circuit symbols - alliance for telecommunications · 3 ieee graphical symbols ansi/ieee std...

Circuit symbols

Presented by Mick Maytum

March 19-21, 2013San Ramon, CA

PROTECTIONENGINEERSGROUP CONFERENCE

DISTINGUISHED LECTURERPROGRAM

Surge Protection 101 - Part 2

2

Summary

All protection engineers read and interpret circuit diagrams. This operation is often a bilingual one as U.S. symbols are often mixed with international ones. Further, manufacturers often use unique symbols of their own. This discussion covers the origins of various circuit symbols, how they are drawn (correctly) and the major differences among them.





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IEEE Graphical Symbols

ANSI/IEEE Std 315-1975 - IEEE Graphic Symbols for Electrical and Electronics Diagrams (ANSI Y32) is often referenced for component symbols. ANSI/IEEE Std 315A-1986, a supplement extends the range of symbols and is based on IEC 617 (Now the online database standard IEC

60617)





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IEC Graphical Symbols

The IEC 60617 is a subscription database of graphical symbols for use in electrotechnical diagrams.





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Symbol PresentationExample PNP Transistor

IEC 60617

IEEE 315

Visio

Shareware Visio

JEDEC

Thick-BaseCentre join





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Symbol DrawingIEC 60617 - Introduction

The relative proportions of the symbols should be retained when they are reduced or enlarged.

Symbols may be turned or mirror-imaged if their meaning will not be changed thereby.

If the symbol for a particular device or design cannot be found in the standard it should be possible to produce it by an appropriate combination of the published symbols (primitives).

For clarity, symbols are usually shown with connecting lines. If the symbol for a particular device or design cannot be found in the

standard it should be possible to produce it by an appropriate combination of the published symbols e.g. adding “hooked” line for non-linearity.





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Symbol DrawingIEC 60617 - computer-aided draughting - 1

To facilitate the use of the IEC 60617 symbols with a computer-aided system: The symbols have been designed so that they can be used on a grid system with a

modulus M. The modulus used in this standard, 2.5 mm, is not mandatory; Connecting lines to a symbol coincide with the grid lines and end at grid line

intersections; The sides of rectangles and the diameter of circles have been made multiples of 2

M. For smaller symbols also dimensions equal to 1.5 M, 1 M and 0.5 M have been

used; A distance of at least 2 M (5 mm) has been provided between connecting lines to

meet the requirements of ISO-Standard 3098/1-1974: Technical Drawings –Lettering, for a minimum character height of 2.5 mm.

It is an additional requirement of computer-aided systems that each symbol should have a reference point located at a grid intersection (shown as a star).





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Symbol DrawingIEC 60617 - computer-aided draughting - 2

Stars are reference points





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Symbol DrawingIEC 60617 - computer-aided draughting – 3: PNP Transistor

Drawing on a grid maintains the connectivity and relative dimensions no matter what the final size.





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Symbol DrawingOther stuff

ISO 3098/1 Technical drawings - LetteringPreferred heights h of Capital letters are in root 2 ratios:2.5 mm - 3.5 mm - 5 mm - 7 mm - 10 mm - 14 mm - 20 mm

ISO 3461-2 General principle of creating graphic symbolsPreferred module M size with rate of root 2 is:2.5 mm - 3.5 mm - 5 mm - 7 mm - 10 mm - 14 mm - 20 mm

ISO 128 Line thickness0.25 mm - 0.35 mm - 0.5 mm - 0.7 mm - 1 mm - 1.4 mm - 2 mmRatio of thick to thin shall not be less than 2:1





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Pre-drawn Symbols

The quickest and most convenience way of producing circuit diagrams is to use software with an electronic symbol library.

General purpose drawing programs e.g. Visio CAD programs e.g. AutoCAD Dedicated electronic circuit drawing programs Spice or other modelling programs

Points to check Are the available symbols compliant to symbol drawing standards? If needed, can you make symbols from primitive shapes? How can the drawings be exported to other programs?





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Manufactures don’t help

Here are the symbols used for a bidirectional thyristor overvoltage protectors from various manufactures.





4MANUFACTURERS

1MANUFACTURER

3MANUFACTURERS

1MANUFACTURER

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IEEE SPDC has started making pre-drawn symbol sets





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IEEE SPDC pre-drawn symbol set example





Switch SPST Capacitor Resistor

Varistor Avalanche Breakdown Diode

Inductor

circuit symbols - alliance for telecommunications · 3 ieee graphical symbols ansi/ieee std...

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