I thought that rewording the title of a previous post as this one might result in a better response. I imagine that there are a lot of characteristics of conductors to consider including the type, amount, and consistency of their makeup.

 

I think you are thinking about it the wrong way. It is much more general than that. THe difference between an insulator and conductor, a better and poorer conductor, and a better and poorer insulator is pretty much the same.

It has to do with the bandgap of the material.
Band gap - Wikipedia, the free encyclopedia

But the most important information for you is found in the pictures and key sentences here about the difference between conductors, insulators, and semiconductors.
Valence band - Wikipedia, the free encyclopedia
Conduction band - Wikipedia, the free encyclopedia
Electronic band structure - Wikipedia, the free encyclopedia

BACKGROUND:
Here it is very simplified and in a nutshell to help you visualize...electrons orbiting a nucleus and an atom can exist in only certain states orbits around the atom. THey cannot exist in between, but they can jump between orbits. As the orbit gets farther from the nucleas, the attraction that the nucleas has on the electron becomes less and less. Therefore, as the orbits get farther and farther from the nucleas, the electrons needs to gain less energy to jump to a farther orbit until it eventually just breaks free of the nucleas. The orbits where the electron are free is called the conduction band. In this band the electrons are free to flow around to the conduction band of nearby atoms. The orbits were the electrons are held is called the valence band. The "distance" (really the difference in energy for an electron to jump) between the farthest valence band and the closest conduction band is called the "band gap" or "band gap energy".

Take a while to absorb that if you've never heard that before.

CONDUCTORS:
Okay! Now, in metals there is an "overlap" of the conduction band and valence band. What does this mean? It means it takes no energy for electrons to move between valence and conduction band. So the materials conduct any electron can move to the conduction band whenever it wants to and be free to move around (and be part of the electrical current).

INSULATORS:
Insulators on the other hand have a very large "distance" between the conduction band and valence band. Another way to put it, is that the band gap energy is very large. THe electrons need huge amounts of energy to jump from the valence band to the conduction band to escape the hold of the nucleas and be part of the electrical current. You probably know about how every material, even insulators, become conductors at high enough voltages. THis is, here, the reason why. Current is the number of electrons flowing while voltage is the energy that each electron has. As you increase the voltage, the electrons just keeps getting more and more energy. Eventually it has enough to jump the band gap (from the valence band into the conduction band) no matter how large it is.

SEMICONDUCTORS:
Semiconductors are the third. They have no overlap in the band gap, unlike conductors. But unlike insulators the don't have a very large band gap. The electrons only need a little "push" of energy to get them to jump from the valence band to the conduction band. So, this means by applying a small amount of energy to the electron(for example, in the form of voltage/current directly, or to produce an electric field which givens energy to the electrons indirectly) , you get turn it from an insulator into a conductor. And as a conductor, it can carry a much larger amount of energy/current than the energy that was needed to change it from an insulator to semiconductor.

So really, in the eyes of physics there is no clear-cut difference between an insulator, conductor, and semiconductor. They are all operating on the same sweeping general laws, just to varying degrees. Hope this helps!

PS. I noticed in your last post you were also curious about transparency, etc. The bandgap energy also controls the following:
-whether the material can be used for a solar panel, how efficient it is, and what wavelengths will work on it.
-to what wavelengths the material is transparent or opaque to
-whether the material can be used as a radiation source, it's efficiency, and what radiation it will generate (ir. IR, UV, visible light, X-rays)

I also THINK it affects the index of refraction and reflectivity (both in the wavelength of EM radiation being used as well as the angle of incidence of the radiation...each wavelength has a certain angle that will produce near 100% reflection.) I believe it also affects how fast different wavelengths of EM radiation travel through the material (which affects what wavelengths of EMR a lens will work for, and how thicker or thiner the lens needs to be to do the same job as a lens of a different material).

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Tanaka Sensei (avatar) says: Please spell it "ridiculous" correctly! Not "rediculous". ^^

 

So unfortunately, it might be possible that it is impossible to have a transparent conductor.

Current does tend to take the path of least resistance. But it does "leak out". For example, a large flat square with two tiny contacts at opposite corners. THe current will for the most part flow in a straight line, but it does kind of spread out around the middle before converging to get to the opposite contact. And you will probably find exponentially less current flowing through the metal as you move farther away from this line.

Same deal goes for current flowing a flat copper sheet, and then a flat sheet with a block of copper sitting in the middle. Small amounts would flow through the copper block, but very little. Even less if it was farther away from "the line" between the contacts on the copper sheet.

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Tanaka Sensei (avatar) says: Please spell it "ridiculous" correctly! Not "rediculous". ^^

 

You seem to have a lot of information. Do you know of any specific conductors that I can buy in a sheet larger than about 2 feet squared that have resistive properties? I would like to use such a sheet as a variable resistor that resists electricity according to how a probe is dragged across the sheet.

 

I think somebody else on the forum in another thread a while back brought up carbon sheets (like carbon paper) and is a flat resistive material with documented resistances. CAn't say whether or not it would work for whatever application you are looking for.

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Tanaka Sensei (avatar) says: Please spell it "ridiculous" correctly! Not "rediculous". ^^

 

Carbon paper might work, but I would prefer something more durable… Are there simple models of the electrical properties of conductors that have an inconsistent composition of more than one semi-finished material, like a geometric model of electron flow?

 

If what you are looking for is a large hard slab of resistive material, you're out of luck. You'd have to approach a resistor manufacturer and custom order large slab-like resistors that are made of some resistive ceramic or resistive or alloy which would be very very expensive and they wouldn't even consider you because you aren't ordering in massive quantities. One of the problems is that the more material you have, the smaller the resistance and the harder it gets to measure. Another problem is you need the resistive material exposed (when it is normally coated for protection in resistors) and they tend to be materials that aren't so durable.

