Outer Limits 4x4 Board

Because I am raiding a complete disco loom for various bits and pieces, I have a few fairly chunky diodes at my disposal. Now I have never used a diode in auto wiring before.

Correct me if I am wrong, but I think I can make use of one of them in this scenario:

I have an air con switch.
I have a temp sensor for an electric fan.

I want the fan to come on whenever the air con is switched on.
I want the fan to come on when the temp sensor kicks in.
I DON'T want the air con to switch on when the temp sensor kicks in.

If I didn't have a diode sitting there I would probably have used an extra relay to achieve my goal, but I think I can just put a diode in line:

A/C switch sends +12V to A/C compressor and, via a diode, to the thermo fan relay.

Temp sensor sends +12V to the thermo fan relay.

Diode prevents temp sensor from activating the A/C.

Is this right?

Jason

ps if Scott calls me a n00b I will sick the whole forum onto him

Yep. White stripe is the "output" side. Current flows from input to output. (electrons flow the other way, but that's a historical issue)

Paul

chimpboy wrote:ps if Scott calls me a n00b I will sick the whole forum onto him

Hmmm. Thinking, thinking...

me3@neuralfibre.com wrote:Yep. White stripe is the "output" side. Current flows from input to output. (electrons flow the other way, but that's a historical issue)

Paul

electrons don't flow - holes flow - in the direction of conventional current.

and yes you can use a diode to achieve that goal.

dumbdunce wrote:

me3@neuralfibre.com wrote:Yep. White stripe is the "output" side. Current flows from input to output. (electrons flow the other way, but that's a historical issue)

Paul

electrons don't flow - holes flow - in the direction of conventional current.

and yes you can use a diode to achieve that goal.

how do holes flow?

Electrons are a physical thing, and they are what "moves".

a "hole" is the absence of an electron.

Shadow wrote:

dumbdunce wrote:

me3@neuralfibre.com wrote:Yep. White stripe is the "output" side. Current flows from input to output. (electrons flow the other way, but that's a historical issue)

Paul

electrons don't flow - holes flow - in the direction of conventional current.

and yes you can use a diode to achieve that goal.

how do holes flow?

Electrons are a physical thing, and they are what "moves".

a "hole" is the absence of an electron.

Urrgh - this could get very messy.
It also depends on the overall charge in relation to a true ground state. If there is an excess or lack of valance electrons.
I'm happy to leave both statements stand, it all depends on what was being taught at the time, and the subatomic physics could get messy.

(Hijak) I did see a statement the other day in a Greenie mag that said new High Voltage DC was being considered as a transmission medium for wind due to lower losses than AC. That was a new one to me, I thought Telsla thoroughyl tromped Edison there. Looks like these things can be more complicated then commonly accpepted.

Paul

Current flow and electron flow are kind of metaphors anyway aren't they? Conceptually, you could say "charge flows" and it's workable.

At the subatomic level, correct me if I'm wrong, but electrons do not exactly have a precise location and to say that they "flow" is not technically right; they jump around.

chimpboy wrote:Current flow and electron flow are kind of metaphors anyway aren't they? Conceptually, you could say "charge flows" and it's workable.

At the subatomic level, correct me if I'm wrong, but electrons do not exactly have a precise location and to say that they "flow" is not technically right; they jump around.

Does this mean I shouldn't tell people my vacuum resovoir is "A tank full of vacuum"?

You are correct with your statement Mr Schrodinger.

Paul

chimpboy wrote: At the subatomic level, correct me if I'm wrong, but electrons do not exactly have a precise location and to say that they "flow" is not technically right; they jump around.

who knows - hands up who has ever seen an electron?

me3@neuralfibre.com wrote:

Shadow wrote:

dumbdunce wrote:

me3@neuralfibre.com wrote:Yep. White stripe is the "output" side. Current flows from input to output. (electrons flow the other way, but that's a historical issue)

Paul

electrons don't flow - holes flow - in the direction of conventional current.

and yes you can use a diode to achieve that goal.

how do holes flow?

