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  1. #21
    Senior Member
    Join Date
    Oct 2009
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    Western/Northern New York
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    1,016
    Quote Originally Posted by AxxelH View Post

    One question, does anyone care to speculate whether the max amperage rating matters? I only had a 5v 1a wall wart at hand (vs 5v 2a original). For a normal USB charging situation I wouldn't worry about this, all the lower amperage would mean is a slower charge, but not sure that applies here. In practice the duet controller is charging now, but I can always order a PSM11R-050 if it actually matters.
    This is a good question, but I think that only an inspection of the schematic and charging IC would yield the answers, and they aren't available (to my knowledge).

    I worked as an EE at a company that would use OEM power supplies in our products (Infant Products, like swings, baby monitors, etc). Thinking practically, a company would not be including a power supply 2x the size needed for no reason. In general you don't want to exceed 80% capacity, so in this case, the design could require up to 1.6A. But, thinking that the supplies from the OEM's would be standard 1A, 2A would lead me to think that it's more than 80% of the 1A. To have a supplier build a custom (say 1.5A) would be more expensive than just using a 2A.

    I am thinking that the (designed) draw is over 0.8A and probably less than 1.6A. But you can measure either by opening and disconnecting, or, if you use a device like a Kill-a-watt and measure VA, that would give you the DC power being drawn (when you divide VA by 5v).

    You could also look to see if the voltage is drooping under load, or if the power brick is getting abnormally warm.

    One final thought - we think of it as a charging cradle, but is it possible that it draws more power when the controller is being used in the cradle?


    Sorry for all this random information You could probably just but the right supply

    Jim

  2. #22
    Junior Member
    Join Date
    Dec 2016
    Posts
    28
    Quote Originally Posted by Redrum View Post
    Thinking practically, a company would not be including a power supply 2x the size needed for no reason. In general you don't want to exceed 80% capacity, so in this case, the design could require up to 1.6A. But, thinking that the supplies from the OEM's would be standard 1A, 2A would lead me to think that it's more than 80% of the 1A. To have a supplier build a custom (say 1.5A) would be more expensive than just using a 2A.
    This is an excellent point, thanks for making it. As much as I am concerned that I won't be as successful with the soldering iron a second time (I'm a software guy), this was enough to convince me to eBay the "right" supply. Nothing about the design of the cradle (hardwired wall wart? really?) leads me to believe that Logitech was really thinking about flexibility or servicing, and you're absolutely right it was probably built to a very specific design and price.

    Nothing got hot (or even warm really) when charging at 1a, but I can believe that may not be indicative of max load. Better safe, etc.

    Thanks for the comment, now I get to see if I can replicate my earlier success with the right part.

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