Huh? If you are looking to map the distribution of electron flow through something, that is something essentially "no one" really cares about. And anyone that did would be using electromagnetics simulation software to do it. The rarity of software like that would probably make it very expensive too. How would you even pin point where something is on a single resistive sheet?

I'm going to try now to convince you to consider alternative methods:

1. Did you think of your physical circuit implementation to detect something on a resistive sheet? The only way I can come up with is to line the edges of the sheet with contacts and then measure the resistance between every single opposing pair of contacts and then choose opposing X-pair with the lowest resistance and the Y-pair with the lowest resistance and call that the position of the playing piece. A few problems arise with this method. First of all, it is IMPOSSIBLE to detect the position of more than one piece because there is just too much coupling between the outputs and the positions of the pieces. This pretty much puts the nail in the coffin for a gaming board.

2. Playing pieces tend to be much smaller than the board itself (by definition almost), and since current distributions decrease exponentially away from the line of sight between the two contacts that are conducting current, this means that for the most part, the height of a playing piece does not contribute very much to current flow. At the same time, it also means that you are not forcing current to flow across the piece and the patch of board it is in contact with. Current is still free to leak flow around the piece on the board and both of these effects means the change in resistance produced is even less.

3. Also by definition, one board tends to have a large number of playing pieces. Recall that resistors of largely different values tend to dominate each other in different ways when connected in series or in parallel. A parallel connection would be similar to the playing piece and the patch of board it is in contact with, and a series connection would be this patch/piece and the REST of the board. This means that either way, you cannot have a large difference in "effective resistance" (taking into account how current will now flow through the entire volume of the playing piece and how current will also flow on the board around the piece) between board and piece. That's somewhat of a problem seeing as how you have many different playing pieces. Dividing the board's resistance up equally among the playing pieces doesn't work because as soon as you split the piece/patch resistor pairs, you get the board-only paths dominating the resistance circuit. More smaller footprints for each piece also means more leakage current around the piece compared to one large piece of the same combined footprint. It just doesn't work.

From your previous thread, it seems you are just going about this the wrong way and seem unopen to alternative methods. Lots of people come onto the forums with great difficulty finding parts or designing things because they are going about things the wrong way and continue to have difficulty because chose an approach that isn't possible with current materials or technology and refuse to change. Things for such applications do exist. Like capacitive touch, or really any array of anything- resistive, capacitive laser, etc. They also have the advantage of durability especially capacitive since it works through materials unlike resistance which needs direct contact.

But I think the most important change that is needed is for you to use an array of elements rather than a single array (plus it will be a lot easier to get a bunch of smaller parts than one really big part). Well, that's not entirely true. Your own camera suggestion from your previous thread probably counts as single element unless you count the CCD pixels. But that is probably the best way if you have too many elements in your array to build. If only to be able to detect the position of more than one piece. If you really want a "simple model" one good guess is that it is a gaussian distribution away from the line between the two contact points, even then this does not change the arguments made above.

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Tanaka Sensei (avatar) says: Please spell it "ridiculous" correctly! Not "rediculous". ^^

 

A rubber or PVC ESD workbench mat is probably your best option.

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I do not answer private messages asking for help because no one else can: benefit from advice I may give or correct me if I'm wrong.

Please ask on the open forum if you have a question and I'll be happy to help, if I know the answer.

 

A fire investigator might be interested in the range of resistances of slabs of material – though these slabs of material might not be made for the purpose of measuring resistances. I’m curious about what this range might be.

 

How so, do you think?

 

If I understand correctly, there is a relationship between an amount of resistance offered by a material and an amount of heat released. I believe that this is why some resistors might have special fireproof features. It might be important for a fire investigator to have information about the levels of resistance of materials to hypothesize about the amount of heat released at different locations in structures. Though, as you said, testing tools designed to measure resistance levels of materials might be very expensive, a firefighter is one example of a person who might have access to a compiled database providing this type of information for investigative purposes.

 

Is this still all about your game board?

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Bill
Smart Kits build Smart People
http://www.blueroomelectronics.com/

 

Yes, I’m still working on the game board too. I thought that maybe geologists might also have information about the resistive properties of materials, or at least raw materials.

 

As pointed out earlier, even if you had such a material how would you determine more than one game piece's location? or for that matter how do you make an X-Y resistive sheet? Your game piece would have to connect across a grid to indicate it's position.

__________________
Bill
Smart Kits build Smart People
http://www.blueroomelectronics.com/

 

If I had such a material – assuming that you’re talking about a type of material that can measure distances as a function of electrical resistance, then I might be able to determine more than one piece’s location by first identifying three imaginary points on the material. I believe that it is then possible to identify the location of any point on the game board - occupied by one of these pieces, as a function of diameters of three imaginary circles defined as having a center coincident with these three points - by considering a point where the circumferences of the three imaginary circles intercept. I think that these three points might have to be carefully selected because I know that at least one of the points can’t intersect the center of an imaginary line segment connecting the other two points - if all locations on the game board are to be identified. These diameters might be able to be measured if a source of electricity is placed at the center of these three imaginary circles on a piece of material that can be used to measure these diameters as a function of resistance per unit distance. Turning off at least one of the other two sources of electricity that connect to the center of the imaginary circles might make the game piece’s location be identified more easily and accurately – by preventing the electrical signals of the game pieces from interfering with each other.

I don’t know how to synthesize an X-Y resistive sheet, so I am looking for one. I’d like to find such a sheet because a location identifying grid would detract from the game’s aesthetical appearance. However, I am still considering such a grid.

As for identifying different models of electrical resistance, I am identifying professionals who are involved in investigating electrical occurrences in materials. So far, I have only thought of fire investigators and geologists.