Help selecting proper minimum wire gauge for LED install

Current divides into your 3 sections.   The Hennings module can be adjusted to put out up to 45 mA max (total).  So that's a max of 15 mA per section.  A pair of AWG 30 wire between each section is fine.

It divides?  whoo
I think my brain may explode, I am so not understanding that I am worried my explanation and picture is not clear.

give me a second and I will whip up a quick pptcad to be sure

Let's say the Hennings module is set to 45 mA (probably too bright but whatever). 

The pair of wires going from the Hennings module to the first section carries 45 mA.  The first section sucks off 15 mA of that current.  The pair of wires going between first and second section carries 30 mA.  The second section sucks off 15 mA of current.  The pair of wires going between second and third section takes all the "remaining" current of 15 mA and we're done!

so here is a crumby ppt schematic

I think all of the current needed for all the LED's has to flow thru the wires at 1, for a total of 9*.02=.18 amps

Then only 6 LEDs worth at 2 6*.02=.12amps

Finally 3 LEDs worth at 3 3*.02=.06 amps

To be VERY clear, I am not questioning your skill in any way.  I am perplexed and hoping this will turn into a teaching opportunity that will sink in on this side (me)

OK, I guess I am confused about the LED's themselves.

I think that they are current devices, and that they are 20 mA each.  This is where my 0.02 A is coming from.  Is this not true?

Also how do you know the PS is 45mA?  I tried to look it up but failed.

As always, I mean no disrespect, I am trying very hard to understand.

LED's, while being current mode devices, operate on varying currents.  I find that running the 12V strips at the full brightness looks silly in a passenger car, they're WAY too bright.  The reason the lighting module runs at 45ma max is that's more than sufficient to light a 21" passenger car.   I'm typically lighting my cars on around 20-25ma total from the supply.

The 45ma comes because of how the power module is built.  Since I built it, I can assure you that Stan's figure is correct.   The lighting module is a constant current supply, it supplies from about 5ma to around 45ma from mininum to maximum adjustment.

Here's an 18" car that is using 25ma (measured) with a full length LED strip.  This is about the level that I like my lighting to be.

You're right- I looked at the Hennings site and it doesn't seem to show this range for the PS.  The actual numbers don't matter for the purposes of this discussion wrt how current flows/divides/splits in these LED strips...so let's just use 45 mA.

First is to understand how the LED strips are configured.  The 3 LEDs within a section are "stacked" so that all 3 receive the same current.  If 15 mA is flowing thru one, then 15 mA flows thru the other two as well.

Additionally, each sections has a printed wire on the strip to join to the next section as shown in red and black in the diagram.  In your case you cut it into 3 sections using the blue wires as shown above.

As you say, LEDs are "current" devices in that brightness is exactly proportional to mA.  20 mA is a commonly used current for driving an LED, but 10 mA works just fine and emits exactly 1/2 the "photons" as an LED driven by 20 mA.   2 mA (or 1/10th) also works fine and will still be quite visible.

There are all kinds of analogies for current flow and how it splits/divides/joins or whatever.  For example, think of water flowing in a pipe at 45 gallons/minute.  Now you split the pipe into 3 separate but equal pipes and then join the 3 back to a single pipe.  I think it's plausible to believe that 15 gallons/minute will flow thru the 3 different pipes and will become 45 gallons/minute on the other side when joined back to a single pipe.

That's what's going on here.  As the word "circuit" itself suggests the current must go and come back.  What goes out, must come back....otherwise it wouldn't be a "circuit" (duh!).  So 45 mA goes out and splits as shown with the currents as shown and all 45 mA returns.  Each section gets 15 mA and each LED within each section gets 15 mA.

So in this example, the wire between the PS and the first section actually carries the total 45 mA.  The connecting wires between sections 1 and 2 carry only 30 mA.  The wires between sections 2 and 3 carry only 15 mA.  And of course there are no additional sections so 0 mA flows out the end of section 3.

You definitely do NOT need to double up the wiring as you move left to right.  If anything, you'd need to bulk up the wiring on the left which has the max current...though in this case with only 45 mA tops for the Hennings module you can safely use AWG 30.

If you buy the lighting regulator, you get an instruction sheet.  It says...

The LEDCCLR can supply constant current to one or more LEDs from 5ma to 45ma, the current is adjustable by a small adjustment potentiometer on the board.

Just have to read the manual.

Great explanation, Stan. I think BW was counting each individual led at 20ma, when it is closer to each three at that current.

Actually, if one of the group of three were seeing 20ma, you can be 100% sure that all of them are seeing the exact same current.   The current in other groups may be slightly different due to the characteristics of the individual LED and tolerance of the resistors.

It is a combination of multiple things.  I will try to explain what I was thinking.

GRJ
It is worst than you think, I bought both lighting kits and just supplies.  So I have the directions and did indeed READ them.  Just some how did not pick it up.  If I had I would have realized the the baddest it could be is 0.045A so 30 AWG would be fine, per my chart.

I was confused about LED's being current devices.  I was thinking that when they are lit, they use 20 mA. If they vary in intensity, voltage is changing, with same current.  I had not made the connection that reducing the current changes the brightness, so the 20mA is a super max.

John H
You are exactly right, I did not realize how it was actually wired, so I was doing exactly that.  I was thinking they are all in series, each LED using up a little current.  I guess this works out to each group of three is parallel with the groups in series?

Stan2004
I was indeed using a water analogy (which I am comfortable with becasue I am a ME)  becasue I did not understand how the strip was actually connected, or the bit about it not actually having to be 20 mA, your answer initially blew my mind.  The reason being I figured I just had it all completely wrong and that my water analogy was not working.  Instead, I think I had a pretty good grasp of the basics of the problem, I just did not understand the specifics of my situation.

All
thank you VERY much for being patient.  At some point I will get this.

How many times does one have to look at something before seeing it?

Well, I designed and wrote it, so I suspect that I have it more engraved in my brain than some.   All's well that ends well, I think we're on the right road now.