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Posted by a person who is a moron (193.193.32.13) on February 09, 2001 at 01:33:45:
In Reply to: Re: Transformers in parallel and xmas light controllers posted by Tomi Engdahl on February 06, 2001 at 05:03:19:
: : I am seeking help on 2 topics relating to Christmas fairy lights.
: : 1. Transformers in parallel.
: : The xmas lights run off 240v-24v AC transformers (I'm in Australia). I have a long run from the transformers to multiple sets of lights so I want to connect up the outputs of lots of transformers in parallel, then run a single thick cable, then branch off to the
individual sets of lights. I can ensure that all transformers are in phase, but I am concerned about what happens if some are slightly higher voltage than others. Will the higher voltage ones "push" the current in reverse through the lower voltage ones and burn them out?
: Youe expectations are right. He highest voltage
: transformer will try to push current to
: lower voltage transformers. How much this happens
: depends on transformer output impedances and
: voltage tolerances. For cheap christams light
: transformers this might be problematic.
: For many christmas lights on one power supply
: I would say that replacing those many small
: transformers with one larger ones would be
: less problematic solution. Replace many small
: 24V transformers with larger one which has at
: least the power of those small transformers
: (what your lights take). If your transformer
: does you will need does not output more
: than few ampleres of current, just connecting
: the lights in parallel to the other end
: of the thick ehiugh cable shoudl do the job.
: If the transformer is very high power, then
: I would recommend adding fuses to those
: separate outputs for safety (many amperes
: in short circuit could easily heat up thin wire
: in one light series with bad results...)
: : One solution I thought of was to connect each to a bridge rectifier, giving half-wave output, then connect all the outputs together, thus isolating each from the other. But that is lots of diodes to connect up. Do I need to worry, or is there a simpler method of isolating them?
: Bridge rectifier isolates those transformers so
: that they do not try to push each other.
: What this bridge rectifier does not do is
: to evenly balance the load to those transformers,
: so the highest voltage transformers will take
: most of the job in powering those lights,
: so they might overheat with disasterous results
: (think what happens when they fail the next ones
: take all the load and fail..).
: : 2. Flashing controllers.
: : There seems to be a standard flashing controller on most sets of flashing lights here. It has 8 different settings (eg. Combination, twinkle, slow-glo, slow-fade, flash, hard on etc.) and has 5 wires coming out, a common plus a wire to each of 4 different coloured circuits in the string. I've pulled a couple of different brands apart and the circuits appear to be almost identical.
: : Most have some crude (capacitor?) memory function, so they remember which of the 8 settings they were last on even after being powered off. My problem is the memory either doesn't work at all, or doesn't last from one evening until the next. I want to hack into the circuit and hard-wire it onto one of the 8 settings. (no. 2) so they come on to the same setting every night. Alternatively I want to insert a bigger capacitor to extend the memory retention.
: I haven't hacked with those built-in controllers
: and I don't own any light with one. I can't
: help you on this topic. If anyone knows good
: web documents on this, feel free to tell about
: them here and I will add the links to them to
: www.epanorama.net
: : Please reply to: polsen at ar.com.au (You know what I mean. I don't want to insert the @ and invite spam.)
: I also send this answer to your e-mail box.
just buy some from a place called a "shop" if you have been (ever) out of your home you may know what one is wow look its a blue sky. we;lcome to the real world bloody idiot