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Re: [tracker2] Power From Laptop

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  • 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 1 of 9 , Feb 2, 2009
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      > 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 2 of 9 , Feb 2, 2009
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        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 3 of 9 , Feb 2, 2009
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          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 4 of 9 , Feb 2, 2009
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            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 5 of 9 , Feb 2, 2009
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              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 6 of 9 , Feb 2, 2009
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                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 7 of 9 , Feb 3, 2009
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                  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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