Reverse Polarity Switching

[paul1066]

Hi all, I’ve got these wonderful little ground signals to play around with but I’m a bit stuck how to switch them between the red / white and white / white aspects. Each signal has two wires so to change aspects you need to reverse the polarity, ideally I’d like to link the aspect to the throwing of the points and I’ve got two options for points detection - I can use the built in switch on my solonoid points or add a micro switch to the points bar but I’m at a loss how to reverse the polarity of the signal feed - any suggestions? Thanks

Paul
—
“Time flies like an arrow. Fruit flies like bananas”

[Brian]

Hi
The first question that needs answering is... Do you really need to change polarity i.e. positive becomes negative etc?
Or is it a matter of switching each LED? The pivot LED (lower right) will always be lit White (or Red depending on period modelled of the shunt signal).
Reversing DC polarity is done using a Double Pole Double Throw (DPDT) switch and is wired as per the drawing below...




What make are they?? If they are the DCC Concepts version I believe they are made to work with their Alpha mimic control boards.
If they can be switched as per the drawing above then don't forget a series resistor is needed in one lead to limit current to the LEDs
Please Note.... If they are the DCC Concepts Position Light Ground Signals (PLGS) and any incorrect wiring causes an LED to blow it is NOT covered by their warranty!

[paul1066]

Hi Brian, yes they are DCC Concepts ground signals and work by reverse polarity (I asked them) the lower right LED is actually two white SMD LEDs and so when you change polarity you either light a red and white or a white and white - four LEDs in total. I'm using them independent of the control board hence my question about a polarity changing switch. Thanks Paul

[Brian]

Dont forget you MUST add a series resistor into the Black lead. Its Ohm value will depend on what voltage the supply is at. Likely to be somewhere between 2K and 5K possibly?

[paul1066]

DCC Concepts recommended a 10k or 7k resistor for 12v but I have a 5v signalling bus on my layout so I will use something suitable.

[Tricky Dicky]

If you have SEEP PM 1 then you will not be able to reverse the current as the built in switch is merely a changeover switch. If you are using the PECO motors, I think you can rig up polarity switching using 2 PL-32 microswitches mounted on a PL-15 mounting plate, as far as I can remember the movement of the solenoid core activates both switches simultaneously but it looks an expensive proposal.

You might be better off using a DPDT relay to do the polarity reversing then you can use the SEEP PM1 switch or the cheaper PL-13 with the PECO motors or a microswitch activated by the tie bar.

Richard

[paul1066]

Aye, thanks Richard, I assumed the Seep wouldn't be up to it on it's own so will look at the other options. Early days yet.

Mind you, this does lead me onto what might be termed a fundamental question re signalling - with colour lighting, the nice pretty colours are only viewable along the "line of sight", so is there any point bothering if the only creatures who can see the signal lighting are the odd spider creeping along the back walls? To this end I've probably broken most rules and placed most of my signals where I can see them... oh dear...

Paul

[IanS]

Don't forget that the camera on the train during a run can also see them!

[Tricky Dicky]

Aye, thanks Richard, I assumed the Seep wouldn't be up to it on it's own so will look at the other options. Early days yet.

Mind you, this does lead me onto what might be termed a fundamental question re signalling - with colour lighting, the nice pretty colours are only viewable along the "line of sight", so is there any point bothering if the only creatures who can see the signal lighting are the odd spider creeping along the back walls? To this end I've probably broken most rules and placed most of my signals where I can see them... oh dear...

Paul

LEDs are somewhat directional as to how they emit light but even at acute angles you can tell if a LED is lit, but I do take your point. It is similar to the argument over fine detailing, can you really count all the rivets on a loco as it whizzes past you or even one standing in a siding when viewed from a normal distance? I must admit that I subscribe to the mode of modelling that something may not pass close inspection but if it looks right from a distance it is right enough! Now I am not knocking the fine modellers and will be the first to appreciate the skill and dedication that goes into fine modelling but it is not for me. At the end of the day its your layout, do what suits you

Richard

[Walkingthedog]

There are no rules Paul except yours. Your layout your rules.

Richard I’m with you, If I think it looks OK then it is.