Did I get the right capacitor?

Discussion in 'The Projects Forum' started by judoGTI, Jan 12, 2010.

  1. judoGTI

    Thread Starter Member

    May 26, 2005
    25
    0
    Hello - I'm trying to complete this circuit and am having a hard time sourcing the right capacitor. It needs to be a .1uF

    At first I got a ceramic capacitor, but then read you should not use ceramic ones for analog circuits. So then I got a few of these. The bin said they were .1 mfd (I assume that meant micro farad which = .1uF?) But looking at the top it seems to say either ".1K100" OR "1K100" and the dot indicates the polarity (+)? Or do I need to run to radioshack and get a cap that is more barrel shaped that has obvious polarity (electrolytic I believe they are called)

    Thanks!

    I'm trying to build one of these:
    http://www.instructables.com/id/The-Most-Useless-Machine/

    [​IMG]

    Here is the circuit
    [​IMG]
     
  2. k7elp60

    Senior Member

    Nov 4, 2008
    478
    69
    You have the right capacitor. I believe the K is the tolerance, + or - 10%
    So the capacitance is 0.1uf(MF) + or - .01uf. The voltage rating is 100V which if okey. It is a film dielectric capacitor so as long as the working voltage is greater than what you using it will be fine.
     
  3. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    For that purpose, ceramic would be fine.

    By the way, the .01 uF cap, C2, is important for stability.
     
  4. judoGTI

    Thread Starter Member

    May 26, 2005
    25
    0
    Thank you both. I'll wire it up tonight!

    When you say C2 is needed for stability, Im not sure what you mean by stability? Of the signal?

    I'm also a little confused as to why pin 5,2,1 &6 are connected and between pins 2 & 5 with the connection of the 1 pin it also goes to ground there. It seems like an odd place for it, but my knowledge as to how this works just yet (beyond the basic switching of power) is still a little shaky.

    Thanks for the help with C1 cap!
     
  5. t06afre

    AAC Fanatic!

    May 11, 2009
    5,939
    1,222
    By the way. You do not have any decoupling cap. You should use the spare .1uF ceramic ones for this purpose. Put it close to pin 8 and the other end to GND
     
  6. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Google "lm555" and get a data sheet. It will explain how the IC works and what the pins do.
     
Loading...