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Re: [tracker2] Power From Laptop

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  • 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 1 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 2 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 3 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 4 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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