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Power From Laptop

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  • Adam Sherman
    Is it possible to get power via the serial port on a laptop? Thanks, A. -- Adam Sherman me@va3shr.ca VA3SHR
    Message 1 of 9 , Feb 2, 2009
      Is it possible to get power via the serial port on a laptop?

      Thanks,

      A.

      --
      Adam Sherman
      me@...
      VA3SHR
    • Scott Miller
      Nope, not to any useful degree. You can sometimes steal a few mA, but that s about it. Scott
      Message 2 of 9 , Feb 2, 2009
        Nope, not to any useful degree. You can sometimes steal a few mA, but
        that's about it.

        Scott

        Adam Sherman wrote:
        >
        >
        > Is it possible to get power via the serial port on a laptop?
        >
        > Thanks,
        >
        > A.
        >
        > --
        > Adam Sherman
        > me@... <mailto:me%40va3shr.ca>
        > VA3SHR
        >
        >
      • Jason Rausch
        ... I have leeched power off of a serial port before to power an ST202, but that was about it. Took power from the RTS and DTR lines to a large cap. Pretty
        Message 3 of 9 , Feb 2, 2009
          > Is it possible to get power via the serial port on a laptop?

          I have "leeched" power off of a serial port before to power an ST202, but that was about it. Took power from the RTS and DTR lines to a large cap. Pretty much trickle charged the cap to get the ST202 going.

          I have no idea what kind of current these lines are good for though.

          This is a schematic I came up with to interface a TNC to my old Palmspring Visor, years ago:

          http://www.ke4nyv.com/ttltoserial.jpg

          Jason KE4NYV
          RPC Electronics
          www.rpc-electronics.com

          --- On Mon, 2/2/09, Adam Sherman <adam@...> wrote:

          From: Adam Sherman <adam@...>
          Subject: [tracker2] Power From Laptop
          To: tracker2@yahoogroups.com
          Date: Monday, February 2, 2009, 1:39 PM


















          Is it possible to get power via the serial port on a laptop?



          Thanks,



          A.



          --

          Adam Sherman

          me@...

          VA3SHR
        • Tyson S.
          You can try the USB, I think it s 5 Volts. They make coffee cup warmers powered by them. ________________________________ From: Scott Miller
          Message 4 of 9 , Feb 2, 2009
            You can try the USB, I think it's 5 Volts. They make coffee cup warmers powered by them.


            From: Scott Miller <scott@...>
            To: tracker2@yahoogroups.com
            Sent: Monday, February 2, 2009 10:43:38 AM
            Subject: Re: [tracker2] Power From Laptop

            Nope, not to any useful degree. You can sometimes steal a few mA, but
            that's about it.

            Scott

            Adam Sherman wrote:

            >
            >
            > Is it possible to get power via the serial port on a laptop?
            >
            > Thanks,
            >
            > A.
            >
            > --
            > Adam Sherman
            > me@... <mailto:me%40va3shr .ca>
            > VA3SHR
            >
            >


          • Fred Hillhouse
            100mA is usually no problem and possibly up to 400mA. But there is no guarantee above 100mA. _____ From: tracker2@yahoogroups.com
            Message 5 of 9 , Feb 2, 2009
              100mA is usually no problem and possibly up to 400mA. But there is no guarantee above 100mA.
               


              From: tracker2@yahoogroups.com [mailto:tracker2@yahoogroups.com] On Behalf Of Tyson S.
              Sent: Monday, February 02, 2009 13:58
              To: tracker2@yahoogroups.com
              Subject: Re: [tracker2] Power From Laptop

              You can try the USB, I think it's 5 Volts. They make coffee cup warmers powered by them.


              From: Scott Miller <scott@opentrac. org>
              To: tracker2@yahoogroup s.com
              Sent: Monday, February 2, 2009 10:43:38 AM
              Subject: Re: [tracker2] Power From Laptop

              Nope, not to any useful degree. You can sometimes steal a few mA, but
              that's about it.

              Scott

              Adam Sherman wrote:
              >
              >
              > Is it possible to get power via the serial port on a laptop?
              >
              > Thanks,
              >
              > A.
              >
              > --
              > Adam Sherman
              > me@... <mailto:me%40va3shr .ca>
              > VA3SHR
              >
              >


            • Wes Johnston, AI4PX
              If I recall correctly, the rs232 spec says there is a 300ohm resistor in series with each output pin. It s a current limiter by default. Should give about
              Message 6 of 9 , Feb 2, 2009
                If I recall correctly, the rs232 spec says there is a 300ohm resistor in series with each output pin.  It's a current limiter by default.    Should give about 40mA.   Very often, you can rewire an output pin to put 12v on it... the good news is that +/-12v is safe on rs232 due to a 3k ohm input impedance on any device you would plug in... so it won't fry your TNC or serial mouse. 
                 
                I have to agree with another poster... safer bet is to leech power from USB.
                 
                Wes

                On Mon, Feb 2, 2009 at 1:39 PM, Adam Sherman <adam@...> wrote:

                Is it possible to get power via the serial port on a laptop?

                Thanks,

                A.

                --
                Adam Sherman
                me@...
                VA3SHR




                --
                Wes
                ---
                You can't get rid of poverty by giving people money.

                It may be necessary temporarily to accept a lesser evil, but one must never label a necessary evil as good.
              • Jason KG4WSV
                ... The USB spec says any peripheral gets 100mA by default. Up to 500mA may be available, but it requires some negotiation to get more than 100mA. In reality,
                Message 7 of 9 , Feb 2, 2009
                  On Mon, Feb 2, 2009 at 1:30 PM, Fred Hillhouse <fmhillhouse@...> wrote:
                  > 100mA is usually no problem and possibly up to 400mA. But there is no
                  > guarantee above 100mA.

                  The USB spec says any peripheral gets 100mA by default. Up to 500mA
                  may be available, but it requires some negotiation to get more than
                  100mA.

                  In reality, I think some ports just give you 500mA.

                  -Jason
                  kg4wsv
                • Adam Sherman
                  ... Thanks for the overwhelming amount of replies! The end conclusion is that a serial-USB adapter than would power the Tracker should be possible. I m going
                  Message 8 of 9 , Feb 2, 2009
                    On 2-Feb-09, at 13:39 , Adam Sherman wrote:
                    > Is it possible to get power via the serial port on a laptop?


                    Thanks for the overwhelming amount of replies!

                    The end conclusion is that a serial-USB adapter than would power the
                    Tracker should be possible. I'm going to investigate.

                    A.

                    --
                    Adam Sherman
                    me@...
                    VA3SHR
                  • P. Suryono Adisoemarta
                      I made a pigtail on the null-modem cable for OT+, with a short cable to plug to the USB port of the laptop, to tap the 5V line (leftmost pin) and deliver
                    Message 9 of 9 , Feb 3, 2009
                       
                      I made a pigtail on the null-modem cable for OT+, with a short cable to plug to the USB port of the laptop, to tap the 5V line (leftmost pin) and deliver it to Pin 4 on the DB9 to OT1 series (or OT2m).
                      73 de Paulus N5SNN / YD0NXX
                       

                      --- On Mon, 2/2/09, Adam Sherman <adam@...> wrote:
                      From: Adam Sherman <adam@...>
                      Subject: [tracker2] Power From Laptop
                      To: tracker2@yahoogroups.com
                      Date: Monday, February 2, 2009, 12:39 PM

                      Is it possible to get power via the serial port on a laptop?
                      
                      Thanks,
                      
                      A.
                      
                      -- 
                      Adam Sherman
                      me@...
                      VA3SHR
                      
                      
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