Confused, 2 diodes "face to face" = working???

Dear Artarms,

Um, shouldn't those 2 LEDs be wired in anti-parallel? (LEDs in parallel, in opposing directions?).

As LEDs are diodes (only passes power in one "direction" or polarity), I'm unclear on how the above diagram could be working???

How many "legs" does the Circuitron LED have? (2 or 3, I can't find a diagram on the Circuitron site)

Happy Modelling,
Aiming to resolve confusion,
Prof Klyzlr

face to face

I am not strong on electronics but they are definitely in serial.  They might not be face to face per the drawing but then they are back to back.  There are two connectors on each LED, short and long.  The short leads are soldered together at the top of the signal and the long leads make up the ladder.- N scale.

Thanks for your interest - I can't explain it any further except to say that it works.  I would welcome a better explanation.

Thanks for your interest.

Art

Dear Artarms, I suspect

Dear Artarms,

I suspect that the short leg of each LED is actually soldered to the long leg of the other LED,

this would make them "anti-parallel",
(connected in parallel, but in opposing directions),

and the schematic would look like this...

EDIT: We now know that the above effectively represents ONE "Circuitron 9306" LED array (2 actual Light Emitting Diodes in one physical 2-wire package or "Blob"),

Art has 2 such devices connected in series. See below.

Happy Modelling,
Aim to Improve,
Prof Klyzlr

Art, this might help

Each bi colour Led has 2 diodes within,

cheers

Steve

Edit: the Prof beat me to it

Now you have dobbed yourself in Steve...

Now I think I get it...

Dear Steve, Artarms,

Steve, your diagram is more correct though, because you're showing the complete "2 LED elements per physical LED 'package'"

Looking from the physical "plastic blob with 2 wires sticking out" perspective, this would gel with what Artarms is seeing, the "both short legs _are_ connected together".

However, from an electrical Point-of-view, your diagram has it all set out...

Let's try this then, as an attempt to get it all sorted out...

Each Blue Circle is one physical Circuitron LED.
(A plastic blob with a pair of wire legs)

INSIDE each physical LED package is 2 actual Light Emitting Diode electrical elements.
Each element is either a Red or a Green LED on it's own.

Connecting the "Bi Color" physical LEDs in series, in opposing directions "face to face"
(IE with "both short legs soldered together),

gives the result shown...
(There may be only 2 "physical packages", but there are actually 4 Light Emitting Diodes in play...)

For laughs,
- start from either side of the switch, let's say the LH side
- assume your finger pointing at the diagram is the + Voltage,
- and work your way around the circuit, let's say clockwise, to the other side of the switch,

the only rule is you can only travel along the sections where the big triangle arrow is facing in the same direction as you are wanting to travel...

In this case, travelling Clockwise, the triangular arrows at the _top_ of each LED are "in the right direction",
and thus are the LEDs that will "light up" for that polarity of DC volts.

You can try the reverse, by starting at the RH side of the switch, and tracing the path travelling anti-clockwise... 

Artarms, please forgive the un-intentional hijack, I just had to get to the bottom of your "2 LEDs face to face" schematic...

Happy Modelling,
Aim to Improve,
Prof Klyzlr

I know you said you are using

I know you said you are using Tam Valley but here is a diagram for a Tortoise switch machine.

Sorry, but ... what means "a

Sorry, but ... what means "a Tam Valley relay on servo" ?

Anyway, here are some suggestion from Duncan web site:

http://www.tamvalleydepot.com/products/octopusservodriver.html

See at middle page the schematics. OR... just buy a $2,50 Fascia controller and unsolder the button?

...

I have a pile of LEDs where the short leg is not the negative lead.  It's better to go by what is printed on the led itself than the length of the wires.

Thank you all for your

Pile of LED's

I have a pile of LED's with nothing printed on them...

If it's possible to see the "guts" of the LED I look there to tell polarity.  The contact with the largest mass inside the LED is the cathode or negative contact, IIRC.

There is an easier way Kevin...

Apologies

Dear Art,

My apologies for any offence I may have caused. My comments, in chronological order or appearance,
were only "following the evidence" provided based on known basic electronic principles.

Totally agree and now understand the description of the build, factoring in the 2-wire Bi-color "LEDs" being used.
Unfortunately, Circuitron do not appear to provide any pics or schematics "pre-sale", and many bi-color "LEDs" are offered in 3-wire packages. This is what prompted my very first question "How many wires/legs do the LEDs in question have?".

Again, I apologise for any offence. The "diagnostic sequence", while technically correct, was obviously not on the right track until the very end...

Happy Modelling,
Prof Klyzlr

Larger "bit" = negative

Dear Kevin,

I have to admit I rarely if ever look at the leg/wire lengths, I focus on the guts of the LED itself as you've described.

Larger "internal" bit = flat molded into body = shorter "leg" = Negative terminal

(Single Color LED shown below)

Of course, bi-color 2-leg "LEDs" have one internal Light Emitting Diode element which obeys this rule, and the other connected the other way, which appears to defy the rule.
(Yes, technically there are 2x Light Emitting Diodes in one physical "LED" package). 

In _Professional_ applications, the spec-sheet for such LEDs will usually state which of the 2 colors available is the "Normal" (follows the established international diode polarity rules) one...

...and when it comes to SMD LEDs, best to flip the LED over and follow the "T" shape on the back for guidance...

Happy Modelling,
Aim to Improve,
Prof Klyzlr