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I want to make a basic Christmas light controller. What should I be aware of? I know the lights can only be strung end to end to a total of 4 strands (in most cases). How much current do the draw? I know the fuses are usually 350mA at 120VAC. How could I control the lights? Triac? Relay? I know triac would proved faster switching and no arcing so I'm guessing thats the way to go. What should I expect in the way of difficulties in doing this? I thinking several slave units that plug directly into mains and then I switch the power to outlets coming from this unit (Read: dissect three way and place controller in between mains and outlet). Whats a safe way to control the units from a distance? My yard is fairly small so control lines would be quite short. I don't think radio is the answer although I don't want to string wires everywhere. How are the commercial units controlled (like the one used by the guy who synced his lights to a song by the Trans Siberian Orchestra, I know it used a computer but was there a physical wire connecting the two items)? I leaning towards actual wire connections between each unit and making use of opto-isolators. Any thoughts or ideas? Please help.

Triacs are always nicer than relays when you can use them.
I dont know exactly what you need help with though, as you seem
to understand what you are doing already.
You know you really need fuses though even if you use relays.

Normally you would measure the current using a meter and size
the fuse a bit higher. For light bulbs you may want to use
slow blow types, but fast blow will probably work too and be better
at protecting everything.

Thanks for the reply. I see now that I have left out the details I was searching answers for. Let me get my thoughts organized and plan out the details as far as I can and I will be back (later tonight). I got theory of operation down (I think) but I need help with part selection, among other things.

i took a controller off of a string of lights a set i found in the dump.
( the ones with a multifunction controller), and i got it to control larger triacs, and wired that into 4 outlets. so now i can control more sets of lights, and they all seem to work together (synchronised) when you have them spread out across the yard..

ya i know its a hakked idea, but hey , its simple and it worked for me
i usually leave the controller in random mode.

This will be all over the place but I'm trying to get everything figured out. I checked into just buying a Christmas light controller pre made to see if it was worth it ($999 ^), I'll stick to homemade or nothing at all. I know how to make the master unit. The master will have a MAX232 for computer to PIC communications. I wanted to add a zero cross circuit to know when to switch on the lights to lower surging. I think I'll be ok putting that part of the circuit on the master board and using the master to trigger the rest. That will save cost and complexity if it works? I know I will use wires to send data from the master to the slave units. I think I will use telephone station wire. It's cheap has many wires and good for distances. I will use optoisolators on all the data connections. How should I hook it up? My control wires would be at max 100ft long. What voltage should I use on the control lines to get good signals at the slave end of things? I can get the data from the other side of the isolators to the PIC for processing and I can handle all the PIC coding. I want to make the lights dimmable using PWM. Will that work ok? I will use one full port of the PIC for light control (8 Bits/pins/outputs). What Triac (or other electronic part) should I use to switch on/off the lights? If I am going to make this I want to do it once and do it right so assume for each of the eight outputs that the load will be three/four strands of lights strung end to end. I have yet to measure and verify this but I hear the max current for this would be 3 amps. What parts can handle this? What should I be aware of? I need to power the slave units somehow. Whats the most cost effective way to do this? I could put a RC voltage divider and a full bridge rectifier within each slave unit or I can use 2 of the 6 wires in the Telephone station wire to provide the power. If I use the telephone wire to power the slave units how do I get a good PIC mcu safe 5v? Zener and a resistor? 7805 and some caps? I hope this isn't asking to much. Thanks.

Look up www.computerchristmas.com, a great free do it yourself christmas light site! Merry Christmas!

Thanks for the link zotdoc but the site seems to be down.

Sorry, short on time this morning so I may have read a bit sloppily.

A few gotchas to keep in mind with TRIACs: Some will not switch on in phases 2 and 4- this will make dimming difficult beyond a certain point. Some (many) do not have isolated tabs- shock hazard.

As for lamp current, measure the cold resistance of a few. This will give you an idea of the inrush current you must allow for.

Signal voltage over telephone wire: 'phones operate on about 50V, and the wire is often rated for 300V. Limit the current.

PWM control shouldn't be too difficult, just delay the signal to the TRIAC.

All this having been said, you should be able to make something better for less than 1/10 the price. Enjoy.

http//computerchristmas.com - I looked at it today and it is up, so retry, lots of great stuff including triac light switche design etc.

zotdoc wrote:Look up www.computerchristmas.com, a great free do it yourself christmas light site! Merry Christmas!

There's an extra ',' in the link. Remove it in the address and you are good.

TOK