How to choose the right capacitor

Discussion in 'The Projects Forum' started by Jassper, Oct 17, 2008.

  1. Jassper

    Thread Starter Active Member

    Sep 24, 2008
    84
    1
    I know this is some basic stuff here, but for the life of me I can't seem to grasp the knowledge.

    Basically, how do I know what type and value of a capacitor to use. I know what a cap does and how it works, just I can't grasp how to figure the value needed of any given situation.

    For example.
    I have a 5 volt DC motor that I need to run. Amp draw is about 60mA.
    I want to be sure that 1) there is enough voltage to start the motor instantly, and 2) prevent a backlash from the coil of the motor when it stops. I know this can be done by using a cap across the +/- of the motor but I don't like just guessing at the value/type I need.

    I have seen Mylar caps on these motors, i have seen Ceramic caps on these motors, and I have seen electrolyte caps on these motors, so does the type really matter?
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Capacitors across the motor are usually there to act as snubbers for sparks from the brushes. A small mylar or ceramic cap in the range of .01 to .1 is probably enough.
     
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