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, thereās always the DIY approach to making a power supply.
Going from memory, whatās needed is a transformer (two inductors, a.k.a. ācoilsā, wrapped around an iron ring) to step down the voltage.
Then a fullbridge rectifier (thatās just four diodes aranged nicely) to modify the AC sin wave into a positive ābouncingā current.
And then a bunch of filter caps (and an inductor?) to smooth out the ābounceā 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, Iāll see if I can get it again, so I can post a schematic.
Now youāre talking about commercial devices! Before you were talking about soldering wires onto a DB9, which is directly powering something from the PCās 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 pcās power supply.
Ugā¦
Look at what I quoted you. You were talking about the DB9, not USB!
Hes all over the map Jimā¦ All overā¦ 
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-32ā¦ I also asked if it would be possible to somehow get 6v to the DB9 from the computerās 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 wouldnāt 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 canāt help anyone out with specific part numbers, since I havenāt built this circuit myself, nor plan to.
I donāt like playing with household AC, when I can help it.
Looking at this, though, Iām wondering if youād 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 isnāt 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 hurtsā¦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 canāt 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. Iāll just leave it at that unless people want to talk more.
Yeah Nickā¦ What the heck are you doing?
JK
Feel free to talk away as much as youād like.
I donāt 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 7805ās dropout.
10uF and .1uF cap because those are the generic bulk filter and
And, I call it ābouncingā because thatās what the graph of the absolute value of a sin wave looks like.
Iām guessing that the transformer wonāt actually output the ideal 7.9VAC, but Iām not familiar with the efficiencies of transformers, so I donāt know how much that should be derated.
Howās that sound?
Hmm, I typed up sort of an analysis and info on how you go about designing a linear power supply like this but I am not sure if it is right to post it here in this thread. If you want to start a power supply thread somewhere with your diagram Iāll post the chunk of text I wrote for it.
::twitches nose::
::wiggles ears::
::nods head::
POOF!
Your wish is my command:
lynxmotion.net/viewtopic.php?p=8796#8796