I've seen a lot of folks using PC power supplies to get that 12v in the PJ...

As I'm trying to keep my build as compact as possible doing that is just too large

So I started searching the web for alternatives and came across this.

Has anyone done anything similar?

Something like that is a workable option. The more DIY the better I guess!

Usually, it's pretty easy to find something small lying around though.

All depends on your situation I suppose.

Well, I suppose I could always run to radioshack and get a 12v wall wart and strip the casing off it and desolder the leads from the AC plug

If your house is anything like mine, you probably have a drawer full of ac/dc adapters that go to things that have long since kacked out. Just use one of those. Mine is from a Sony Cd player. As an added bonus, it also has a shielded core and seems to filter a small amount of noise. Pre designed by an expert and cheap to boot. Dont have any? go to your local recycler. They cant give the things away.

SJ

How I wish it was! My household is just getting started. My fiancee moved in with me about 3 months ago and our 2 bedroom apartment is just starting to take shape. We don't have a 'junk' drawer yet as everything is still original and in use!

Naturally the 2nd bedroom is full of my computer gear with little to no space to move around in

It's making building the box for my PJ quite interesting as the only space I have to work is out on our 2nd floor porch! (This is why I'm trying to go as small as possible)

I think what I'm going to do is price the wall warts at Radio Shack then price the cost of the components to build a 12v power supply. I'll do whichever is cheaper...unless...I build a controller board for the PJ. I'm still undecided, but I'm thinking I might like to have one integrated controller for everything, focus, fans, power, and temp.

Go figure, I like to do things the hard way

I gradumatated with an engineering degree a year and a half ago, but I don't have much of an electrical background...more dynamics and design. Looking at that diagram, I could probably build it, but I wouldn't trust myself to do it right the first time or the second...or even the third. Its more worth my time and effort to find one or buy one. I'll take the easy way out.

Radio Shack was rather overpriced when I checked last week: $20 for a 12V 1000mA adapter. I hit up most major department stores' electronic sections and found a decent one at Wally World: $17 for a 3v-12v 1300mA. I like the idea of switching the voltage to my fans to reduce the noise

Wally world! Now there's a place I wouldnt have thought to look for a 12v adapter. May have to swing by there this evening and see if ours has them.

check out allelectronics.com and pick one up for $3 + shipping

walmart should have them for $5 or so.. maybe not the 1300ma version, but 500ma which should be fine for a few fans

The concept of a power supply like the one you linked is pretty simple: The transformer gives you some AC voltage > 12v (18v in this case), the pretty square of diodes chops the negative half of the resulting sin wave and flips it over, giving you a series of half sins going between 0 and 18v (instead of -18v to 18v, which is what you started with), and the capacitors store charge and flatten those half-sins out. The tricky part is making the resulting slighly lumpy >12v output be 1) flat and 2) 12v, which is where the regulator comes in.

With that said, I'd recommend buying one of the same tiny little supplies that come with nearly all little electronic devices - they'll most certainly be smaller than what you'll build, and they'll definitely be cheaper than the parts. Unless, of course, you're interested in learning more about building DC power supplies, which is never a bad reason to build anything

I went into The Source (Canada's rebranded RadioShack) where i found a 120v -> 24V (center tapped 12V) 2 amp transformer for 9.99 CAD. With a AC to DC rectifier i should be able to power all the 12V components I need.
I dont know where one can find a 2 amp wall AC to DC transformer so this should be a good option. I will just put it in with my existing external ballast box.

Typical 7812 voltage regulators top out at 1 to 2 amps. Often the filter caps specificed are good for low to nominal loads... but ripple could be a problem at high loads larger caps might help but the inrush current might overload the regulator. Heat Syncs will definately be need less you let out the magic smoke. With any power components safety glasses are a must a 7805 exploded on me once, granted I did hook it up backwards.

If you look around linear power supplies plans you will find many use the 78xx regulators to control an array of power transistors to provide a greater current handling.

A "good" way to get AC/DC adapters are from ADSL providers, most
(here in Sweden that is) just lend the DSL equipment to the customers
and when the customers end the account they return the modem, BUT
they don't resell the modem to the next customer (since it's probably
outdated)

Things to think about when asking for used stuff.

1. Be nice!
2. Be Polite
3. Use a good and correct language
4. Tell them the truth what you need it for

My finding so far.
BBB = 12 AC/DC adapters 13.8 v 1 A
TELIA = 20 Modem boxes with everything (cables,AC/DC 12v 1A,-
Modem) Had to promise not to resell them but hey it was free
Glocalnet = A very rude "SOD OFF" from the modestly handsome receptionist

This is more or less what I got from writing mail and making phone calls it's
easy and as you can see quite rewarding if you have the hobbies that we have

Someone mentioned junkyards as a good place and they were CORRECT! To
make that place even better bring donuts, I did this and now they call me when
they have stuff that they know I might be interested in.

/Nole

In the first circuit mentioned[assuming the secondary voltage is no more than 30Vp] you can change the regulator to a LM317 and us it to vary the output voltage from ~28-1.2v which may be usfull

So I may be running 2 120mm fans designed for a PC case. Also a 7" lcd monitor. Would it be better to have 2 stripped 120vAC to 12vDC wall warts or 1? Also if I go over on the amps will it obliterate the LCD or the fans? I dont have too much info on the LCD yet, as im waiting to take delivery on it. I just dont want to blow anything out before I have a chance to install them.

Try the Thrift Store you be suprise what you can use for next to nothing in price.

RR

Yeah wall warts at thrift stores work great... i think I spent 2 bucks on mine... and remember that you dont necessarily need 12v.... if youve got an especially loud and high volume fan, you can under-volt it to say 9v and reduce the noise (assuming the fan is decent), just make sure the reduced volume is enough for your cooling needs. The only fans ive been told dont like the under-volting are the Scythe S-flex... badass super quiet (i think between my two in my projecor its like 18 db for just under 100 CFM...).