I have most of my parts in and am ready to do some wiring but before I do I need a few questions answered.

First I was planning on doing this with an external ballast and one power cord going to the projector.

wire 1 - Ballast out common wire (white) and LCD + Fan (return wire)
wire 2 - ballast out current (red) Whatever ballast voltage is
wire 3 - LCD + Fan (current) 120V

Is this a proven method and is 14 gauge wire sufficient or is 12 needed?


After turning the projector off, I want a timer that wont allow you to turn the projector back on during the bulb restrike time. Also during this time I would like the fan to run to cool the projector. This will bypass needing a thermal switch.

1: What is the restrike time of the S400DD?
2: Is there a cheap (<$20) way to implement this timer I described? (length of timer being the answer to question 1)
3: And out of curiousity... what is the output voltage/amperage of a S51 coil and core ballast?

Thanks

Edit: Just thought of another question. What is good enough for a VGA cable. I will need a 15ft or 25 ft and I have seen a huge variety in prices which makes me think there is a big variety in quality. Is this sufficient? 25' foot vga cable
And yet one more question. Does it hurt the bulb by trying to turn it back on before the restrike time has passed?

1. When you say external ballast, I assume that it will still be within the projector box. (The consequences of a ballast being separate from the projector do not bear consideration!)
2. Your AC power should come into the box, go to a fuse, and from there a distribution block. From the distribution block (Or terminal strips) you should be able to run power to anything that needs it. The ballast, fans, LCD power supply, PC power supply, 12V adapter for fans, or whatever.
3. Your restrike timer isn't so hard, as long as you're willing to put the parts together. You'll need a power supply, (The one you run your fan from should be adequate, if it's a 12V spply) a timer IC, (A 555 would be an excellent example) and a one-shot timer circuit. There are many examples of these available on the 'net. Your restrike time will vary with ambient temperature somewhat. For the actual restrike time data, start looking for manufacturer's data.
4. VGA cables can be shielded or ushielded. For a projector, I'd recommend shielded, first because small degradation of signal will be magnified (literally!) and second because of the real possibility of magentic interference from the ballast. Moderately priced cable will do very well, and only if you still have a lot of interference problems would I consider going to the "high end" (Or high priced, more like) cables.

Supraguy,

Please expand on your thoughts of an external ballast. What implications would you have from an externally mounted ballast? I don't see anything wrong with this as long as you protect it from being touched.

Thanks.

Sam

Yeah. I was planning on having the ballast in a seperate box on the floor and then ceiling mounting my projector. What is the matter with that? Joe did it on the bakery pj.
Also I have looked at ushio's site for restrike times on the S400DD and havent had any luck. Does it hurt the bulb if you try to turn it on too soon?

Well, for starters, it's inefficient. The ballast takes your wall voltage and takes it to very high levels. The wire betwene the ballast and the socket has a resistance. It's small, but it's there. The more the resistance, the greater the amount of power gets dissipated (wasted) by the wire. In general, the longer the wire, the greater the resistance.

This also does hold true for the household wiring, but since the voltage is lower, the losses are lower. Also, wasted wall power (though annoying) doesn't have an effect on the light output. There is much higher wattage available from the wall than there is from the ballast. Losses from the wall can be made up by just drawing more, but the ballast is rated to provide the amount of power needed, not (necessarily) more.

I'm also personally uncomfortable with having high voltage lines hanging around, especially around things which can be sensitive to EM interference. (My audio amplifiers come to mind.)

Seeing these things used in industrual lighting applications, I note that the ballast is generally in the fixture, even though the fixture is hanging from a ceiling, making this an inconvenient place to put them. It COULD be mounted centrally, but isn't. My thinking there is that electrical engineers who get paid a lot of money to design those things may well have a reason. (And I know a few EEs, so I might just ask. )

About what voltage are these ballasts outputing?

~400 I believe

I recommend using ballast remote is the way to go for HPS 400W ballast you can set your ballast 50' from PJ maximum. check link for specs.

http://www.sperolighting.com/ballast.html

Thanks for the link. It also states the output voltage is only 175-225 for the S51.

This is actually the opposite of how it works. Line loss is REDUCED when transformed to higher voltage. This is why the power company transmits power along its grid at a high voltage (10 of thousands of volts) and lower amperage. Then close to your house it will pass through a transformer and be stepped down to lower voltage with increased amperage.

You will lose much less power to heat with high voltage low amp, than low voltage high amp.

Because the ballast is transforming the power to higher voltage the effect of wiring is reduced, and should be negligible.

Maximumshow is correct with losses. I'd go with 12 guage wiring. You can get some excellent VGA extensions here. Thank Agent707 for the source of VGA extensions.

Is there a need to lockout the switch that turns on the projector during the restrike time of the bulb? Or is it fine just to wait about 5 min, and try to turn it on, and if it doesnt work try again in a couple minutes.

Dergrin,

If you are going to use S400DD with eballast I don't know if you can run with 3 wire setup but for coil Joe, did on his PJ If you are doubt about the setup you can get info from a electrician if ballast common wire will create any issues on your 120v circuit.

S400DD restrike time- This is very tricky if you are using S51 coil 95% of the time Lights on fist strike for eballest its kind of 70% of the time strikes first time if fails on first time had to strike 2-3 times to start the lamp. I also noticed if the lamp was switched on and off within 4-5 hours when you switch on the PJ again with eballest lamp lights on first strike.

I dont know if this is when your lamp getting old or lamp need to be worm a bit for 100% first time strike. but definitely coil is better for striking compare to eballast.

I have a coil ballast to clear up any confusion.

No harm trying to restrke except you loose your lamp life span and you are not going to light your lamp until lamp cool down.

Only harm in MH lamps is if you use wrong Ballast this can even blow the lamp if you use a HPS ballast for a MH lamp.

Be careful of the High Voltage (>2KV) from the ballast to the lamp.
Make sure wiring is well insulated, and wire run is out of way of traffic areas.

I decided to put the ballast in the box.

Nisus,

To my understanding from the link posted above these ballasts only output 225V.


Skanmyth,

I am using the S400DD bulb which is a conversion bulb. It requires the S51 HPS Ballast

Peak Voltage necessary for starting will be High pressure sodium 150-1000 watts: 4000 volts!

OPEN CIRCUIT OUTPUT VOLTAGE of ballast, besides peak of starting High pressure sodium 150-400 watts, most models: 220 volts RMS AC