Need SMPS suggestion

Then lamp degradation becomes an issue. Honestly, I've thought about just connecting up a big dummy load and leave the things running overnight. What a waste!

robert

Surely this is a professional problem that needs a professional solution. Just go out and spend money on a collection of system power supplies, such as the Lambda ZUP or Genesys units, and mounting racks. Your descriptions of the job do suggest that they should be able to afford it.

The luxury route would be a ZUP36-12 for each lamp. This gets you full knob-control of each lamp's V, I, and Over-V, with the later option of remote sensing and control, via a daisy-chained RS232/485 comms link.

--
Tony Williams.

You can buy open-frame switching power supplies cheaper than you can make them, particularly at the 150 watt level. Most of them will accomodate adjustment over at least a small range, and they will hold the output DC voltage constant.

If you want AC on the lights, it needn't be switching-frequency AC, just change polarity now and then. I'd separate that aspect from the other part of the problem, and change polarity periodically with a MOSFET H-bridge; it could operate at 60 Hz or even 1 Hz.

On Fri, 16 Dec 2005 20:45:33 +0800, budgie wrote in Msg.

No it won't, but line voltage is pretty constant.

robert

That could mean you're contemplating ( or maybe in your case constipating) using a SMPS. Your description was rambling and devoid of precision, plus you added the theater stuff which was just so much more extraneous bs- I am not aware of a specialized industry for theater inverters.

On Fri, 16 Dec 2005 14:19:39 GMT, Fred Bloggs wrote in Msg.

That's why I wrote

"Regulated SMPS comes to mind as a solution."

Stating the problem, along with some different possible solutions, is neither. Maybe it just was too much text for you.

??? I don't think we are on the same planet here.

Neither am I, which is why my client contemplates a custom solution. Although I don't know what a theater inverter is. Maybe a piece where the actors watch the audience?

robert

No way can you rely on the line when you want 0.3% maximum deviation.

Could be...

They do watch the audience and become quite critical when they're not astute enough to react with applause at just the right moments. There are good audiences and bad audiences.

If you are doing digital post-processing, you could handle it there.

Betting scenes on whether you'll blow a bulb seems like a dangerous wager.

--
Regards,
 Bob Monsen

I wonder why he can't get whatever bulbs they use now for such things. What's the advantage to using bulbs that are so "temperamental"? They should look into how the other pros are doing it. I've seen photofloods with a calibrated color temperature - admittedly, they were only ordinary incandescents, but I'd bet that they didn't vary from one evening to the next morning.

Or some color-balanced fluorescents - they have absolute control over the color either while shooting, with filters; or post-pro, which it turns out is such a PITA that they'd rather get it shot right the first time.

Cheers! Rich

I assume you mean it takes long for the lamps to get hot. You might have to look into alternative lighting then. The exothermic chemical dynamics of Tungsten with the halogen gas makes it typical of these lamps to work this way. They need about 800C for the Tungsten halide to form. You can try using lower wattage lamps but in greater number as these are smaller and hence will take less time to heat up. I use a 20W lamp for reading, no apparent temperature problems here. A heat pump or a slightly higher voltage to accelerate temperature increases is something I wouldn't recommend as these lamps are notorious for blowing up at higher temperatures and can become a fire hazard. I'm not a Video man but something on your cameras like Automatic color control , electronic switching or white filters may work.

theJackal

--
And good players and bad players, and the players\' jobs are not to
criticise the audience, but to bend the audience to accept the
premise of the play and, once that has occurred, to go on with the
bit.

A few years ago I went to a comedy club where a good humored comic
was bombing miserably, even though he had good material, and he knew
it. 

What did he do to save the day?  He summed up the audience as being
able to at least understand shadow puppets and, after satisying them
(us) with various renditions of shadow puppets elicited to push our
silly buttons and get us giggling, he went on with his act.

And he succeeded.  No rancor, no recriminations, no hate.

Just a few laughs, and we all had a good time, and I\'ll never forget
his scrambling around trying to tune in to his audience and his
eventual success.

Kinda like a PLL...

but won't do a damned thing for line regulation .....

Or, use a digital pass to smooth out the lighting. I'm sure this is how the pros do it these days.

-- Regards, Bob Monsen

He was not in a hurry, "hurry" being one human concept he had failed to grok at all. He was sensitively aware of the key importance of correct timing in all acts but with the Martian approach: correct timing was accomplished by waiting. He had noticed, of course, that his human brothers lacked his own fine discrimination of time and often were forced to wait a little faster than a Martian would but he did not hold their innocent awkwardness against them; he simply learned to wait faster himself to cover their lack.

Why repeat *9* times?????????????????

I've yet to see ANY supply authority - or in-house generation system - that can maintain your target 0.3% line regulation. I suspect ignoring that element will later come round and bite you.

"Robert Latest"

** Use 3 x 500 VA transformers, one for each lamp - that way the temp rise ( I squared R loss ) will be only 10% of previous.

Fan cool them as well and there will be almost no temp rise.

If the AC supply varies use a "constant voltage " transformer to stabilise it.

You can also get constant voltage ( ie motorised) variacs.

......... Phil

This thread has got too long to know exactly where to but in, sorry.

Are you sure you are chasing the real problem?

0.3% variation is only 0.3 volts (Approx) at the line input to you studio and if you are getting that good tell us all who you supplier is so we can all get good power. Power lines only offer + or minus 6 or 10 %. so aren't you expecting too much (or too little)? Are you sure the line does not go down as the day progresses?

--
John G

Wot\'s Your Real Problem?

The bulbs are not an issue, the power supply is.

Custom-made.

robert

I've already explained why that's not an option. Fixing stuff in digital post should be reserved for inportant things, not errors that could have been eliminated at the source.

robert