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basics | confusion on diode polarity
There are 26 messages in this thread.
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confusion on diode polarity - rabiticide - 2008-12-30 11:25:00
I'm trying to make a basic circuit with a diode. Had it not been marked "cathode/anode" I would have not been confused - I would've just had the electrons follow the arrow. But the arrow points away from the anode and towards the cathode, and this is the opposite of what I'd expect. What does "cathode" and "anode" mean on a diode? To have the electrons flow 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 I being confused?
Re: confusion on diode polarity - Tom Biasi - 2008-12-30 11:37:00
"rabiticide" <r...@gmail.com> wrote in message news:c...@s1g2000prg.googlegroups.com... > I'm trying to make a basic circuit with a diode. Had it not been > marked "cathode/anode" I would have not been confused - I would've > just had the electrons follow the arrow. But the arrow points away > from the anode and towards the cathode, and this is the opposite of > what I'd expect. > > What does "cathode" and "anode" mean on a diode? To have the electrons > flow 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 I > being confused? Cathode and anode mean the same to a diode as they do to everything else in electronics, you can research that. The electrons do not "follow" the direction of the arrow for a forward conducting diode. The electrons will flow against the arrow. I understand your confusion. Look up electron flow and conventional current. To conduct the anode needs to be more positive than the cathode. The cathode is marked with a stripe. The anode is the arrow. Tom
Re: confusion on diode polarity - John Larkin - 2008-12-30 11:49:00
On Tue, 30 Dec 2008 08:25:36 -0800 (PST), rabiticide <r...@gmail.com> wrote: >I'm trying to make a basic circuit with a diode. Had it not been >marked "cathode/anode" I would have not been confused - I would've >just had the electrons follow the arrow. But the arrow points away >from the anode and towards the cathode, and this is the opposite of >what I'd expect. > >What does "cathode" and "anode" mean on a diode? To have the electrons >flow 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 I >being confused? Current flows from positive to negative, in the direction of the arrow. John
Re: confusion on diode polarity - Rich Webb - 2008-12-30 11:52:00
On Tue, 30 Dec 2008 08:25:36 -0800 (PST), rabiticide <r...@gmail.com> wrote: >I'm trying to make a basic circuit with a diode. Had it not been >marked "cathode/anode" I would have not been confused - I would've >just had the electrons follow the arrow. But the arrow points away >from the anode and towards the cathode, and this is the opposite of >what I'd expect. > >What does "cathode" and "anode" mean on a diode? To have the electrons >flow 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 I >being confused? Brings back memories of the good ol' days at Nuc School. The enlisted students were taught "electron flow" and the officers "conventional flow." What was HGR thinking?! Conventional current is positive to negative. Electrons don't really flow, they sort of ooze slowly along at the blazing speed of inches per minute. And, in some conductors, the charge carriers aren't electrons at all! Don't worry about it. Current is + to - and goes in the direction of the "arrow" on the diode. -- Rich Webb Norfolk, VA
rectifying photovoltaic - rabiticide - 2008-12-30 12:30:00
Okay, so I'm trying to hook two solar cells in parallel and I don't want current to try and go reversi through it. So I take the red wire from the photovoltaic cell (+), hook it to the tail of the arrow, and connect the head of the arrow to the electronics I want to power, right? _________ | | | |----(+ RED)-----(----->|-----)------------ | P.V. | | | (charging circuit) (mirror image with another PV cell and diode) | |----( - BLACK)--------------------------------- _________ ?
