Using the your PC’s internal power supply to directly power an external devices is in my opinion a real bad idea…
AGREE! 
Why not? There are many things you can buy that are powered by USB. I seen a USB cup warmer, USB clock, USB fish tank (fake fish), USB you-name-it! They are all powered by USB.
well if your gona just run programs on the atom bot board, I guess there is no harm. If you plan to run 20 servos from this source, the servos will cause a nice load and who knows what might happen.
And they all draw under 500ma (0.5A) OR have their own external power supply.
So if you power the servos from somewhere else you can probably power the micro part from the 5V, but do not try to power the servos from the USB or you risk smelling the special smoke.
Well, there’s always the DIY approach to making a power supply.
Going from memory, what’s needed is a transformer (two inductors, a.k.a. “coils”, wrapped around an iron ring) to step down the voltage.
Then a fullbridge rectifier (that’s just four diodes aranged nicely) to modify the AC sin wave into a positive “bouncing” current.
And then a bunch of filter caps (and an inductor?) to smooth out the “bounce” into a proper DC current.
Anyone done this before?
I think I found this in a Digital Electronics book that I got from the library.
When I go back, next, I’ll see if I can get it again, so I can post a schematic.
Now you’re talking about commercial devices! Before you were talking about soldering wires onto a DB9, which is directly powering something from the PC’s internal power supply! The USB port may be fused, or some other protection may be in place.
No, I am saying you can power external things using the pc’s power supply.
Ug…
Look at what I quoted you. You were talking about the DB9, not USB!
Hes all over the map Jim… All over… 
And, whats that supposed to mean?
Actually Jim, I was talking about both. DB9 and USB. I mentioned that USB has a 5v power thingy in one of its pins and thought that might be useable for a powersupply while your developing with the ABB or SSC-32… I also asked if it would be possible to somehow get 6v to the DB9 from the computer’s internal power supply.
You confused me now.
The USB port can probably power the boards, but not any attached motors. Most computer power supplys supply +5v and +12v. The +12v supply is usually weak compared to the +5v part. You can use a +5v regulator and a diode or LED on the regulator ground to get colse to +6v when connected to the +12 supply. I wouldn’t try powering any motors from the computer power supply. External power supplys are fairly inexpensive.
f10.putfile.com/thumb/8/21516154599.jpg
Above is the promised schematic out of the library book.
I can’t help anyone out with specific part numbers, since I haven’t built this circuit myself, nor plan to.
I don’t like playing with household AC, when I can help it.
Looking at this, though, I’m wondering if you’d even save money buying the parts and making it yourself, since a regulated 5V wallwart is only about 15 bucks.
::points down at red disclaimer::
I will not be held liable, nor pay your medical bills, or even rush over to the hospital to pat your hand and mutter simpathies when you electricute your self.
Be warned.
getting eletricvuted isn’t that bad 
you need to be ready though
Ya, I found that out while cutting two 7.2 v battery wires at the same time!!! It still hurts…lol
only 7.2, try 120 VAC
Building a robot: $500
cost of tools: $100
Cost of Battery: $25
1 idiot shocking himself while trying to solder batteries together: PRICELESS!!
There are somethings a hobbyist can’t buy, but for everyone else theres LYNXMOTION!!!
Uh, well you have an idea what it feels like anyway. 
Nick, do you want to tak about this circuit or are you just fulfilling a mission to post it? It graphically potrays the concept at an acceptable level but it needs some help with the text and values shown. I’ll just leave it at that unless people want to talk more.
Yeah Nick… What the heck are you doing?
JK
Feel free to talk away as much as you’d like.
I don’t intend to play with household AC anytime soon, but extra information never hurts.
AFAIK, the values there can be explained as follows:
.1A fuse because .1A * 14 = 1.4A DC output, which should be both safe and sufficient for most electronics needs.
14:1 ratio because it outputs high enough voltage to allow for the 7805’s dropout.
10uF and .1uF cap because those are the generic bulk filter and
And, I call it “bouncing” because that’s what the graph of the absolute value of a sin wave looks like.
I’m guessing that the transformer won’t actually output the ideal 7.9VAC, but I’m not familiar with the efficiencies of transformers, so I don’t know how much that should be derated.
How’s that sound?