capacitors 20% inaccurate for 555 calculation

Discussion in 'General Electronics Chat' started by lotusmoon, Jun 16, 2013.

  1. lotusmoon

    Thread Starter Member

    Jun 14, 2013
    203
    4
    I am making a circuit with a 555 timer and calculating the frequency. But have been told that capacitors are 20% inaccurate. So my 100Hz might be anywhere between 80Hz and 120Hz is there a way round this? is it possible to buy accurate capacitors?
     
  2. Evil Lurker

    Member

    Aug 25, 2011
    117
    23
    Yes it is possible to get higher accuracy. You just have to use caps such as film or ceramic with tighter tolerances, less temperature drift, and measure each capacitor's capacitance and cherry pick the best of the lot.
     
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  3. Shagas

    Active Member

    May 13, 2013
    802
    74
    Any clever way of measuring capacitance without a capacitance meter?
    My guess is probably not , but I thought I'd ask anyway :)
     
  4. Markd77

    Senior Member

    Sep 7, 2009
    2,803
    594
    Put it in a 555 timer circuit and measure the frequency (or other oscillator circuit).
     
  5. #12

    Expert

    Nov 30, 2010
    16,250
    6,746
    The usual way is to use a variable resistor to adjust the timing. Cheap, available, effective.
     
  6. lotusmoon

    Thread Starter Member

    Jun 14, 2013
    203
    4
    Thank you all for all your great ideas.
    I am new to electronics, but another way round this is there something like a digital screen that will display the frequencies from a variable circuit?
     
  7. MrChips

    Moderator

    Oct 2, 2009
    12,418
    3,355
    Build a frequency meter.
    Also, many DMM have frequency function.
     
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