Re: confusion on diode polarity - Peter Bennett - 2008-12-30 12:31:00
On Tue, 30 Dec 2008 08:25:36 -0800 (PST), rabiticide <r...@gmail.com> wrote: >I'm trying to make a basic circuit with a diode. Had it not been >marked "cathode/anode" I would have not been confused - I would've >just had the electrons follow the arrow. But the arrow points away >from the anode and towards the cathode, and this is the opposite of >what I'd expect. > >What does "cathode" and "anode" mean on a diode? To have the electrons >flow 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 I >being confused? The arrows in transistor and diode symbols point in the direction of "conventional" (positive) current flow - opposite to the direction of electron flow, so the arrow points to the more negative terminal of the diode if you wish the diode to conduct. Note that Zener diodes are used in a reverse breakdown mode - in that case, the arrow points to the more positive terminal. -- Peter Bennett, VE7CEI peterbb4 (at) interchange.ubc.ca GPS and NMEA info: http://vancouver-webpages.com/peter Vancouver Power Squadron: http://vancouver.powersquadron.ca
Re: rectifying photovoltaic - rabiticide - 2008-12-30 12:47:00
I had to correct this because my spaces were removed. The periods (........) are just place holders. On Dec 30, 9:30 am, rabiticide <rabitic...@gmail.com> wrote: > Okay, so I'm trying to hook two solar cells in parallel and I don't > want current to try and go reversi through it. So I take the red wire > from the photovoltaic cell (+), hook it to the tail of the arrow, and > connect the head of the arrow to the electronics I want to power, > right? > > _________ > | | > | |----(+ RED)-----(----->|-----)------------ > | P.V. | > | |.........................................................(charging circuit).....(mirror image with another PV cell and diode) > | | > | |----( - BLACK)--------------------------------- > _________ > > ?
Re: rectifying photovoltaic - Rich Webb - 2008-12-30 13:32:00
On Tue, 30 Dec 2008 09:47:06 -0800 (PST), rabiticide <r...@gmail.com> wrote: >I had to correct this because my spaces were removed. The periods >(........) are just place holders. > >On Dec 30, 9:30 am, rabiticide <rabitic...@gmail.com> wrote: >> Okay, so I'm trying to hook two solar cells in parallel and I don't >> want current to try and go reversi through it. So I take the red wire >> from the photovoltaic cell (+), hook it to the tail of the arrow, and >> connect the head of the arrow to the electronics I want to power, >> right? >> >> _________ >> | | >> | |----(+ RED)-----(----->|-----)------------ >> | P.V. | >> | |.........................................................(charging circuit).....(mirror image with another PV cell and diode) >> | | >> | |----( - BLACK)--------------------------------- >> _________ >> >> ? Yes, with the caveat that you'll need to be sure to use diodes with the proper ratings. Probably Schottky types, since PV systems don't have a lot of spare power to waste on diode drops. -- Rich Webb Norfolk, VA
Re: rectifying photovoltaic - John Fields - 2008-12-30 13:50:00
On Tue, 30 Dec 2008 09:47:06 -0800 (PST), rabiticide <r...@gmail.com> wrote: >I had to correct this because my spaces were removed. The periods >(........) are just place holders. > >On Dec 30, 9:30 am, rabiticide <rabitic...@gmail.com> wrote: >> Okay, so I'm trying to hook two solar cells in parallel and I don't >> want current to try and go reversi through it. So I take the red wire >> from the photovoltaic cell (+), hook it to the tail of the arrow, and >> connect the head of the arrow to the electronics I want to power, >> right? >> >> _________ >> | | >> | |----(+ RED)-----(----->|-----)------------ >> | P.V. | >> | |.........................................................(charging circuit).....(mirror image with another PV cell and diode) >> | | >> | |----( - BLACK)--------------------------------- >> _________ >> >> ? --- View in Courier, and please don't top post: +--[-PV1+]---[DIODE>]---+ | | +----------+ ____ +--[-PV2+]---[DIODE>]---+--|+IN +OUT|----+-O O-+ | | | |+ | | | CHARGER | [BAT] [LOAD] | | | | | +--------------------------|-IN -OUT|----+------+ +----------+ JF
Re: rectifying photovoltaic - rabiticide - 2008-12-30 15:04:00
Thanks. I will order up some schottky types which are not carried at radio shack... Top posting was unintentional, probably a result of my changing the subject line. I am attempting to bolster the charge on my walkway lights which work fine in the summer, but do not get enough juice in the winter months. I will let you know how it goes. Again, thank you. rK