What are Capacitors used for?

Comments

• Whit Posts: 4,191

  2007-05-23 00:23 edited 2007-05-23 00:23

  Try a google search of wiki + capacitors and you will get http://en.wikipedia.org/wiki/Capacitor
  
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  Whit+
• Chris Savage Parallax Engineering Posts: 14,406

  2007-05-23 04:32 edited 2007-05-23 04:32

  This thread is being moved from the BASIC Stamp Forum to the Sandbox Forum.
  
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  Chris Savage
  Parallax Tech Support
• metron9 Posts: 1,100

  2007-05-23 16:35 edited 2007-05-23 16:35

  Basically they work like a tiny battery (the small ones) but they can be charged very fast. They are used to smooth voltage drops for DC power. For example you have a motor that needs 20 amps to start but runs at 5 amps. A starting capacitor can be charged to provide the extra current needed for a small amount of time.
  
  Capacitors can hold high voltage, and then be discharged very fast to make big sparks. Some capacitors are very expensive and can hold lots of energy, it's their ability to charge and discharge at very high rates that makes them different from a typical battery.
  
  Look up FARAD , capacitors are rated in units of charge capacity based on the FARAD.
  
  Be careful when working with even small ones as they can explode (if connected wrong) as some have plus and minus connections and connected backwards or too high of voltage can make them explode. The ceramic types can easily put your eye out at close range so ware safety glasses when experimenting. Shocks are not the only hazard when working with electronic devices. Smoke and fire can be made with 9V batteries as well.
  
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  Re-arrange what's inside the box then...
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• Paul Baker Posts: 6,351

  2007-05-23 18:43 edited 2007-05-23 18:43

  Here's a slightly more electronics view on capacitors (and inductors):
  
  Capacitors oppose changes in voltage between thier two pins, they like the voltage to remain constant. If it's not constant it will store charge across it's plates when the voltage increases (ie take away some of the current in an attempt to suppress the voltage) or will dump charge from its plates when the voltage decreases (ie add some current in an attempt to "prop up" the voltage). A capacitor isn't concerned with the current flowing and will make fluctuations in the current in its attempt to hold the voltage steady. The larger the value of the capacitor, the more effect it's effort has on the circuit.
  
  Inductors oppose changes in current running through it, they like the current to remain constant. If it's not constant it will store charge in an electromagnetic field when the current increases (ie take away some of the current in attempt to suppress the current) or will dump charge from its field when the current decreases (ie add some current in an attempt to "prop up" the current). An inductor isn't concerned with the voltage across it and will make fluctuations in the voltage in its attempt to hold the current steady. The larger the value of the inductor, the more effect it's effort has on the circuit.
  
  So you can see while inductors and capacitors are both devices capable of storing charge, the way they use that charge and it's effect on the circuit is different.
  
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  Paul Baker
  Propeller Applications Engineer
  
  Parallax, Inc.
• cameron Posts: 33

  2007-05-24 12:58 edited 2007-05-24 12:58

  Hey Paul,
  
  Thanks that is just what I wanted to know thanks, I couldn't understand why you connected them right next to the chip's pins but it must be to keep the voltage straight on 5V.
  
  Thank you.
• Paul Baker Posts: 6,351

  2007-05-24 19:03 edited 2007-05-24 19:03

  Thats exactly why they are included, and they are placed so close to minimize the resistance between the capacitor and the supply pin because the resistance has an adverse effect on the capacitors ability to keep the line at 5V.
  
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  Paul Baker
  Propeller Applications Engineer
  
  Parallax, Inc.