Voltage loss and its relationship to metal thickness?

[darren molnar]

Hello Gurus, I'm working out a design for a mechanical (wood) box mod, and I'm unsure about this relationship. I want to make something that performs as good as possible and, of course, real world designs come down to managing the compromises that inevitably show up.

As an example that relates to the question, imagine a brass flat bar that connects the negative of the battery at the bottom of the mod, to the neg. of the 510 connector at the top of the mod. Would there be less voltage drop if the bar was, say, 1/8" thick compared to one that was 1/32"? Assuming that the width and length are the same on both. If there is a difference, how great would it be? Is there a formula that engineers would use? Is there a point where extra thickness becomes irrelevant? I'm ultimately looking for minimal voltage loss running 1 ohm coils or a bit lower.

Any input would be greatly appreciated. You gentlemen and gentle ladies commonly astound me with your knowledge of such things here on this forum!

 

[Innocuous]

yeah, there are conductivity tables for metals - check google.

 

[retird]

Voltage drop across a component can be calculated by knowing Resistance & Current flowing through that component. V=I*R where I= current in Ampere & R= resistance in Ohm.

Brass is not as good of a conductor as silver, copper, or aluminum....

 

[Mitey F]

Voltage drop across a component can be calculated by knowing Resistance & Current flowing through that component. V=I*R where I= current in Ampere & R= resistance in Ohm.

Brass is not as good of a conductor as silver, copper, or aluminum....

This isn't terribly helpful, as he trying to calculate the resistance...

The short answer to your question is "yes". The more cross section you have in your piece of conductive material, the less resistance, and the less voltage drop. However, you will reach a point of diminishing returns fairly quickly with something moving as little electricity as a mech mod.

This should help, at least a bit.

Resistance

 

[retird]

You are entitled to your opinion as to helpfulness, my friend, but using the best conductor material, such as silver or copper will better resolve voltage drop as compared to brass....conductivity of materials is important....

And from the link you posted I quote....

A third variable that is known to affect the resistance to charge flow is the material that a wire is made of. Not all materials are created equal in terms of their conductive ability. Some materials are better conductors than others and offer less resistance to the flow of charge. Silver is one of the best conductors but is never used in wires of household circuits due to its cost. Copper and aluminum are among the least expensive materials with suitable conducting ability to permit their use in wires of household circuits. The conducting ability of a material is often indicated by its resistivity. The resistivity of a material is dependent upon the material's electronic structure and its temperature. For most (but not all) materials, resistivity increases with increasing temperature. The table below lists resistivity values for various materials at temperatures of 20 degrees Celsius.

 

[Mitey F]

You are entitled to your opinion as to helpfulness, my friend, but using the best conductor material, such as silver or copper will better resolve voltage drop as compared to brass....conductivity of materials is important....

And from the link you posted I quote....

A third variable that is known to affect the resistance to charge flow is the material that a wire is made of. Not all materials are created equal in terms of their conductive ability. Some materials are better conductors than others and offer less resistance to the flow of charge. Silver is one of the best conductors but is never used in wires of household circuits due to its cost. Copper and aluminum are among the least expensive materials with suitable conducting ability to permit their use in wires of household circuits. The conducting ability of a material is often indicated by its resistivity. The resistivity of a material is dependent upon the material's electronic structure and its temperature. For most (but not all) materials, resistivity increases with increasing temperature. The table below lists resistivity values for various materials at temperatures of 20 degrees Celsius.

I was not questioning your advice on material choice, only your referencing Ohm's Law. I thought it clear that the OP had considered Ohm's Law, and was asking a question regarding resistance based on cross sectional diameter of a material, not what material to use.

 

[retird]

I guess I missed where the OP referenced Ohm's Law.....I thought he asked " Is there a formula that engineers would use?"

Maybe my post was helpful to the OP and others with more information will also post.....hope ya get the info you are searching for....

 

[Mitey F]

I guess I missed where the OP referenced Ohm's Law.....I thought he asked " Is there a formula that engineers would use?" But, it really matters not as long as those who post here help him out....and he achieves his goal......voltage drop, for those wanting to do "sub-ohm coils", is a big deal....

I know, I haven't built anything other than sub-ohm coils in ages. However, this was his question

Would there be less voltage drop if the bar was, say, 1/8" thick compared to one that was 1/32"? Assuming that the width and length are the same on both. If there is a difference, how great would it be? Is there a formula that engineers would use? Is there a point where extra thickness becomes irrelevant?

