confusion on diode polarity

[rabiticide]

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?

 

[Tom Biasi]

"rabiticide" <rabiticide@gmail.com> wrote in message
news:c6166a49-a3c0-46c5-884c-3fdeb578bcc9@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

 

[John Larkin]

On Tue, 30 Dec 2008 08:25:36 -0800 (PST), rabiticide
<rabiticide@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

 

[Rich Webb]

On Tue, 30 Dec 2008 08:25:36 -0800 (PST), rabiticide
<rabiticide@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

 

[Peter Bennett]

On Tue, 30 Dec 2008 08:25:36 -0800 (PST), rabiticide
<rabiticide@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

 

[rabiticide]

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)---------------------------------
_________

?

 

[Rich Webb]

On Tue, 30 Dec 2008 09:47:06 -0800 (PST), rabiticide
<rabiticide@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

 

[rabiticide]

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)---------------------------------
_________

?

 

[John Fields]

On Tue, 30 Dec 2008 09:47:06 -0800 (PST), rabiticide
<rabiticide@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

 

[rabiticide]

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

 

[Bob Penoyer]

On Tue, 30 Dec 2008 08:25:36 -0800 (PST), rabiticide
<rabiticide@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?

It is an unfortunate fact that Benjamin Franklin guessed wrong when he
declared the direction of electric current flow. Before anyone figured
out that he was wrong, the scientific world had adopted Franklin's
"convention."

Everyone knows that--at least in metallic conductors--it is the
negatively charged electrons that flow, but we say that current flows
from positive to negative because we have agreed to use Franklin's
convention.

All the world's electrical engineers are taught to use conventional
current flow. Unfortunately, a lot of technician-level courses and
books teach electron flow. This leads to a lot of confusion for people
coming out of such courses or reading such books.

If you change your way of thinking to assume current flows from
positive to negative, then you will find it much easier to interpret
schematic symbols and schematic diagrams. Electrical schematic symbols
assume conventional current flow.

For example, think of the diode symbol as a funnel that lets the
current flow into it, but the bar across one end blocks current from
flowing the other way.

Also, transistors will make more sense since, using an NPN transistor,
a current entering the base will follow the arrow and flow into the
emitter, thus turning the transistor on.

Learn to think in terms of conventional current, not electron flow,
and your understanding will be enhanced.

 

[Eeyore]

rabiticide 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.

No, the current follows the arrow.

Graham

 

[Jamie]

rabiticide 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?
If I remember my history, Anode and Cathode is a derivative of

Anions and Cations when speaking of Ions.

Anions ions are atoms that have gained electrons, making them
more negatively charged, "Anode"

Cations ions are atoms that have lost electrons making them
more like vacuums, if you would, looking for electrons to fill it
back up. (basically). or simply saying, it's just has less electrons
making it more positive or less negative, depending on how you look
at it.

So, to translate this to electronics as in a diode..
Nodes are the end points, hence the Cations = Cathode,
Anions = Anode..

If you have a higher charge of Electrons on the Cathode
side of the diode (- voltage), than what is on the anode, a
flow will take place in the attempt to fill the void of electrons
on the anode side.. Or, if you want to look at it this way, the
Anode side will act as a vacuums sucking electrons from the cathode
side.
Or as the Navy explains it, Electrons flow (-) to (+). In short
what they mean is, Since there are more electrons on one side (-), its
going to flow towards the (+) side because of fewer electrons on the
(+) side and there for, it's like attempting to equalize the two..

Simply put, the bigger guy goes first. Of course, in this process
current is produced which is like a back wash. so one could say that
current flows (+) to (-)..

So in short!.
If the (+) voltage on the anode side is higher than the (+)
voltage on the cathode side, you'll have a current flow.

THe Line of the DIODE indicates the connection point for the
Cathode.
If you have more (+) voltage on the anode side (&gt than on
the cathode side (|), current will flow.

And with that I'll have another shot of wine! ;/

http://webpages.charter.net/jamie_5"

 

[Paul E. Schoen]

"John Fields" <jfields@austininstruments.com> wrote in message
news:jmpkl4tiej4avd7492j3vbs985h2ofnk5s@4ax.com...

On Tue, 30 Dec 2008 09:47:06 -0800 (PST), rabiticide
rabiticide@gmail.com> wrote:

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?


+--[-PV1+]---[DIODE>]---+
| | +----------+ ____
+--[-PV2+]---[DIODE>]---+--|+IN +OUT|----+-O O-+
| | | |+ |
| | CHARGER | [BAT] [LOAD]
| | | | |
+--------------------------|-IN -OUT|----+------+
+----------+

The problem with this is that only the PV array with the higher output will
contribute to the charging process. It is more efficient to use two
chargers, the outputs of which will be closely matched, and they can be
designed for parallel output without additional steering diodes. The
chargers should be boost converters (assuming Vbat > Vpv), and they can be
designed so that they extract the maximum power from the photocells by
monitoring input voltage and current.

Paul

 

[Paul E. Schoen]

"rabiticide" <rabiticide@gmail.com> wrote in message
news:c6166a49-a3c0-46c5-884c-3fdeb578bcc9@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?

Conventional current flow allows for a more intuitive concept of having the
highest positive voltage represent the source of current, and then there
are voltage drops around the circuit for each element as current flows
through them. The fact is that the more negative point has the most
electrons, but we have chosen their polarity to be negative. It is easier
to follow conventional current flow through the arrows of semiconductors
(when forward biased), and show a higher (more positive) voltage at the
anode as compared to the cathode.

