> My brother once stated that an old computer is still usefull, because > you can put a nice beatifull cloth on it, and use it as a coffee > table. Myself, when I will be given time from other interests, I will > study the problem of how can you control the christmas tree lamps with > an old computer.
been there, done that. use MOC3011's which are a optoisolated triac trigger, connected to appropriately sized power triacs. You can control up to 8 circuits like this with the 8 bits of the parallel printer port with no additional logic. We used to hook up 4 or 8 of these inside of a AC multiple outlet strip, and mount a db25 connector on the side of the power strip... silly little C or basic programs can cycle the bits in various patterns and control 4 or 8 sets of christmas lights. Usually, we'd interleave 4 strings of lights, so cycling 1 of 4 bits thru them creates movie marquis style chase patterns... if you want to get fancier, put a 'PIC' microproccessor in there, and you can use serial IO control and have some 'intelligence' in the ligth controller so the computer doesn't need to be on to run the patterns you've chosen, however this will need a 5V DC power supply to run the PIC. oh, there's a few variants on the MOC30xx chips... there are ones that have integral zero cross detectors can only be used for on/off, however the ones without this circuit can be used as a dimmer if your software times the pulses against the A/C line (you'll need your own zero cross circuit connected to one of the status pins on the LPT port, and some tight realtime software to decide when to trigger the circuit relative to the A/C phase...) ah, datasheet on the Motorola MOC parts... http://support.tandy.com/support_supplies/doc66/66249.pdf you can use the example circuit labeled 'resistive load' for lamps, and control like 15A per string at 115VAC with the appropriate sized triacs (thats a LOT of large christmas lights :D)... Note, if you, like my friend, run 4 strings of 10 amps each, be careful not to turn on more than one at once with your software, or you will likely blow a fuse. Use triacs rated at twice your line voltage and twice your maximum intended current and fuse the whole thing to something less than your line circuit (we used a 12A circuit breaker on an american 15A circuit.) _________________________________________________________________________ Unsubscribe & list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