The answer is "yes", not V=I*R

 

[retird]

Darren..... I did a quick calculation on the following:

20 guage awg copper wire (typically used in electronics wiring)(wire cross section in circular mills is 1020)
Voltage source = 3.0 volts DC
length of conductor = 1/2 foot
Load applied = 5 amps

VOLTAGE DROP = 0.052
VOLTAGE AT LOAD END OF CIRCUIT = 2.948 VOLTS (PER CENT VOLTAGE DROP= 1.73%)

SAME SPECS AS ABOVE FIGURED AT 6 VOLTS DC = Voltage at load end of circuit = 5.948 volts with 0.87% voltage drop

NOTE; INCREASING THE WIRE SIZE WILL REDUCE THE VOLTAGE DROP.....YOU CAN RUN YOUR OWN CALCULATIONS USING THE LINKED CALCULATOR....


The above calculation was done using a calculator ( http://www.genuinedealz.com/voltage-drop-calculator ) that allows for copper or aluminum and not brass....

here is a chart of ohm ratings by conductor material so you can compare the ohm ratings....

http://www.radio-electronics.com/info/formulae/resistance/resistivity-table.php

as you can see....the voltage drop in very minimal at a length of 6 inches using 20 awg copper wire...

hope all this jargon helps ya out ..

 

[darren molnar]

All these posts have been very helpful, I thank you all very much. After innocuous mentioned conductivity tables I started looking for them and found some great stuff. I'm sorry,I should've posted back earlier. And thanks for the link Mitey f, very helpful.

rtrd, I'm glad you mentioned that other metals would be more conductive. This is all still "on paper" and originally I did plan to use aluminum.

I'm thinking about brass right now only because of Galvanic corrosion. I've read that stainless steel (ultimately what the atomiser is made of) will react rather strongly with aluminum.I'm worried about it, but I'm not sure if it's as big a deal as I imagine it.
I ruled out silver because of cost and softness (maybe wrongly, I haven't priced it out), and copper because this is going to be a bottom feeder, and I don't want copper touching my juices.

but I'd appreciate your thoughts on this. Should I worry about aluminum and galvanic corrosion? I'm under the impression that it is one of the more reactive metals. I have this fear of building something that works great in the beginning, and then the performance drops off and I'm left with something that is too 'high maintenance' to use in the real world.

 

[darren molnar]

Just reading this right now, Thank you so much!

Darren..... I did a quick calculation on the following:

20 guage awg copper wire (typically used in electronics wiring)(wire cross section in circular mills is 1020)
Voltage source = 3.0 volts DC
length of conductor = 1/2 foot
Load applied = 5 amps

VOLTAGE DROP = 0.052
VOLTAGE AT LOAD END OF CIRCUIT = 2.948 VOLTS (PER CENT VOLTAGE DROP= 1.73%)

SAME SPECS AS ABOVE FIGURED AT 6 VOLTS DC = Voltage at load end of circuit = 5.948 volts with 0.87% voltage drop



The above calculation was done using a calculator that allows for copper or aluminum and not brass....

here is a chart of ohm ratings by conductor material so you can compare the ohm ratings....

Resistivity Table / Chart :: Radio-Electronics.com

 

[retird]

I did a quick google on brass and found this....

The composition of brass is normally made up of copper and zinc. More specifically it is usually 68.5% to 71.5% copper, .07% lead, .05% iron with the remaining ingredient being zinc.

My experience over 40+ years in the electrical field is that copper is better than aluminum....short answer is aluminum expands/contracts more and can oxidize.

I can't speak to the effects of juice touching different metals.....

 

[darren molnar]

Thanks again, your posts have me thinking about a bottom feeder design that would be completely isolated from the metals used in the mod itself. I think it might be doable, and would allow for more options in the choice of atomisers also.

I'm glad I started this thread, this is all very helpful.

 

[Visus]

Check this post its broken down to milli's and how much loss per 6inches

 

[Rader2146]

Resistivity, Conductivity and Temperature Coefficients for some Common Materials

The electrical resistance of a wire is greater for a longer wire and less for a wire of larger cross sectional area. The resistance depend on the material of which it is made and can be expressed as:

R = ρ L / A (1)

where

R = resistance (ohm, Ω)

ρ = resistivity coefficient (ohm m, Ω m)

L = length of wire (m)

A = cross sectional area of wire (m2)

Once you determine the dimensions of your conductor then you can calculate the resistance and voltage drop across the conductor. There will certainly be a point of diminishing returns, but that up to you to determine how much loss is acceptable. If you can get down to <0.2v loss at the atty with a 1.0Ω coil you will be in the running with the best mechs on the market.