This is copied from another site, its good info....
HID Ballast Wiring
One of the best ways to save a bundle on equipment is to wire up
your own lights from a kit. By buying the parts unassembled, you
can probably construct a light for half of what it costs you at a
hydro shop. As well, you can avoid the paranoia involved in
shopping there. But I can understand that many of you might be
reluctant to work with wires and electricity. That is certainly
understandable. But it isn't nearly as difficult as you might think.
Let's take a second to examine what is inside a ballast. There really isn't much, especially depending on which type of light you buy. A HPS ballast consists of 3 parts: The transformer, the capacitor and the igniter. A metal halide generally has just the transformer and capacitor.
Every single one of these parts is available at pretty much any lighting or electrical supply warehouse, including the bulb and socket. Break out the phone book and look in the yellow pages under "lighting". Call them and ask if they carry "Transformer, capacitor, igniter (if for HPS), and socket" for whatever size (150, 400, 1000, etc) and type (Metal halide or High pressure sodium) light you wish to purchase. Odds are, they will have it. If not, try another store until you find the one which has what you want. You can also order this stuff from many online electrical supply places. There is virtually no worry about having this stuff shipped to your house, since it did not come from a "high profile" hydro shop.
When you get to the store, you are going to ask for the ballast components, a socket and bulb in whatever size and type you want. The person working there will probably ask you what voltage you need. This is important because the ballast has to be made to run on the voltage at your house. Most houses in the US are wired for 120 volts. So that is the rating you need for your parts. If your house happens to have a different voltage (say, 210) then you need the corresponding ballast parts. Find out if your house has a voltage different than 120
before you get to the store. Another option is to purchase what is known as a "multi-tap" ballast. This type has a special wire inside which you move around and attach in one spot or another depending on the voltage of your house. Some stores may only carry multi-tap ballasts to save money on stock. No matter. A multi-tap ballast will work fine in any situation. Multi-tap ballasts usually have the following options inside: 120/208/240 and 277 volts.
Besides the Transformer, igniter, capacitor, bulb and socket, you are going to also need the following:
About 20 feet of 14 (or better) gauge wire
A "male" plug set
About 8 "wire nuts"
The wire and the plug are for installing the power cord and socket to your ballast. You can also simply buy a long heavy duty extension cord, which you will then cut up. Whatever wire you buy, make sure it is rated to at least 15 amps and 1500 watts (14 gauge). That size is good for wiring all the way up to 1000W lights.
Now, when you get your parts, you will also likely get a
wiring diagram. It may come on a separate sheet of paper, but more than likely it will be on a label on the transformer. Let's take a look at a wiring diagram. I have added a few descriptions for the sake of clarity, but the basic schematic is the same. This is for a HPS lamp and describes the wiring for the 3 internal components and the socket.
http://www.onlinepot.org/grow/_derived/wiringlights.htm_txt_wiring.gif
Kind of confusing eh? Well, that's why I'm here.
Let's take a look at the same thing but in "real time" instead of as a diagram:
http://www.onlinepot.org/grow/_derived/wiringlights.htm_txt_guts.gif
Now, does this make a little more sense? I know it may still be confusing, but take some time to sort it out.
You can clearly see all of the components you will be dealing with and how they will be wired together. Let's take a sec to examine some of the more important points.
If you look at the transformer, you can see it is labeled as having a "short side" and a "long side". These are my descriptions for the 2 different areas of the transformer. If you look carefully you will see that the transformer has two protuberances where wires come out. One of them is thicker than the other. That is the "long side". It is important to know the difference when you go to wire it up.
The capacitor is a simple affair with just 2 wires.
The igniter has 3 wires.
Look closely at the wires running from the socket. You can see that each of them comes to a
junction with two other wires. All 3 wires at a junction (and at all junction points for all wires) are held together with a "wire nut". This is just a plastic cap which screws onto wires to hold them together. Use only wire nuts for connections. Don't use tape of any kind.
