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Thread: Problems with multiple pots on analog inputs ??????

  1. #1
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    Default Problems with multiple pots on analog inputs ??????

    Hi All,

    Am i going to have problems when using multiple pots wired into the Analog inputs?

    Looking at my sketch below, i've basically wired 4 x 10K pots across the +5volt and ground rails, then feeding the wipers into the Analog inputs.
    In this case, the overall pot resistance would only be 2.5K, is this going to be a problem? and is adjusting 1 pot going to actually slightly adjust the other pot values too?

    Will the addition of diodes in series with the pots isolate them from affecting eachother?

    In the grand scheme, i'd be using 10 x pots or upto 16 pots.
    P1030197.JPG

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    Should work just fine, the diodes are not needed. 10K is a nice high pot value, the currents are too low to affect each other.

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    Hi Oldmarty

    I agree with erco.

    I have wired two sets of joysticks - 4 10k pots into a 18m2 with no problems.

    Bill
    "It always seems imposible until it's done" Nelson Mandela.

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    Thanks guys, i was getting concerned, because one application will use 16 x 10k pots, which wil equate to a 625ohm resistor across the 5v and ground rails, maybe i should 'up' all my pots to 25 or 50k to prevent the rail getting pulled on too much.

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    Quote Originally Posted by erco View Post
    Should work just fine, the diodes are not needed. 10K is a nice high pot value, the currents are too low to affect each other.
    but it's not really a 10k value, it will look like 2.5k to the power rail and perhpas limited range to the analog inputs???

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    Cool

    Assuming your 5v supply won't draw down with 2.5 k [5/2500=.002 amperes] - no problem and the voltage from pot wipers is 0-5v...

    [I just posted at 11:14 PM local and it came up 00:01 on forum! ]
    Last edited by premelec; 11-01-2017 at 08:03. Reason: time!

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    We are aware of the server time discrepancy and will be seeking to resolve the issue.

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    Sixteen 10K pots would draw a total of 8 mA constantly at 5V. That's chump change compared to robots with multiple servos pulling 500 mA each. Unless you're powering from AAA cells or a 9V battery then you're fine.

    But yes, higher value pots would draw proportionally less. Sixteen 50K pots would draw 8/5=1.6 mA total.

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    In a battery-powered project where current consumption was crucial, I would power each individual potentiometer from a Picaxe output port, which I would scan sequentially. Of course the readings from each AD port should be synchronized with the corresponding output port.
    Last edited by fernando_g; 11-01-2017 at 19:55.
    "Will design analog circuitry for Beer."

  10. #10
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    You could put 1K between 5V and the pots as lowest value.

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