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Laptop power adaptors tester

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    Laptop power adaptors tester

    Since I've got to fix a bunch of power adaptors, I will try to make life a bit easier for myself. Instead of storing a few laptops just for testing purposes, I will try to make a universal tester instead.

    It will have different DC input sockets from different laptops, for some of the main laptops.

    Some are 2 pin so they just need voltage reading and dummy load.

    Some are 3 pin, for example HP, Dell and Lenovo. HP will need voltage reading from middle pin, Lenovo will need resistance reading from middle pin and Dell will need a onewire reading from middle pin (got this part done already).

    First it will need to see if it even has a reading from the middle pin. If it does, it will show adaptor data on LCD based on that reading.
    I can compare it to the data written on the adaptor. If all is OK, I will connect dummy load.

    Dummy load would probably consist of 30x 120R 5W resistors, grouped as 12+2+6+6+2+1+1 or something similar, all in parallel and every group has its own switch or relay. This seems like a cheap way to get a load which I can switch as needed, from around 40W to 90W supplies. Or is there any better method? Lightbulbs, heating elements?

    When applying the load, voltage should stay between certain range. How much should the maximum error be?

    Maybe voltage ripple reading would be useful. What could be an okay ripple voltage on these things?

    Any other ideas about this before I start doing anything?
    Data about HP middle pin voltages based on wattage? I have my data but would like to see some semi-official data to back it up

    #2
    Re: Laptop power adaptors tester

    The middle pin of the HP PSUs is from a 1-wire data bus, it's digital...

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      #3
      Re: Laptop power adaptors tester

      Originally posted by eccerr0r View Post
      The middle pin of the HP PSUs is from a 1-wire data bus, it's digital...
      Any proof on that? I see a 1N4148 diode and 4403 (PNP) transistor (and caps, resistors) in ID circuit. Dell is the one with onewire data bus.

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        #4
        Re: Laptop power adaptors tester

        Don't know for sure, if it's simply voltage then it should be easy enough to get a proper load for it.

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          #5
          Re: Laptop power adaptors tester

          No need to load the ID pin. That's just to know the rated wattage.

          A few of the last chargers batch.
          Middle value is ID pin voltage.
          45W - 13.1V 19.6V
          65W - 14.3V 19.8V
          65W - 14.3V 19.8V
          65W - 14.2V 19.7V
          65W - 14.1V 19.6V
          65W - 14.4V 20.0V
          65W - 14.2V 19.6V
          90W - 15.1V 19.5V
          90W - 15.2V 19.6V
          90W - 15.1V 19.5V
          90W - 15.5V 20.0V
          40W - 12.3V 19.5V
          45W - 13.1V 19.6V
          40W - 12.5V 20.0V
          65W - 14.2V 19.6V
          230W - 17.3V 19.6V

          So it seems like 40W around 12V, 45W around 13V, 65W around 14V, 90W around 15V.

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            #6
            Re: Laptop power adaptors tester

            proper load for the power supply that is.

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              #7
              Re: Laptop power adaptors tester

              Well yes, that I knew from the start. I was just wondering if anybody has a link to some data about it, without me finding every HP power supply with different wattage to be able to include it in the program.

              For some strange reason, the onewire method that Dell uses is documented very well, but it's not as easy as HP's method, where you can just measure between ground and middle pin.

              With Dell, you just need to read data from it using something that can communicate using onewire and it gives you something like DELL00AC090195046CNblablabla, where you can read that 090 = 90W, 195 = 19.5V, 046 = 4.6A.

              Lenovo uses 2 wires, but has a 3 pin plug. There's just a resistor between ground and middle pin.
              http://www.thinkwiki.org/wiki/Power_Connector

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                #8
                Re: Laptop power adaptors tester

                Well, again, doesn't look very hard to linear interpolate/extrapolate it, did something like this for a table of NTC thermistor values to get those in-between values.

                It looks like every two volts, it doubles the wattage. Easy enough to use that as a start.

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