FYI: MAh is incorrect. The correct abbreviation is mA. Lower-case m for the milli prefix (uppercase is Mega with is times 1000 instead of divide by 1000). There's no H because that refers to hours. You would, however, have an H when describing things like battery capacity because it refers to how many hours the battery can put out power at 1 mA at the battery's voltage rating but then they'd usually use watt-hours.
If electricity was a waterfall, volts would be how tall the water had to fall and amps would be how much water is actually falling. Commonly devices are spec'ed by the voltage requirement and ampere requirement or a wattage (watts) requirement. For Direct Current (DC) Circuits such as the usb power, the relationship between those three is watts equals volts times amps. This is known a ohm's law. For USB devices the standard specifies 5 volts DC. If a device needs more power the max is 500 milliamps or half an amp. Using an unpowered usb takes 100 mA right off the top so any device attached has a limit of 400 mA. Using a powered USB Hub (plug in the AC outlet type) they can supply 500 mA to every port because it's not coming from the PC's (or Braillenote's) power. - Chris On Wed, Jul 1, 2009 at 12:36 AM, Joseph Lee<[email protected]> wrote: > Hi Kristen and list, > I did some research about milliamp (via Google, Wikipedia and Oxford > Dictionary), and here's what I found: > An amp, properly called "ampere," is the unit of measurement of electric > current. In other words, it measures how much electric current goes through > electric circuit (more technically, conductors) in one second. A milliamp > (MAh for short) is one thousandth of an amp. > Er, any electrical engineers or people who are into physics, is there a > simpler explanation... > Hope it is simple enough. > Cheers, > Joseph > -----Original Message----- > From: Kristen Ashley Slemp [mailto:[email protected]] > Sent: Tuesday, June 30, 2009 7:35 PM > To: Joseph Lee; [email protected]; [email protected]; > [email protected] > Subject: RE: [Braillenote] External Hard Drive Again > > Hello Joseph and Everyone, > IS ("milliamps") AN ABBREVIATION Or IS IT A WHOLE TERM?!? > AND WHETHER IT'S AN ABBREVIATION OR A TERM WHAT DOES IT MEAN?!? > THANK YOU! > SINCERELY, Kristen > >> ----- Original Message ----- >>From: "Joseph Lee" <[email protected] >>To: "'Alex Hall'" <[email protected]>, > <[email protected]>,<[email protected] >>Date sent: Wed, 24 Jun 2009 20:54:11 -0700 >>Subject: RE: [Braillenote] External Hard Drive Again > >>Hi Alex, >>Actually, from my research, when USB devices are first connected > to a host >>(such as BrailleNote), it will start out with 100 milliamps. When > the host >>says to switch to higher power, then it will switch to maximum > power output >>- 500 milliamps. A USB hub, regardless of number ports, is > supposed to >>provide a total of 500 milliamps. For instance, a four-port UsB > hub can use >>100 milliamps to power itself, plus 4X100 milliamps for devices > connected to >>it. >>I think in theory, USB hubs with devices attached will work with >>BrailleNote. Most come with UsB plus an aC adapter for power. >>Cheers, >>Joseph P.S. if it is not FAT, try using a drive format software > to convert >>it back to fAT32. > >>-----Original Message----- >>From: [email protected] >>[mailto:[email protected]] On Behalf Of Alex > Hall >>Sent: Wednesday, June 24, 2009 8:32 PM >>To: [email protected]; [email protected] >>Subject: re: [Braillenote] External Hard Drive Again > >>Not a hub, but an external drive? Sure! Mine is a 320gb Seagate >>that works perfectly. If you have a hub it should work. Both >>ports can put out 500 milliamps between them, but, as I >>understand it, one port could put out 500 and the other can be >>inactive, or one can give 200 and the other 300, and so on (I >>assume this from the wording of the manual). Therefore, the one >>working port on your machine should give you the power required, >>and all you need is the hub to give you both ports (data and >>power). Hope that makes sense! > >>Have a great day, >>Alex > >>> ----- Original Message ----- >>>From: "Nicole B. Torcolini" <[email protected] >>>To: "'Braillenote List'" <[email protected] >>>Date sent: Wed, 24 Jun 2009 20:19:59 -0700 >>>Subject: [Braillenote] External Hard Drive Again > >>>Some of you may remember that I got an external hard drive for >>Christmas and >>>was trying to hook it up to my Mpower 7.5. At the time, I gave >>up because >>>the bn could not provide enough power, one of my USB's being >>broke. I now >>>have a USB hub. The drive is 160 gb and it is not fat format. >>Has any one >>>had any luck with an external hard drive and a usb hub with the >>bn? > > > >>>___ >>>Replies to this message will go directly to the sender. >>>If your reply would be useful to the list, please send a >>>copy to the list as well. > >>>To leave the BrailleNote list, send a blank message to >>>[email protected] >>>To view the list archives or change your preferences, visit >>>http://list.humanware.com/mailman/listinfo/braillenote > > >>___ >>Replies to this message will go directly to the sender. >>If your reply would be useful to the list, please send a >>copy to the list as well. > >>To leave the BrailleNote list, send a blank message to >>[email protected] >>To view the list archives or change your preferences, visit >>http://list.humanware.com/mailman/listinfo/braillenote > >>No virus found in this incoming message. >>Checked by AVG - www.avg.com >>Version: 8.5.339 / Virus Database: 270.12.90/2199 - Release Date: > 06/24/09 >>12:49:00 > > >>___ >>Replies to this message will go directly to the sender. >>If your reply would be useful to the list, please send a >>copy to the list as well. > >>To leave the BrailleNote list, send a blank message to >>[email protected] >>To view the list archives or change your preferences, visit >>http://list.humanware.com/mailman/listinfo/braillenote > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 8.5.339 / Virus Database: 270.13.0/2209 - Release Date: 06/30/09 > 11:37:00 > > > ___ > Replies to this message will go directly to the sender. > If your reply would be useful to the list, please send a > copy to the list as well. > > To leave the BrailleNote list, send a blank message to > [email protected] > To view the list archives or change your preferences, visit > http://list.humanware.com/mailman/listinfo/braillenote > > ___ Replies to this message will go directly to the sender. 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