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???
09/13/06 12:38
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 		 #124186 - USB?
Responding to: ???'s previous message
As Erik says, RS-232 is not designed to supply power. Period.

There are, of course, many devices that do seem to manage to do it - but can they guarantee that they will always work with absolutely any RS-232 port?

If you can take the risk on the uncertainty, go ahead - just Google for the very many "circuit ideas" that will describe this all over the web.

But, as you specifically mention PCs, why not use USB?
USB is specifically designed to supply power!
Plus, we see an increasing number of posts here and elsewhere noting that PCs often don't have RS-232 ports these days!

List of 49 messages in thread
TopicAuthorDate
Getting Power from PC RS232?            01/01/70 00:00      
   maybe            01/01/70 00:00      
      USB?            01/01/70 00:00      
   Serial port power links            01/01/70 00:00      
      the most abused "design criteria"            01/01/70 00:00      
   This circuit usually works            01/01/70 00:00      
      Kai, you disappoint me            01/01/70 00:00      
         I'm not here to amuse you...            01/01/70 00:00      
            no amusement seen            01/01/70 00:00      
      More pin options            01/01/70 00:00      
         A couple of questions            01/01/70 00:00      
      just a note...            01/01/70 00:00      
         Not so simple...            01/01/70 00:00      
            rs232 to rs485            01/01/70 00:00      
               Why not USB?            01/01/70 00:00      
                  usb?            01/01/70 00:00      
                     See reply to your duplicate post            01/01/70 00:00      
                     You need to specify better what you want.            01/01/70 00:00      
               you should have had a look            01/01/70 00:00      
                  You can, but...            01/01/70 00:00      
                  it has to drive 5 volts into 100 ohms            01/01/70 00:00      
                     Various loads            01/01/70 00:00      
   serial mice have been doing this for years, but...            01/01/70 00:00      
      These schemes work despite deviations from standar            01/01/70 00:00      
         Pins 9 & 10 on DB25            01/01/70 00:00      
            For the record, RS 232 power is a bad idea.            01/01/70 00:00      
               commercial device powered by RS232            01/01/70 00:00      
                  definitions and opiunions            01/01/70 00:00      
   usb            01/01/70 00:00      
      More Info Required            01/01/70 00:00      
      standard "USB port" response            01/01/70 00:00      
         You really don't want to do that            01/01/70 00:00      
            USB only hurts the first time            01/01/70 00:00      
            COMx: vs USB            01/01/70 00:00      
               Acronyms            01/01/70 00:00      
                  silly game!            01/01/70 00:00      
                     More Silly Game, SMSers should like this.            01/01/70 00:00      
                        did you fo to the Bean Pot            01/01/70 00:00      
                           It's been around awhile            01/01/70 00:00      
               is that Arizona, Mars            01/01/70 00:00      
   usb?            01/01/70 00:00      
      I don't think so...            01/01/70 00:00      
         SiLabs            01/01/70 00:00      
      oy            01/01/70 00:00      
         Cost?            01/01/70 00:00      
            Budget            01/01/70 00:00      
               cost?            01/01/70 00:00      
                  Cost!            01/01/70 00:00      
                     it has 2 slaves as well            01/01/70 00:00      

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