Why is Motorola USB not Blackberry USB (chargers = 5.0v, 5.9v, 350ma, 500ma)
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From: tim on 1 Jan 2007 22:35 Emily <emilymoberg(a)hotmail.com> wrote in news:spnts0u0xuzp$.l5ddai2xzpbc.dlg(a)40tude.net: > Is it true that one MUST use ONLY the EXACT USB charger that > comes with their cell phone or digital camera? > > Are USB chargers really not interchangable? > > The T-Mobile store told me I could only use their T-Mobile > charger for my new USB based cellphone. After showing me the > charger for the Motorola V195 which is 5.9 volts 375ma, they > then opened a desk drawer and handed me three melted USB > chargers from blackberrys & digital cameras, one at 5.0 volts, > 750ma; another at 5.0 volts, 550 ma, and yet another at 5.2 > volts 450 ma. > > Can we swap these supposedly USB chargers or not? > - Blackberry TCPRIM2ULSSN 5.0vdc 750mA > - Motorola PSM5037B 5.9vdc 375mA > - Motorola DCH3-05US-0300 5.0vdc 550mA > - Motorola FMP5185B 5.2vdc 450mA > > Why is Blackberry USB different than Motorola USB which is > different in and of itself? Can we swap these USB chargers or > must we stick to the charger that came with the device? > > Emily If a device is going to use the USB connector to supply input voltage for charging, it MUST be able to charge when connected to a USB port on a computer, which is a nominal 5.0 volts. (I am sure there is a minimum current that must be available as well...) There are several different ways in common use to limit input voltage to a given level (in this case 5.0v). Most can dump up to about a volt over without overheating or otherwise letting the magic smoke out. In that case all four of the above power supplies should be adequate for your device. On the other hand, if, as one poster suggested, they are merely using USB connectors because of their ubiquitesness (read availability [I always wanted to use that word someplace!]) then all bets are off. If that is the case, then connecting to a real live USB port will probably NOT charge the device properly if at all. I could see in certain circuit configurations an increase in current demand to attempt to make up the deficiency in voltage, with the suggested results. First off, read the documentation. If it explicitly tells you that a computer USB port will not work, or that the device should never be plugged into such a port, then case #2 applies and all bets are off. If the documentation states that a real USB port can be used to supply charging voltage, then its pretty much anything that comes close should work. I personally lean towards case #1, and believe that the other supplies were fried by some other factor. One that comes to mind would be trying to charge an almost totally dead device while trying to use it at the same time. That will definately up the power requirements to the point that it would be no surprise to have a unit melt down.
From: Rich Grise on 2 Jan 2007 16:56 On Tue, 02 Jan 2007 03:35:12 +0000, tim wrote: > On the other hand, if, as one poster suggested, they are merely using > USB connectors because of their ubiquitesness (read availability [I > always wanted to use that word someplace!]) Use "ubiquity". You'll sound much more sophisticated. ;-) Cheers! Rich
From: Richard Thomas on 15 Jan 2007 23:23
On Fri, 29 Dec 2006 16:39:54 GMT, "Jon Slaughter" <Jon_Slaughter(a)Hotmail.com> wrote: >Note though that these are MAX current safety ratings. They are the maximum >possible current that the device will draw with some headroom for safety at >the specified voltage. So in reality your Blackberry might only use 100mA >on avg. For example, I have some security cameras that use 80mA at 8V in >daytime but at night use 160mA because it switches to IR. Here I would need >a power supply that will deliver atleast 200mA(but at ~8V). Well, that is >unless I knew that the camera would not be ran at night and there would be >no way the "night vision" would be used(like if I disabled the photo sensor >to make sure). It's also worth pointing out that in many cases, the charger may not have been designed specifically for the device in question but may be an "off the shelf" power supply "guts" with a USB (or other) adaptor thrown on the end and a case with a Motorola/Nokia/Rim logo added for looks. The charger may actually be able to supply much more than what is actually required simply because that was the cheapest choice. >> DEVICE = Motorola V195 SUPPLY = PSM5037B 5.9vdc 375mA > >Is using 5.9V which is almost a full volt over. There could be many reasons >for this. Maybe the power supply is wrong. Maybe the device does not conform >to the USB spec. Definitely way outside the spec (5%). If I had one of these, I might be tempted to junk it just to be on the safe side. However, a quick search shows that this is the old V400 style charger and /not/ USB. >Essentially power supplies with the same connectors and same voltage are >interchangble if they can supply the maximum current the device uses. Unfortunately, that is not the end of the story. The USB spec also states that a device should negotiate the current that it is supplied to it. Some devices don't worry about this and will happily charge as long as there is 5V on the pins but, for example, my Motorola SLVR requires more than that to charge. If I plug it in to a USB cable that is plugged into a 12V cigarette lighter adapter, it will not charge and will act as if it is not plugged in at all. However, if that same cable is plugged in to a computer, it will fire up fine. I also have a car charger that works no problem. My wife's RAZR (may it rest in peace) wouldn't even charge on a computer unless you installed the Motorola drivers first. My Palm TX will charge properly with my sync/charge cable (puts power in the little square plug) but if I just use the USB sync cable that came with it, if plugged into a computer, it will charge normally but if plugged into the 12V adapter, the charge indicator will not come on (it will however charge extremely slowly). This is about to become an issue for me as I'm planning on installing a mini-USB connector in the Palm in the next couple of days. I never seem to be able to put my hands on a Palm cable when I need it but mini-USBs are ubiquitous now (Dollar Tree was selling retractable ones for $1 until recently). So in short, no, not all USB chargers are equal. They /should/ give you the 5V and they /should/ be able to supply the current you need (if they conform to spec which is by no means guaranteed) but even at that point, you need to know if your device can be charged with a dumb charger and whether the charger is dumb or not. Rich Oh, just remembered, my GPS, which is happy with dumb chargers, will not charge with my Motorola USB non-dumb charger. So presumably the charger is not willing to supply the current until negotiated with? It's all fun and games I guess :D -- I am free, no matter what rules surround me. If I find them tolerable, I tolerate them; if I find them too obnoxious, I break them. I am free because I know that I alone am morally responsible for everything I do. --Robert A. Heinlein |