DIY 70w Metal Halide Pendant.

[dakar]

Not stupid at all... I'm assuming by the normal bulb you mean the original bulb that was in there, it was a 500w Halogen, way too inneffficient (heat) and the wrong color spectrum for our uses, the halogens burn around 2900K if memory serves me right. The new halide burns at 14000K. I hacked the Halide into the halogen fixture because I didn't want to purchase a fixture and quite frankly, because I could

Cheapest route for halides will almost always be a DIY, magnetic ballasts can be found for cheap, best as far as type and color is a matter of perspective, appearance versus growing power. But that is beyond the scope of this thread.

mb im stupid but why the new ballast and not the normal bulb Im going to add some metal halide to my tank and looking for the best and cheapest way

[Tom McKenna]

No it isn't contnue might one hehe Im thinking of adding metal halide to my tank is why I ask I already have a orbit on it now. WIll halide bulbs work in the halogen fixture without a new ballast?#ed_op#br#ed_cl#

[dakar]

If only it were that easy, all metal halide bulbs require a ballast to fire. The majority of single ended MH bulbs run at 250v, but also require the current to be at a certain frequency, much higher than the standard 60hz than is present at the wall. That's the simplest explanation I can think of at the moment.

[jerryc]

Halogen lamps run of your wall outlet 120 volt without help

MH need a boost to start so you need a ballast to give it a boost
a ballast is just a transformer that runs the voltage up to start the lamp
from your wall outlet

[segraves1]

this is cool......so if I want to put a 250Watt bulb in, it just clips right in?

[dakar]

The 70w and 150w DE bulbs are the same length, however the 250's are a little longer. That doesn't mean that the fixture and lampholder can't be modified to accomidate a 250w bulb.

As a side note I did endup drilling a pattern of holes across the back (now top)of the fiture to allow heat to escape. It was getting pretty warm even with a 70w bulb, anything larger and it would be a 'must do'.

[jerryc]

Some folks are putting in a fan for the larger lamps

[perpetual98]

Dakar, the 150W bulbs are longer than the 70W bulbs. I speak from experience. I thought they were the same too. The 250 are pretty big, and the 400W DE bulbs are rather large.

[dakar]

Ooops... thanks for the correction! Do you have the actual length difference close at hand? I looked at them and they sure looked close, a little extra hacking on the fixture/lampholder would fix that.

[perpetual98]

Here's what I got off of the net...

70W - 4-3/8"
150W - 5-3/8"

Not much luck quickly finding the lengths on the 250 & 400 watt DE bulbs.