Paul

 

[Jamie]

rabiticide 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.

You are referring to the anode of the diode, the side that does not
have the line(band) on the body.

The (+) lead of the panel connects on that side and the
(+) voltage from the panel will come out the other side of the diode
which does have the line (band) on it.

Hope that was simply enough.

P.s.
you'll give ~ 0.6 voltage loss through the diode.

http://webpages.charter.net/jamie_5"

 

[John Fields]

On Tue, 30 Dec 2008 18:26:24 -0500, "Paul E. Schoen" <pstech@smart.net>
wrote:

"John Fields" <jfields@austininstruments.com> wrote in message
news:jmpkl4tiej4avd7492j3vbs985h2ofnk5s@4ax.com...
On Tue, 30 Dec 2008 09:47:06 -0800 (PST), rabiticide
rabiticide@gmail.com> wrote:

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?


+--[-PV1+]---[DIODE>]---+
| | +----------+ ____
+--[-PV2+]---[DIODE>]---+--|+IN +OUT|----+-O O-+
| | | |+ |
| | CHARGER | [BAT] [LOAD]
| | | | |
+--------------------------|-IN -OUT|----+------+
+----------+

The problem with this is that only the PV array with the higher output will
contribute to the charging process. It is more efficient to use two
chargers, the outputs of which will be closely matched, and they can be
designed for parallel output without additional steering diodes. The
chargers should be boost converters (assuming Vbat > Vpv), and they can be
designed so that they extract the maximum power from the photocells by
monitoring input voltage and current.

---
Good point but, since two chargers are twice as expensive as one and as
the OP stated that his lights suffered only in winter, I'd recommend:


+----------+ ____
+--[PV2+]---|+IN +OUT|----+-O O-+
| | | |+ |
| | CHARGER | [BAT] [LOAD]
| | | | |
+--[+PV1]---|-IN -OUT|----+------+
+----------+

Which will get rid of all of the diodes and, if the charger is a buck
switcher,

Well...

Now we venture into the land of conjecture...

JF

 

[Paul E. Schoen]

"John Fields" <jfields@austininstruments.com> wrote in message
news:grdll4dnr0mv5jof76qqcvrt7hg6gec9oa@4ax.com...

Good point but, since two chargers are twice as expensive as one and as
the OP stated that his lights suffered only in winter, I'd recommend:


+----------+ ____
+--[PV2+]---|+IN +OUT|----+-O O-+
| | | |+ |
| | CHARGER | [BAT] [LOAD]
| | | | |
+--[+PV1]---|-IN -OUT|----+------+
+----------+

Which will get rid of all of the diodes and, if the charger is a buck
switcher,

Well...

Now we venture into the land of conjecture...

If both solar panels are about equally insolated (amount of light applied),
then this, or the other approach with both in parallel, will be OK. The
problem is that the current from the panel (or cell) with the least amount
of light will limit how much the others can supply. A persistent shadow can
be a real show-stopper. But I have not had much experience with PV, so
maybe it is not as much problem as I think.

Paul

 

[krw]

In article <grdll4dnr0mv5jof76qqcvrt7hg6gec9oa@4ax.com>,
jfields@austininstruments.com says...

On Tue, 30 Dec 2008 18:26:24 -0500, "Paul E. Schoen" <pstech@smart.net
wrote:


"John Fields" <jfields@austininstruments.com> wrote in message
news:jmpkl4tiej4avd7492j3vbs985h2ofnk5s@4ax.com...
On Tue, 30 Dec 2008 09:47:06 -0800 (PST), rabiticide
rabiticide@gmail.com> wrote:

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?


+--[-PV1+]---[DIODE>]---+
| | +----------+ ____
+--[-PV2+]---[DIODE>]---+--|+IN +OUT|----+-O O-+
| | | |+ |
| | CHARGER | [BAT] [LOAD]
| | | | |
+--------------------------|-IN -OUT|----+------+
+----------+

The problem with this is that only the PV array with the higher output will
contribute to the charging process. It is more efficient to use two
chargers, the outputs of which will be closely matched, and they can be
designed for parallel output without additional steering diodes. The
chargers should be boost converters (assuming Vbat > Vpv), and they can be
designed so that they extract the maximum power from the photocells by
monitoring input voltage and current.

---
Good point but, since two chargers are twice as expensive as one and as
the OP stated that his lights suffered only in winter, I'd recommend:


+----------+ ____
+--[PV2+]---|+IN +OUT|----+-O O-+
| | | |+ |
| | CHARGER | [BAT] [LOAD]
| | | | |
+--[+PV1]---|-IN -OUT|----+------+
+----------+

Wouldn't that presume the PVs are identical? As I read it, he
wanted to augment the built in PV panel with an external. It would
seem difficult to match them.

Which will get rid of all of the diodes and, if the charger is a buck
switcher,

Well...

Now we venture into the land of conjecture...

What's wrong with that? It is the favorite game of the Usenet
community. ;-)

--
Keith

 

[rabiticide]

okay I'm going to try them in parallel with the schottky diodes and if
that does not work ... series connection will be okay? I don't know
what a "buck switcher" is... it's a cheap set-up from Kmart which
charges 3, AA NiMH batteries...