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Topic: What do you make of this??? (Read 512 times) previous topic - next topic

Nick Gammon

(back in the days when Pluto was a planet)

Whatever DID happen to Pluto? It was the Klingons, wasn't it?

Runaway Pancake

If you use the CMOS 555, the 7555, then you won't need that cap there at all.
There are 0.1uF tantalums, I have some, but I haven't seen any polarised values less than that.
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Jack Christensen

I'm cool with the pluto thing but I thought, there I go thinking again, that tantalum and electrolytic caps used the arc and straight line symbol and other caps used two straight line symbol.  That is what has me wondering. Here we have and arc and straight line with no polarity.  I can throw a 0.47 cap in and see what happens.  I'm sure nothing will self destruct but I have never seen this symbol for a non-electrolytic cap before.

Yes, I've seen that convention too, not sure it was recently though. There are regional differences as well.
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Apr 27, 2012, 03:35 am Last Edit: Apr 27, 2012, 12:27 pm by pwillard Reason: 1
Regional differences are correct.   EU (and a lot of the rest of other places too) used 2 parallel lines to indicate a non-polarized capacitors.  In the USA and nearby places it is common to use the line and arc even for non-polarized types... making the only difference between polarized types and the non-polarized types the "+" symbol.  

My feeling is that the arc side of the symbol has its roots from the days of very early radio schematics and normally indicated, for convenience only, the side of the capacitor that was closer to GND potential and not a particular characteristic of the part itself.  Japan even uses yet another symbol for capacitors.  

Old conventions take a long time to change and  the influences like Popular Electronics, American Radio Relay League and other American style publications on the American "old farts",  still persists today.  Elektor, Everyday Practical Electronics and Silicon Chip, for example are publications that perpetuate the more understandable "---||---" parallel plates symbols and are more sensible because there really is no need to show polarity on a non-polarized capacitor.  The "+" symbol is really 'good enough'.  

In really olden days, capacitors also came in big metal cylindrical cases and it was believed that a 1 FARAD capacitor (a value now seen in super caps) would need to be a big as a delivery truck.  Some things change... some things stay the same.

For example, I never could get the hang of EIA-logic gate schematic symbols style versus JEDEC style.  I learned JEDEC style and my brain would not let me change.


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