ThinkPad adapter resistor values

Discussion in 'Lenovo' started by zsero, Aug 2, 2012.

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  1. zsero

    zsero Notebook Deity

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    Upon looking for ways to use the W520/W530 with lighter adapters we've started figuring out at forums.thinkpads.com how a ThinkPad identifies what adapter is plugged in.

    The findings are the following:
    1. There is only 2 wires coming out from the adapter
    2. There are 3 connectors in the plug
    3. The electricity is between the inner and the outer side connector on the circle
    4. The inside pin is used to identify the adapter, by a simple resistor connected between the pin and the outside connector.

    [​IMG]

    So to identify what adapter is what, we need to measure the resistance values between the outside metal and the inner pin.
    • 65W adapters have 10K resistance, confirmed.
    • 90W adapters have no connection, confirmed.
    • The 170W adapter has 1.5K resistance, confirmed.

    What I would like to ask, if you have a ThinkPad adapter, could you measure the resistance between the inner pin and the outside of the circle?
     
  2. power7

    power7 Notebook Evangelist

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    Well done! So it looks like getting 90W to work with W520 should be easy.

    Same 10K/no connection/1.5K as above for 65/90/170W adapters I have.
     
  3. zsero

    zsero Notebook Deity

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    Did you measure the 90W? Just because it wasn't confirmed before. If yes, I put it in the first post!
     
  4. power7

    power7 Notebook Evangelist

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    Yes, actually measured all 3. 90W shows up as disconnected.
     
  5. zsero

    zsero Notebook Deity

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    Thanks, first post updated.
     
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