Electrons are a physical thing, and they are what "moves".

a "hole" is the absence of an electron.

Urrgh - this could get very messy.
It also depends on the overall charge in relation to a true ground state. If there is an excess or lack of valance electrons.
I'm happy to leave both statements stand, it all depends on what was being taught at the time, and the subatomic physics could get messy.

(Hijak) I did see a statement the other day in a Greenie mag that said new High Voltage DC was being considered as a transmission medium for wind due to lower losses than AC. That was a new one to me, I thought Telsla thoroughyl tromped Edison there. Looks like these things can be more complicated then commonly accpepted.

Paul

HVDC is already in use in Aus, Basslink is HVDC
i think one reason for its use is zero impedance on the cable, and also you can use a smaller cable for the same true power due to the skinning effect of high current AC

It's not just weirdo lefties.

Where the wind blows

Jul 26th 2007
From The Economist print edition

A grandiose plan to link Europe's electricity grids may recast wind power from its current role as a walk-on extra to being the star of the show

by Stephen Jeffrey



PLUG in your toaster—or your television or your vacuum cleaner—and the electricity that surges through it is an alternating current. The question of whether the world would be powered by direct current (DC), in which electrons flow in one direction around a circuit, or by alternating current (AC), in which they jiggle back and forth, was decided in the 1880s. Thomas Edison backed DC. George Westinghouse backed AC. Westinghouse won.

The reason was that over the short distances spanned by early power grids, AC transmission suffers lower losses than DC. It thus became the industry standard. Some people, however, question that standard because over long distances high-voltage DC lines suffer lower losses than AC. Not only does that make them better in their own right, but employing them would allow electricity grids to be restructured in ways that would make wind power more attractive. That would reduce the need for new conventional (and polluting) power stations.


AC/DC/PC

Wind power has two problems. You don't always get it where you want it and you don't always get it when you want it. According to Jürgen Schmid, the head of ISET, an alternative-energy institute at the University of Kassel, in Germany, continent-wide power distribution systems in a place like Europe would deal with both of these points.

The question of where the wind is blowing would no longer matter because it is almost always blowing somewhere. If it were windy in Spain but not in Ireland, current would flow in one direction. On a blustery day in the Emerald Isle it would flow in the other.

Dealing with when the wind blows is a subtler issue. In this context, an important part of Dr Schmid's continental grid is the branch to Norway. It is not that Norway is a huge consumer. Rather, the country is well supplied with hydroelectric plants. These are one of the few ways (but not the only way, see article) that energy from transient sources like the wind can be stored in grid-filling quantities. The power is used to pump water up into the reservoirs that feed the hydroelectric turbines. That way it is on tap when needed. The capacity of Norway's reservoirs is so large, according to Dr Schmid, that should the wind drop all over Europe—which does happen on rare occasions—the hydro plants could spring into action and fill in the gap for up to four weeks.

Put like this, a Europe-wide grid seems an obvious idea. That it has not yet been built is because AC power lines would lose too much power over such large distances. Hence the renewed interest in DC.

Westinghouse won the battle of the currents in the 1880s because it is easier to transform the voltage of an AC current than of a DC current. High voltage is the best way to transmit power (the higher the voltage, the smaller the loss), but high voltage is not usually what the user wants. Power is therefore transmitted along high-tension AC lines and then “stepped downâ€

chimpboy wrote:Current flow and electron flow are kind of metaphors anyway aren't they? Conceptually, you could say "charge flows" and it's workable.

At the subatomic level, correct me if I'm wrong, but electrons do not exactly have a precise location and to say that they "flow" is not technically right; they jump around.

A hole is the lack of an electron, or a positively charged atom.

Electrons dont flow from one end of a cable to another, rather, an electron jumps from one atom to the next, which makes the atom it jumped to have an excess of electrons, which means it can release an electron ontop the next atom etc.

A negatively charged atom has a hole, or an electron missing, the hole cant move, but it can be filled by a an electron from a neighbouring atom. Like a bucket brigade arangement. The empty bucket doesnt move, the water just moves around it.

