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Posted by Peter Olsen (205.191.171.239) on February 05, 2001 at 17:43:49:
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?
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?
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.
Does anyone know of the controllers I am talking about and/or know how to modify them as per the above? I am also intrigued as to how they operate, given that they work on 24v AC, but there is no obvious rectification or regulation in the circuit in front of the IC chip.
Please reply to: polsen at ar.com.au (You know what I mean. I don't want to insert the @ and invite spam.)