Although you can't see it, all wires have something printed on them so you can identify them. It is going to be something numerical ("X1", "120") or alphabetical ("lamp", "com") In my example, wires are noted with X1 or X2 or X3, other ballast kits may have wires which simply say "one" or "two" and "volts" (instead of "120"). Sometimes wires are colored (the igniter wires in my example are red blue and white) sometimes not. When wiring a ballast, don't get mislead by the color of wires on the igniter, capacitor or transformer. These wires are connected according to what is written on them, not by color. Color will come into play when dealing with the wires coming from your power cord and socket. These are going to simply be black, white and green with no labeling.
If you already own a ballast of some kind, go ahead and drag it over and open it up. Take a good look inside. Can you figure out what is going on based on the pictures here? How about based on the internal wiring diagram? If you can, you're in good shape.
The ballast in the picture was made by Advance brands. These are the most common, and almost always have the same wiring code (X1,X2,etc...) and wiring set-up as the one in the pic. However, you may end up buying a different brand which has a
slightly different set up. Let's take a look at my 1000W HPS ballast as an example. This thing was manufactured 15 years ago by a company called "Sola". I have used graphical representation, so that I wouldn't have to take out all the parts for photographing.
If you compare this one closely with the picture of the Advance ballast, you can see some minor differences. There are 3 wires coming from the igniter which are joined with 3 wires from the long side of the transformer. They are all labeled simply 1,2,3 and there are only 2 wires per igniter/transformer connection. In the Advance ballast, you can see that 2 of the igniter wires (X1 and X3) go to connections where there are 3 wires total held by wire nuts.
In this ballast, the only place that there are 3 wires at a wire nut connection is where the white wire from the socket, the "com" wire from the transformer and the white wire from the power cord meet. Slight differences, but the final result is always the same.
High pressure sodium
This wiring description is for an Advance brand ballast. If you end up with a different brand and the wiring doesn't seem quite the same, then it isn't. But it should not be very difficult to figure out the difference after familiarizing yourself with the various wires and parts in the illustrations.
First, orient the transformer so that you know which side is "long" and which is "short". Locate the 2 wires that say "cap" on them. They should be coming from the inside of the transformer bulges. These wires will either get connected directly to the capacitor with little clips (as in my example) or occasionally, with wire nuts to wires coming from the capacitor.
Next, locate the wire coming from the long side of the transformer which is labeled somewhere with the number 3 (or "X3"). Then with a wire nut, connect it to the number 3 wire coming from the igniter. Make sure the nut goes down snugly and that no bare wire can be seen.
Before going any further, you need to figure out how far from the ballast the bulb will be placed. In my example, the wires to the socket are only a foot long so that I could get it in the pic. In real life, the wire will usually be 6 to 10 feet long. Use a piece of heavy duty (extension cord) wire and wire nuts to extend the socket's wires as far as you need to. Just attach black to black and white to white. The green wire is a ground which will get attached to your reflector on one end, and to the transformer base/ballast bow on the other end to prevent against shock.
Then, find the white wire labeled "com X2" (or "com 2" or whatever it is in your particular case) coming from the transformer's short side. While you hold it, get the #2 wire from the igniter (it may also say "com X2" or "com 2" or simply "2") and the white wire from the socket. Screw a wire nut onto all 3 of these wires and make sure the connection is tight with no bare wire showing.
Find the wire coming from the transformer's long side labeled "lamp". Along with the #1 ("X1" or "one") wire from the igniter and the black wire from the socket. As above, connect all 3 wires together with a wire nut.
OK, you're almost done! The last two wires should come from the transformer's short side. One should say "com" and the other "120". These are the two wires that will go to your power cord. Cut your extension cord to the right size and splice until the white, black and green are showing. The white wire gets connected to the "com" wire on the transformer, while the black wire goes with the "120" (or whichever voltage you have) on the transformer. The green wire is the ground and that gets attached to either the ballast box or the base of the transformer to protect against shock.
