50% duty cycle limited 240v Controller

Discussion in 'LOR 240V AC' started by deonb, Jan 4, 2015.

  1. deonb

    deonb New Elf

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    I posted this on another site, but someone suggested I repost here, because there's more experience on this forum with 240V equipment.

    I want a "50% duty cycle limited, 240v Renard"!
    But why??

    So I can run 110V lights directly off a Renard in a 240v environment
    Uh. Why not just run 240V lights?

    Because 110V is a quarter of the price of 240v lights, so I can have more of them! It also opens more options.
    So just get a 240V/110V transformer...

    The math doesn't work out. Will spend way more in transformer capacity than lights.
    Why not just output only 50% in Vixen?

    It's difficult for things like Nutcracker, so eventually I will make a mistake and burn out a bunch of lights. I want a value of 255 to always mean 127 at the hardware level.
    Pretty sure this whole idea won't work...

    Well, it works conceptually using Light-o-Rama controllers - I can run 110V lights for long times, just need to duty-cycle limit them manually. I have no hope of getting a automatic hardware solution running on LOR though. Hence the look at Renard.


    So what are my options here?

    Unfortunately I've never Renard'ed before - so far all my AC stuff is LOR controllers. But it always requires going through physical wiring hoops in my setup to make the 110V lights work - generally by wiring 2 strings or substrings in series. Works great, but takes time.

    Series-wiring outlets or extension cords makes things easier, but doesn't work well for arches (ends up with too many lights per segment). So I would prefer if I can just do this at the controller side - by simply halving all duty cycle values given to it by Vixen and friends.

    One snag... I may want e.g. 12 Renard output channels on 50% duty cycle limited and 12 channels on 100% duty. (Mix of 110v and 240v).

    Here is what I considered so far:

    * Have a board in front of the Renard board (on the RS485 inbound side) that takes Renard (or DMX) input and halves all the input values as they come by. I can have jumpers (or something) on it to specify 110v/240v on a per channel basis. Elegant, but lots of work. But it will actually work on LOR boards as well, which is a plus.

    * Modify something like a E1.31 bridge to output half values. I think though a E1.31 bridge is closed sourced firmware. Is there an open source firmware equivalent?

    * Modify the Renard firmware itself. Similar to the E1.31 bridge, but I prefer leaving the Renard firmware alone and have it be updatable.

    * Use a special Vixen controller plugin type to limit the duty cycle. Danger Will Robertson - someone is going to screw this up the next year and use a wrong controller setup, and it will seem to work until the lights go out. If going that way, I would still want to pair it with a Renard firmware update so that I can at least tell the Renard - "Hey, I'm using the right plugin and values - ok to listen to me". (e.g. use a non-existing output with a magic value (42 of course) that tells Renard - everything is A-OK). However, if I do that, then I may as well just update the Renard firware to do the halving to start of with.

    * Use different SSR's for the 110v outputs. That would be nice, but I think this doesn't work. You have to duty-cycle limit things at the logic level.


    I want it to be fool proof, but it doesn't necessarily have to be perfect. Sending 240V full duty to a 110V incandescent or LED string generally doesn't have disastrous consequences. It shortens the span of the lights (significantly so - but if you accidentally do this for a few seconds, it's actually not a problem). So if it sends out 240V for a few cycles during bootup due to some output that doesn't have a pull-down, I can live with that.
     
  2. David_AVD

    David_AVD Good news, everyone!

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    ACL tends to be a low voltage forum. Most people are moving away from 240V lights here.

    As for the general idea of limiting the output to 50% to get your 110V, I'll just say that that I don't think it's a good idea at all.
     
  3. lithgowlights

    lithgowlights Senior Elf

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    With AC Lights the way a renard works is it turns on the light a period into the waveform, both on the upper and lower half of the cycle. 50% in vixen will delay turnon of the Triac until roughly half way through the waveform. Now for AC the peak voltage is actually half way through the waveform, and for 240V lights that peak is just under 340V.

    Add to that the first time you turn on the lights the r4esistance is pretty low, and increases as the filament heats up (Ever notice lamps rarely blow except for when they are first turned on?) How long do you think your 110V lights will last being put across 340V peak?

    My guess is not long at all - maybe a few half cycles!

    My personal view is iof you have no experience in the electrical industry, don't understand AC, then don't play with 240V - it will kill you, and has the potential to kill others! I am also very much against 110V lights in the yard as well, as look at how many people complain their 110V lights trip their GFI/ELCB/RCD devices - one is simply too many!
     
  4. AAH

    AAH I love blinky lights :) Community Project Designer

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    I have told a number of people at the Adelaide and Melbourne minis that it is cheaper to throw away any mains voltage lights that they have and start again with low voltage dc lights. A LOR AC controller is something like $16 per channel. A DC controller can be had from $2 per channel. That leaves you with $14 for a set of lights.
    I'm assuming that you are in Aus or UK based on the 240V supply. The insulation requirement for 240V lights is so much more stringent than for 110V as it's so much more likely to kill you. If you have a look on the 110VAC Xmas forums you will see all sorts of posts about people tripping earth leakage (ground fault) circuit breakers. Their solutions are to isolate the metalwork of their mini trees etc from the ground and therefore leave them "live" and unsafe.
    There is a reason that the 240V lights are more expensive and a fair portion of that has to do with keeping people safe.
     
  5. battle79

    battle79 Full Time Elf

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    As Lithgow said, the logic here is flawed, 50% duty cycle still sends out 240Vrms (340Vpeak) just for shorter periods. You will get roughly half the watts that is true, but you will still have high voltages.

    You still have 240V in your yard, only now the lights are not built to 240V standards, instead they are likely to have insulation failures and could be extremely dangerous.

    As AAH said, as sad as it seems, DC lights are the best option in all cases and usually end up cheaper in the long run due to controller cost being much cheaper.

    Regards,
    Rowan
     
  6. OP
    OP
    deonb

    deonb New Elf

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    I can see that! Sorry. I'll go away. I see everybody is very hesitant about running line voltage on here.


    Things may be different in Australia, but virtually all 240V lights I've ever seen in my area, are using identical lightbulbs, identical wiring gauges and identical insulation from their 110V counterparts - very obviously made in China by the same manufacturers.

    The only difference is the number of bulbs per segment, whether it be 2x50 (110V) or 1x100 (220V).

    So they're not more expensive because they're safer. They're more expensive because there is less buying power behind them.
     
  7. David_AVD

    David_AVD Good news, everyone!

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    No need to go away. Just pointing out that ACL is not the best forum to ask that specific question.

    Hopefully there's plenty of other things you'll find here that will interest you. :)
     

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