That was what i was taught in my electronic engineering degree.

ausoops wrote:

me3@neuralfibre.com wrote:

Shadow wrote:

dumbdunce wrote:

me3@neuralfibre.com wrote:Yep. White stripe is the "output" side. Current flows from input to output. (electrons flow the other way, but that's a historical issue)

Paul

electrons don't flow - holes flow - in the direction of conventional current.

and yes you can use a diode to achieve that goal.

how do holes flow?

Electrons are a physical thing, and they are what "moves".

a "hole" is the absence of an electron.

Urrgh - this could get very messy.
It also depends on the overall charge in relation to a true ground state. If there is an excess or lack of valance electrons.
I'm happy to leave both statements stand, it all depends on what was being taught at the time, and the subatomic physics could get messy.

(Hijak) I did see a statement the other day in a Greenie mag that said new High Voltage DC was being considered as a transmission medium for wind due to lower losses than AC. That was a new one to me, I thought Telsla thoroughyl tromped Edison there. Looks like these things can be more complicated then commonly accpepted.

Paul

HVDC is already in use in Aus, Basslink is HVDC
i think one reason for its use is zero impedance on the cable, and also you can use a smaller cable for the same true power due to the skinning effect of high current AC

believe there is also a dc link from vic to sa, will check when i'm at tafe next week. dc transmission is more effecient that ac, but only at high voltages and generally very long transmission lines.

they have dc transmission in russia, very long lines connecting huge power stations to cities located far apart, at 1MV (1 million volts). another important considerations is dc links can be used to link systems of different frequencies, say 50Hz system to a 60 Hz system.

ac transmission is much better overall as it is cheaper and easier to change voltage levels ie transformers, 3 phase motors are cheaper, smaller than 1 phase and definately dc motors, instrumentation is cheaper and easier ie voltage and current transformers, most translines are cheaper with ac than dc (see above exceptions), ac generators are much better (cheaper, smaller, effecient) and more.

the conversion stations, ac recitied into dc and dc inverted into ac are very expensive.


as a side note i fail to see any real link between wind farms and dc tranmission. yes, i suppose you could feed the wind tower power directly into battery banks, but they generate ac electricity, so need to convert to dc to charge batteries, then would need a converter station somewhere (at site but this talks about near the load ie cities) back to ac for people to use.

Bluey wrote:

ausoops wrote:

me3@neuralfibre.com wrote:

Shadow wrote:

dumbdunce wrote: electrons don't flow - holes flow - in the direction of conventional current.

and yes you can use a diode to achieve that goal.

how do holes flow?

Electrons are a physical thing, and they are what "moves".

a "hole" is the absence of an electron.

Urrgh - this could get very messy.
It also depends on the overall charge in relation to a true ground state. If there is an excess or lack of valance electrons.
I'm happy to leave both statements stand, it all depends on what was being taught at the time, and the subatomic physics could get messy.

(Hijak) I did see a statement the other day in a Greenie mag that said new High Voltage DC was being considered as a transmission medium for wind due to lower losses than AC. That was a new one to me, I thought Telsla thoroughyl tromped Edison there. Looks like these things can be more complicated then commonly accpepted.

Paul

HVDC is already in use in Aus, Basslink is HVDC
i think one reason for its use is zero impedance on the cable, and also you can use a smaller cable for the same true power due to the skinning effect of high current AC

believe there is also a dc link from vic to sa, will check when i'm at tafe next week. dc transmission is more effecient that ac, but only at high voltages and generally very long transmission lines.

they have dc transmission in russia, very long lines connecting huge power stations to cities located far apart, at 1MV (1 million volts). another important considerations is dc links can be used to link systems of different frequencies, say 50Hz system to a 60 Hz system.

ac transmission is much better overall as it is cheaper and easier to change voltage levels ie transformers, 3 phase motors are cheaper, smaller than 1 phase and definately dc motors, instrumentation is cheaper and easier ie voltage and current transformers, most translines are cheaper with ac than dc (see above exceptions), ac generators are much better (cheaper, smaller, effecient) and more.

