color together however some parts were very dim or very bright.

Most of the led's I use now are the full color type which have three wires between bulbs. Two wires are DC + and - that is carried in parallel and the third is a data line that allows control of each bulb individually. They use the WS2811 chip type protocol to communicate.

The reason I posted this in the first place is that the top section (3rd of 3) of my tree started having intermittent flickering (distinctive from the pre-programmed on-off flashing) of only a portion of its 120 LED's. I was trying to diagnose the problem by replacing individual lamps in the flickering portion, but eventually just gave up. Anyway, the tree has a 3-year warranty and the company has agreed to send me a replacement top section. Many thanks to all of you who have weighed in. I'm hopeful that once I've digested all of this, I will have a better understanding of my tree's system.