How to differentiate Tantalum and Aluminum Electrolytic cap in one schematic?

Discussion in 'General Electronics Chat' started by sanmu13579, Apr 12, 2013.

  1. sanmu13579

    Thread Starter New Member

    Apr 12, 2013
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    Hello,

    Assumed that there are both Tantalum Electrolytic capacitor and Aluminum Electrolytic capacitor in the same schematic, how to differentiate them? Normally we use the symbol (attached file 1) to represent general polarized capacitor, but if there are two types of polarized capacitor, how to make the reader easily differentiate them?

    In practice, do we use another symbol for Tantalum Electrolytic capacitor (maybe this one? attached file 2), and use the general symbol (attached file 1) for Aluminum Electrolytic capacitor?

    Thanks.
     
  2. #12

    Expert

    Nov 30, 2010
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    I'm not aware of a tantalum symbol, so I just write, "tant" when that's what I mean. Like this:
     
  3. crutschow

    Expert

    Mar 14, 2008
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    Normally the capacitor type and voltage rating is stated on the parts list. You don't typically build a circuit just from the schematic.
     
  4. WBahn

    Moderator

    Mar 31, 2012
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    Unless you believe it is critical to have a visual distinction between the two, try to minimize the number of different symbols you use. If you do use a second symbol, be sure there is some kind of a legend on the schematic saying which is which. Otherwise, people will be confused and wonder if one of the symbols is being used to represent a completely different type of component.

    As crutscholw says, you typically have a BOM (bill of materials) to accompany a schematic. If you want the BOM to be more-or-less optional (perhaps you expect the schematic to normally be available but not the BOM for one reason or another), then you need to be sure that all critical information is annotated on the schematic. I've seen schematics that had ALL of the BOM information, including Digi-Key part numbers, right on the schematic next to each part. It made for a cluttered schematic (downside) but was very handy to have a single resource with all the information on it. The best of both worlds is when the BOM is presented in a table that located at the bottom or the side of the schematic. Of course, this only works for relatively small circuits.
     
  5. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    I've only seen two capacitor symbols: polarized and non-polarized.

    Material used for the construction gets noted over in the bill of materials. May possibly be a note on the schematic but that is the exception.
     
  6. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    #12, nice chematic - the reference to a waterbed just made me laugh and brought back memories that were fun and awkward while being totally void of electronics. Not what I was expecting! Thanks.
     
  7. #12

    Expert

    Nov 30, 2010
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    I designed and built that in 1978 when water beds still existed.
    Right now, it is working as a space heater controller in my bedroom.
     
  8. Padapolis

    New Member

    Feb 21, 2013
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    OK, but what if the designer of a circuit leaves out that one particular bit of information about the capacitors? Other than reading tea leaves, and consulting the daily star charts, is there a way to determine what type of caps are used?

    Here is an example:
    Here is a circuit schematic with a bill of materials.
    http://www.pira.cz/enbar.htm
    And here is a YouTube video of this circuit in action.
    http://www.youtube.com/watch?v=KGfe9ldM9HU

    In the video it looks to me like there are two diffrent types of capacitors on the board. I hate to think that flipping a coin because of a lack of a standardized symbol is a replacement for years of experience.
     
  9. takao21203

    Distinguished Member

    Apr 28, 2012
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    If there is no extra info, about any capacitor will do.
     
  10. #12

    Expert

    Nov 30, 2010
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    If there is no specification for what kind of capacitor it is, you assume aluminum electrolytic. After that, you are allowed to use your knowledge of electronics to decide whether you want a tantalum cap in that position.
     
  11. WBahn

    Moderator

    Mar 31, 2012
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    So should there be a standardized symbol for mica caps? How about one for polyester caps? Polypropylene? Ceramic? What about a standardized symbol for the different tempcos, which are sometimes extremely important for proper circuit operation? What if the designer leaves off the voltage rating? Should we standardize that information into the symbol, as well? And that's just the caps!

    If the design leaves important information out of the schematic/BOM, then they aren't being a very good designer and what are the chances they would have used the correct symbol to begin with?

    The only reason we have polarized and non-polarized symbols is because it is important for the person using the schematic to built the material to know that this particular cap has to go into the circuit a particular way -- in other words, the schematic needs to capture relevant construction information.
     
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