If you bought a multi-tap ballast, now is the time to deal with that. There should be a wire with a little clip on it attached to 1 of 4 possible spots on the transformer. These 4 options are for 4 different voltages. Find the one labeled "120" (or whatever your voltage is) and attach the wire/clip to that one. Some ballasts simply have a few extra wires inside labeled for different voltages. In that case, find the one for your voltage and strip the insulation off the end, then connect it with a wire nut to the black from the power cord. Make sure to leave the other voltage wires with all their insulation.
http://www.onlinepot.org/grow/_derived/wiringlights.htm_txt_wiring2.gif
Metal Halide
If you want a metal halide light, your task is even easier because now you only have the transformer and capacitor to work with and no igniter. This is for standard metal halide ballasts. On occasion, you run into a MH ballast which has an igniter. Try not to get this kind if you can. If this is the only option, then follow the instructions for HPS ballasts.
Connect the wire labeled "cap" coming from the transformer's long side to the capacitor.
Connect the other wire coming from the capacitor (labeled "lamp") to the black socket wire. (note: see instructions in HPS section on lengthening socket wires if you need to).
The transformers short side will either have 1 or 2 wires coming from it labeled "com". If there is only one, then connect that wire with both the socket's white wire and the power cord's white wire. If there are 2 "com" wires, then pick one and connect it to the socket's white wire. Then connect the other "com" wire to the power cord's white wire.
Connect the power cord's black wire to the transformer's short side wire labeled "volts" or "120" (or whatever voltage you have). See the HPS section for more info on connecting with a mutli-tap ballast.
Testing!
Now, even though it will work without it (and even though it got left out of all the illustrations), I recommend grounding the socket and power cords. The grounds are the green wires coming from these 2 cords. Both of these wires should be attached either to the metal base of the transformer or to the inside of the ballast box if it is made of metal. The other end of the socket ground gets attached to the metal part of the reflector. When I post the instructions on ballast box and reflector assembly, I will include a quick step on doing this.
Ok, double check all your work and make sure you did it right. Are all the wires joined properly? Are all the wire nuts screwed down tightly? Can you see any bare wire sticking out below a wire nut? If you answered uh...yes, yes and no to these questions, then it's time to test fire. Screw the bulb in to the socket, then plug the thing in. It should hum and the bulb should come on almost immediately. If it doesn't or if you see or hear anything unusual, then unplug it. Most likely, if you made a mistake, then the bulb simply will not light. There isn't much chance of a fire or explosion, but you might see a spark or two. You will have to wait about 5 minutes before messing around to figure out what went wrong. This is because the capacitor holds electricity and you may get shocked if you touch the wrong wire. Double check everything and try again.
A quick word about bulbs. High pressure sodium bulbs can be burned in any position. When you buy a metal halide bulb, you need to know what position it will burn in. There are bulbs made only for horizontal placement, base-up placement, vertical (base-down) and universal. The universal bulb can burn in any position, but it is not quite as bright (maybe 5% less) as the position specific bulbs. If you use a specifically horizontal MH bulb, then you also will need a special socket. I will suggest just going with a universal bulb and socket. It makes life easier if you ever change bulb positions.
Now, you could conceivably just put the ballast parts onto a piece of wood, but what you really want is a self contained box to mount the stuff in so it will be protected from water and dirt.
but now im looking to build some of my own equipment ( which so far most of has been homemade ). ive been reading everywhere that it is very simple to but together an HID ballast, which it does look, except for knowing what parts to put together?? i know a hps ballast is made up of a transormer, a cap and an ignitor (MH being the same minus the ign), but what transformer? and what cap? i am looking to be using 70W MH lamp to start with, but where can i source the right parts without buying a kit online? i have alot of old electrical equipment lying around my house and cant help thinking somthing must be of some use?, what should the output voltage/wattage be?
best box yet), but ive only got like 200w of cfl over 3 female plants (bagseed) and wanna finish them off with somthing a bit pokyer, all the streetlamps in my area are either LPS (i think) or have been converted to CFL. i really want to assemble a small HPS or MH setup and know i have the electrical know how to do it, is there ANYTHING in day to day life that contains a transformer suitable for this? or just and output voltage that i should look for. the capacitor will not be a problem as i have many lying around and can easly get more. someone must have made one from scratch?? i have an OLD ossillascope lying around if that could be any use??