Help selecting base materials of capacitors

Discussion in 'General Electronics Chat' started by Rbeckett, Jun 29, 2012.

  1. Rbeckett

    Thread Starter Member

    Sep 3, 2010
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    I see multiple different basic materials available in capacitors, is there some selection criteria that demands certain types of base materials over others? For instance could I use an electrolytic in place of a tantalum or metalized polyester as long as respect is paid to correct capacity, operating voltages and polarity. Do different base materials have some other affect on the capacitor other than size and capacitance such as Tantalum being a required component versus a ceramic or vice versa. I see many different base materials but they are all rated and sorted by Farads and volts with no other mention of a particular need for a specific material or why. Thanks for the help understanding this.
    Bob
     
  2. bertus

    Administrator

    Apr 5, 2008
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  3. #12

    Expert

    Nov 30, 2010
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    I can tell you that I looked up Sprague "Orange Drop" capacitors because I had to deal with an audio nut. I found that the energy loss in the dielectric (dielectric absorbtion) was the factor that led to the "reputation" of these caps as "best" for audio purposes.

    These are a "polyfilm" dielectric. I got the information from a pamphlet published by the manufacturer. You can dig for information and study for hours to get a clear picture of which cap is best for each purpose.
     
  4. MrChips

    Moderator

    Oct 2, 2009
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    A tantalum is an electrolytic... another type of electrolytic.
    There are aluminum electrolytic capacitors,
    there are tantalum electrolytic capacitors.
     
  5. Rbeckett

    Thread Starter Member

    Sep 3, 2010
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    Mr Bertus,
    After reading the link you posted I feel safe in assuming for non critical applications such as a home hobbyist would engage in that if you have a cap of the proper voltage and capacity you can use them all interchangeably to a certain extent. The differring base materials all represent some differences in basic properties like freq, leakage and indictance, but for the most part are essentially intechangeable if they will physically fit in the alloted space. I really appreciate the link because it explained what I intuitively felt, but could not justify with just anecdotal information.
    Bob

    The underlying reason for the question is to conserve money while building my bench stock of common parts. Buying all manner of caps is essentially a waste and the funds can be applied to other more meaningfull investments in other neccessary components.
     
    Last edited: Jun 29, 2012
  6. MrChips

    Moderator

    Oct 2, 2009
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    For most applications, non-polar ceramic caps under 1μF will be fine.

    For critical timing applications such as filters, tone controls, 555 timers and monostables use polystyrene capacitors.

    For polarized electrolytic capacitors 1μF and greater, aluminum capacitors will be less expensive than tantalum electrolytics and will work fine in most cases.
     
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  7. Rbeckett

    Thread Starter Member

    Sep 3, 2010
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    Thanks Mr Chips,
    I was trying to avoid buying Mica, Polyester, polystyrene, electrolytic, ceramic and all the other base material designs if not absolutely neccessary. I currently have some misc caps, and full selections of electrolytic and ceramics already. No need to continue with caps till the rest of my bench stock begins to fill out in the thin areas first. Slowly but surely I am building a bench stock that will allow me to just sit down and build with very little delay due to waiting for a common part to arrive. I'm getting there a little at a time. Thanks for all the help guys and gals!!!
    Bob
     
  8. #12

    Expert

    Nov 30, 2010
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    Don't forget that you can get a lot of stock for bench experiments by butchering old TV's and such. I got a lot of good tantalums out of old hard drives, and they are expensive! I got a lot of polyfilm caps out of old TV's. I wouldn't buy those except for audio jobs like guitar amplifiers. Polystyrene caps are very good capacitors but you rarely use them. For instance, 555 timer applications usually need a capacitor so large that you can't buy them in polystyrene. Ceramic caps are fairly cheap and fairly good. Definitely prefer them for anything small enough that you don't need to use electrolytics, but you need to learn the codes for tolerance ratings. Some of them are rated like, +80% to -20%.

    Just hoping to be helpful.
     
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  9. takao21203

    Distinguished Member

    Apr 28, 2012
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    Yes I have one bag PCBs here from old VCRs, good for obscure component values, but not really worth the labour to unsolder all the parts.

    So I simply keep the PCBs, and remove components, when I need them.

    For ceramic caps, power resistors, I use kits from eBay, not expensive, as well I have some bags with polyester caps here.

    Crystals I sometimes unsolder, but no need, I have many new ones as well.

    Most switching regulators I have built can work using aluminium electrolytics, but new technology chips with high frequency need tantalum or ceramic caps.

    I tested for some circuits recently, using tantalum or electrolytic, makes zero difference for input current (= efficiency). Noise/ripple is not a concern for my purposes.
     
  10. Rbeckett

    Thread Starter Member

    Sep 3, 2010
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    #12,
    Can you direct or recomend a site that will fully discuss the numbering and tolerance issues you mentioned? I am definately learning to be a sponge when it comes to electronics, datasheets, and specs and find that the more I look around the less I really have a clue about. Bertus has been a Godsend with the links and resources he consistently offers, without that kind of info I will continue to be just plain ignorent of the hows and why's of how anything really works and why. Thanks a bunch.
    Wheelchair Bob
     
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