500k pot

Discussion in 'The Projects Forum' started by ale2121, Apr 21, 2009.

  1. ale2121

    Thread Starter Active Member

    Mar 20, 2009
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    hi, i have a bunch of potentiometers, but not the values I need. can i add regular resistors in line with a 100k pot to get close? or, should i just use a pot that's way bigger, like a 1meg pot?
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,635
    2,342
    Hello,

    That depends on he application.
    Can you post a circuit?
    What is the use of the pot at this circuit?

    Greetings,
    Bertus
     
  3. ale2121

    Thread Starter Active Member

    Mar 20, 2009
    71
    0
    i can't find it online. it's the stepped tone generator from the forest mims 555 book. i believe these two 500k pots control the frequency of each of the 555s in the 556.
     
  4. bertus

    Administrator

    Apr 5, 2008
    15,635
    2,342
    Hello,

    You may use the 1M pot, the range will be twice as large.
    For the 555 is this no problem.

    Greetings,
    Bertus
     
  5. -SK-

    Member

    Apr 14, 2009
    25
    0
    If you add other resistors, such as 400k in series with the 100k pot, you would only get a 5th of the range (400k-500k). Check the book to see if it gives more info on the range you need. If the range only needs to be a portion of that 500k, you could get away with a 100k and other resistors, you might lose some functionality of the circuit.
     
  6. Wendy

    Moderator

    Mar 24, 2008
    20,764
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    You can do what you're suggesting, but the linearity will suffer greatly. Overall, I would say it is not a problem.
     
  7. ale2121

    Thread Starter Active Member

    Mar 20, 2009
    71
    0
    cool, thanks everyone.
     
  8. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    If you need to decrease R1 from 500k to 100k, you can compensate by increasing C1 from 0.01uF to 0.047uF.

    If you need to decrease R2 from 500k to 100k, you can compensate by increasing C2 from 0.1uF to 0.47uF.

    Forrest M. Mims III's circuits are copyrighted material, and as such cannot be posted here without his written permission.
     
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