the conversion stations, ac recitied into dc and dc inverted into ac are very expensive.


as a side note i fail to see any real link between wind farms and dc tranmission. yes, i suppose you could feed the wind tower power directly into battery banks, but they generate ac electricity, so need to convert to dc to charge batteries, then would need a converter station somewhere (at site but this talks about near the load ie cities) back to ac for people to use.

the link between wind farms and DC links is the massive transmission saving from DC links, which means, you can have wind farms in norway and iraq linked by a massive DC link, when the wind blows in norway, iraq is powered by norway, when its blowing in iraq, norway gets its power from iraq.

Its not saying wind farms work better on DC, its saying wind farms become more functional when you can have a huge dispersion of generators, as wind is generally always blowing somewhere.

Oh dear what did I start........

Shadow wrote:

Bluey wrote:

ausoops wrote:

me3@neuralfibre.com wrote:

Shadow wrote: how do holes flow?

Electrons are a physical thing, and they are what "moves".

a "hole" is the absence of an electron.

Urrgh - this could get very messy.
It also depends on the overall charge in relation to a true ground state. If there is an excess or lack of valance electrons.
I'm happy to leave both statements stand, it all depends on what was being taught at the time, and the subatomic physics could get messy.

(Hijak) I did see a statement the other day in a Greenie mag that said new High Voltage DC was being considered as a transmission medium for wind due to lower losses than AC. That was a new one to me, I thought Telsla thoroughyl tromped Edison there. Looks like these things can be more complicated then commonly accpepted.

Paul

HVDC is already in use in Aus, Basslink is HVDC
i think one reason for its use is zero impedance on the cable, and also you can use a smaller cable for the same true power due to the skinning effect of high current AC

believe there is also a dc link from vic to sa, will check when i'm at tafe next week. dc transmission is more effecient that ac, but only at high voltages and generally very long transmission lines.

they have dc transmission in russia, very long lines connecting huge power stations to cities located far apart, at 1MV (1 million volts). another important considerations is dc links can be used to link systems of different frequencies, say 50Hz system to a 60 Hz system.

ac transmission is much better overall as it is cheaper and easier to change voltage levels ie transformers, 3 phase motors are cheaper, smaller than 1 phase and definately dc motors, instrumentation is cheaper and easier ie voltage and current transformers, most translines are cheaper with ac than dc (see above exceptions), ac generators are much better (cheaper, smaller, effecient) and more.

the conversion stations, ac recitied into dc and dc inverted into ac are very expensive.


as a side note i fail to see any real link between wind farms and dc tranmission. yes, i suppose you could feed the wind tower power directly into battery banks, but they generate ac electricity, so need to convert to dc to charge batteries, then would need a converter station somewhere (at site but this talks about near the load ie cities) back to ac for people to use.

the link between wind farms and DC links is the massive transmission saving from DC links, which means, you can have wind farms in norway and iraq linked by a massive DC link, when the wind blows in norway, iraq is powered by norway, when its blowing in iraq, norway gets its power from iraq.

Its not saying wind farms work better on DC, its saying wind farms become more functional when you can have a huge dispersion of generators, as wind is generally always blowing somewhere.

ok, so i didn't read the whole document posted above. still doubt its cost effectiveness, the current range of wind turbines are only 3MW each, you would need the whole of the country covered in them. slight exageration, but i hope you get my point.

Bluey wrote:

Shadow wrote:

Bluey wrote:

ausoops wrote:

me3@neuralfibre.com wrote: Urrgh - this could get very messy.
It also depends on the overall charge in relation to a true ground state. If there is an excess or lack of valance electrons.
I'm happy to leave both statements stand, it all depends on what was being taught at the time, and the subatomic physics could get messy.

(Hijak) I did see a statement the other day in a Greenie mag that said new High Voltage DC was being considered as a transmission medium for wind due to lower losses than AC. That was a new one to me, I thought Telsla thoroughyl tromped Edison there. Looks like these things can be more complicated then commonly accpepted.

