confusion on diode polarity

rabiticide · 2008-12-30T16:25:36+00:00

I'm trying to make a basic circuit with a diode. Had it not beenmarked "cathode/anode" I would have not been confused - I would'vejust had the electrons follow the arrow. But the arrow points awayfrom the anode and towards the cathode, and this is the opposite ofwhat I'd expect.What does "cathode" and "anode" mean on a diode? To have the electronsflow with the arrow my "anode" will be a higher voltage than my"cathode" which is the opposite of what I would have thought. How am Ibeing confused?

Dec 30, 2008 24 Replies

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Jasen Betts 17 years ago

to paraphrase:

the problem with this is that only the PV array with the higher output current will contribute to the charging process.

i think in real life it depends on which parameter the arrays are most closely matched.

Real arrays behave like they have non-trivial internal resistance, so they if they procude similar voltages they can be paralleled and will share the load quite well.

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Eeyore 17 years ago

An 'accident of fate'. It was a 50/50 chance. Doesn't seem to cause any trouble though unless you're dealing with device physics.

Graham

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John Fields 17 years ago

I think that would be true in the parallel case, where the PV with the highest voltage would cut the other one off by back-biasing its diode. In the series case, the current into the charger would be limited to the current available from the lower-current PV, but the voltage into it would be the sum of the PVs\' voltages, making the power into the charger greater than that available from either PV alone, I think.

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John Fields 17 years ago

Not true, since the current into the charger will be limited to what the _lower_ current PV array can supply. However, the _voltage_ into the charger will be the sum of the array output voltages, allowing the battery to be charged for a longer time until the charger\'s input voltage falls to the point where current can no longer be forced into the battery. JF

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John Fields 17 years ago

Not really, since one of Murphy\'s law states something like: "If you have a 50/50 chance of being right, 90% of the time you\'ll be wrong." JF

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