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Re: DIY MH?



>Well, I for one would certainly like to hear more on how this was 
>accomplished.
 
I used a 9' 8" piece of Homaco ladder. This is cable management ladder, of
the kind usually used to keep the wiring neat in big data centers. It was
about $90 or so before their bit price increase of 20% or so this year.
It's a steel setup 12" wide with "rungs" every 10" or so that are welded
between the rails. The two hanging brackets were about $50 each and hold
the ladder about 12" below the ceiling (these could be home made from some
aluminum or stainless steel flat stock easily for additional savings).
Since the setup is in my basement, it was easy to mount the brackets to the
floor joists, and I built the stand so that after everything was assembled
the space between the top of the tank and the light fixtures would be what
I wanted - about 12-14" or so. It's an open top tank.

The light fixtures are horizontal reflectors that are cheap knock offs of
the spider light reflectors. They mount to brackets I made from aluminum
extrusions that are mounted to the ladder "track" using UHMW polyethelene
rollers. I use some Coleman Cable cable that I have mentioned on this list
before to wire the fixtures to the remote ballast assembly. The remote
ballast houses three 175 watt ballasts plus igniters, all in an aluminum
chassis from Fair Radio Sales (http://www.fairradio.com) that apparently is
no longer available. There is a fan in there, and I use the circular
plastic connectors I mentioned in a previous post to connect the MH
fixtures to the ballast assembly. The unit uses a standard IEC computer
power cord for power so that I can disconnect all the wiring from it should
I need to move it around.

That's most of it. Someday maybe I'll post some pictures of it somewhere
:-)

> I mean, I love A&H Supply and the PC's I have - but for tanks of 150 gal >and 
>up  I just can't picture a practical way to use them or even a hood of any 
>type for that matter. Too deep. 

You might be surprised. I have found that their larger PC fixtures have a
surprising amount of throw due to the very good reflectors they use.

> Pendant MH, either bell shaped or the other rectangular type, would allow 
>you to stick your arm in the tank whenever you want. I like that idea a >lot.  
>Ascetics aside, not having to build a hood is worth something too, but all 
>this talk about being blinded by these hanging fixtures has me worried.
 
I used smoked acrylic as a shield around the fixture's edges to cut down on
glare. I had thought about aluminum sheet too. Glare is *very* nasty with
an open-frame horizontal fixture like I have been using. There is no option
but to put in place some kind of guard.

>American bulb. Speaking of being cheap, on a six foot tank, I wonder if one 
>could effectively use just two pendants with a larger (and cheaper) 250 >watt 
>MH in each fixture?  Anyone try this set up?

I think the angles would get too extreme to effectivly get the light into
the water column. When you reach the critical angle (can't remember what it
is for water), the light will mostly just bounce off and you'll end up
lighting your ceiling. I don't know if a pair of fixtures would be able to
couple enough light into the tank to be more efficient overall than three
175 watt fixtures would be. At the very least you would have much larger
shadow areas withing the tank. I've never tried it myself though.
 
> Because now that I admit to being "cheap" -- if one were to shop around a 
>bit, I think one could probably find a good, plain old tar ballast and the 
>Iwasaki 6500 bulb somewhere for between $100.00 to $130.00 for both. How >hard 

I get the ballasts for something around $30 or so from a local wholesale
eletrical supply house. The bulbs (6500 K) are somewhere around $60-70 or
so. You also need to include a mogul socket, preferably with the 125C wire
pigtails to make the connections easier. These were around $5/each for me.
I got the reflectors from an online place that I can dig up again if you
are interested. They were in the $30-40 range.

>their pendants really worth an extra 120.00 each? What qualities must a DIY 
>pendant fixture have safety wise and how do you focus the light beam 
>effectively if you tried making one yourself?

Well, safety wise you need to worry mostly about heat. The wire has to be
able to handle the high temperatures, as does the socket and the reflector
itself. The socket is easy, since the heavy ceramic mogul sockets are all
rated for the high temperatures of MH bulbs. I have no idea where to get a
"real" reflector for a vertical pendant, unless you could get a parts-only
deal from one of the regular lighting manufacturers. The wire is easy too,
but you will probably need to order it from a supply house since hardware
stores typically do not have the right cable available for this
application.
 
> I'm a big fan of DIY but I've never done MH. It certainly doesn't look any 
>harder than wiring NO fluorescent, PC or any other project I've attempted, 
>except for the part about coming up with a decent looking/functioning 
>pendant. There must be some alternative to a galvanized bucket. OTHO, if I 
>had some reasonable expectation that a bucket might work, I probably 

It isn't any harder to wire up. Maybe actually easier if you consider that
muliple-lamp flourescent systems can sometimes have a lot of wires to work
with. The biggest concern is to use the correct wire, and a ballast
enclosure that won't melt with the heat. As for a bucket reflector, I don't
think that would work too well. You'd probably have better luck with a
stainless steel mixing bowl since at least those approach a parabolic shape
and tend to be polished inside.

>I've read everything on the Krib site -- is there somewhere I can find more 
>info than this on DIY MH?

Check marine / reef aquarium sites. MH is more common for salt than
freshwater setups IMHO.

     -Bill

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Waveform Technology
UNIX Systems Administrator