Paul

HVDC is already in use in Aus, Basslink is HVDC
i think one reason for its use is zero impedance on the cable, and also you can use a smaller cable for the same true power due to the skinning effect of high current AC

believe there is also a dc link from vic to sa, will check when i'm at tafe next week. dc transmission is more effecient that ac, but only at high voltages and generally very long transmission lines.

they have dc transmission in russia, very long lines connecting huge power stations to cities located far apart, at 1MV (1 million volts). another important considerations is dc links can be used to link systems of different frequencies, say 50Hz system to a 60 Hz system.

ac transmission is much better overall as it is cheaper and easier to change voltage levels ie transformers, 3 phase motors are cheaper, smaller than 1 phase and definately dc motors, instrumentation is cheaper and easier ie voltage and current transformers, most translines are cheaper with ac than dc (see above exceptions), ac generators are much better (cheaper, smaller, effecient) and more.

the conversion stations, ac recitied into dc and dc inverted into ac are very expensive.


as a side note i fail to see any real link between wind farms and dc tranmission. yes, i suppose you could feed the wind tower power directly into battery banks, but they generate ac electricity, so need to convert to dc to charge batteries, then would need a converter station somewhere (at site but this talks about near the load ie cities) back to ac for people to use.

the link between wind farms and DC links is the massive transmission saving from DC links, which means, you can have wind farms in norway and iraq linked by a massive DC link, when the wind blows in norway, iraq is powered by norway, when its blowing in iraq, norway gets its power from iraq.

Its not saying wind farms work better on DC, its saying wind farms become more functional when you can have a huge dispersion of generators, as wind is generally always blowing somewhere.

ok, so i didn't read the whole document posted above. still doubt its cost effectiveness, the current range of wind turbines are only 3MW each, you would need the whole of the country covered in them. slight exageration, but i hope you get my point.

not the point really

a DC grid would make them alot more practical. How efficient they are is kind of irrelavent.

i have worked at 2 wind farms so far in aus, and will be working on another soon (next year) and both were put in where the ac transmission was nearby. not for that reason, the reason obviously was because of the wind. why go to the expense and trouble to put in a new dc transline when the ac network is close by.

ac network has distributiopn transformers everywhere to feed into the customers, dc will need converter stations all over. as for transferring power from one country to another, well that would be hugely costly to install, to pay off landowners who aren't going to get any of the power, and cheaper and easier to find a windy area in your own country, all the political ramifications or other forms power generation

the (normal so far in world) uses of dc transmissions lines are:
under water connection like bass link
connecting systems of different frequencies
connecting big generators (eg nuclear) that are remote (hugely) to where the customers are, like russia, or simply long distances (believe there is a dc link from canada to usa, gotta check tho)

The basic point was just that when you are looking at a REALLY big grid, like a continent-wide grid, you are looking at DC not AC.

Wind and solar both get better as grids get bigger.

yeah, i understand what you and shadow are saying

but
there would be a huge amount of political crap in putting a wind farm in one state but supply to another (just think of a windfarm in vic but the power ends up in qld only, people wouldn't stand for it), could you imagine putting a wind farm in one country but it feeds a completely different country? norway and iraq were one example given

yes, the dc link can be more effecient for very long lines, but you can't tee off it like ac to feed local areas without putting in converter stations, and they are expensive. windfarms and solar stations will become viable as they're respective technology improves, not because of the transmission type

Bluey wrote:yeah, i understand what you and shadow are saying

but
there would be a huge amount of political crap in putting a wind farm in one state but supply to another (just think of a windfarm in vic but the power ends up in qld only, people wouldn't stand for it), could you imagine putting a wind farm in one country but it feeds a completely different country? norway and iraq were one example given

yes, the dc link can be more effecient for very long lines, but you can't tee off it like ac to feed local areas without putting in converter stations, and they are expensive. windfarms and solar stations will become viable as they're respective technology improves, not because of the transmission type

i dont think theyd give a shit aslong as qld was paying for the power.

its aboput supply and demand, if qld mneeds more and can pay, then have it.