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Author Topic: Isolating LED on control board  (Read 156 times)

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Offline IanF

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Isolating LED on control board
« on: February 16, 2020, 10:01:05 AM »
Hi - before embarking on my larger layout I thought I better get a grip with DC wiring. So I built a small test track with 2 points operated by SEEP PM1 motors and 5 isolating sections. Built a control board with green & red LED lights connected to the on-off switch for the isolating sections (and on-(off)-on for points).
Problem is the LED is a diode so when I use my Gaugemaster Combi to reverse the polarity then the lights won't work. How do I get around this? I'm guessing a separate 12V supply but how would I wire that without getting the full 12V onto the track when I switch an isolated section on? ???

My version of a wiring diagram attached - as you can see I am no electrician.

Help - I don't know what I'm doing

Offline PLD

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Re: Isolating LED on control board
« Reply #1 on: February 16, 2020, 10:43:25 AM »
I'm not clear what you are wanting the LEDs to indicate...

Is is a "Power On" indication (illuminated whenever the track is live) - in which case you need to use double pole switches and a separate power supply for the LEDs.
Is it a "Train in Section Indicator" - This is the only case where it might be appropriate to have the LEDs powered by the track supply
Is it a "Point Position Indicator" - Again a separate power supply is needed and would want to be controlled by a switch on the point motor.

Online Bealman

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Re: Isolating LED on control board
« Reply #2 on: February 16, 2020, 11:03:43 AM »
I've always kept any signalling circuitry,  be it panel indicators, or actual signals on the layout, separate from loco control. Apart from point swiches, that is the only interface.

My system can detect locos on track, but that's done by an elaborate system of optocouplers and relays.

And yes, it is DC.

Vision over visibility. Bono, U2.

Offline ntpntpntp

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Re: Isolating LED on control board
« Reply #3 on: February 16, 2020, 11:12:02 AM »
As @PLD   says, for control panel LEDs to indicate an isolated section is on you need to use a separate power supply and another separate pole on the switch, ie. you need a DPST switch.   To be honest I find the physical position of the toggle switch is enough to indicate that the section is switched off or on, and the LED is just unnecessary additional complication.

You mention ON-(OFF)-ON switches for the points - they're the wrong type: you need momentary contacts, ie. (ON)-OFF-(ON)  toggles - or push buttons, or stud-and-probe operation.   The problem is a DPDT of that sort of toggle switch won't provide a constant contact to light an LED indicator for the point.  The traditional approach, although it involves rather more wiring, is to wire an auxiliary changeover switch from the point motor back to the control panel. The problem with that is if you've already used the built-in changeover of the Seep motor for point frog power then you need to work out how to fit an additional switch.   An alternative is to use one of the electronic modules available which "remember" point switch operations and can light indicator LEDs for you.  I'm not a fan of those as they're not actually physically connected to the point tiebar. 

As with section switches, I don't bother with LEDs now for points (I used to back in the 80s), I just train anyone operating my layout to trace their finger along the desired route on the control panel and press all point buttons/toggles along the route.


This my most recent control panel, with just switches for sections and points (half a dozen signals came later). I've since added coloured sleeves to the toggles to further distinguish sections from points from signals.


« Last Edit: February 16, 2020, 11:22:26 AM by ntpntpntp »
Nick.   2016 celebrating the 20th anniversary of "Königshafen" exhibition layout!

Online Bealman

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Re: Isolating LED on control board
« Reply #4 on: February 16, 2020, 11:28:24 AM »
Yes, I agree when it comes to isolating sections, lights are total overkill.

Toggle up is isolated, toggle down is live.

The switch is only bridging a rail gap..
Vision over visibility. Bono, U2.

Offline IanF

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Re: Isolating LED on control board
« Reply #5 on: February 16, 2020, 11:55:21 AM »
Hi all,

Thanks for the replies - great help. Obviously a stretch too far with the lights. I did describe my point switches incorrectly - they are momentary contacts and I'm using a CDU unit.
With the isolating sections I was trying to show which was 'live' and which were off. I might try the separate supply with the DPST now that the lights are in there.

So I could simplify it for myself on the larger layout (when I get around to it). I still like the idea of lighting for the points direction so I'll see what I can do there. For the time being though I'm glad I went through this process BEFORE the big build - I have learned a lot.
Thanks
Help - I don't know what I'm doing

Offline chrism

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Re: Isolating LED on control board
« Reply #6 on: February 16, 2020, 12:28:29 PM »
So I could simplify it for myself on the larger layout (when I get around to it). I still like the idea of lighting for the points direction so I'll see what I can do there.

I use little latching relays for that - with the impulse for changing the relay setting being the same one as comes from the momentary switch (or, in my case) stud & probe to fire the point motor, tapped off the two wires to the point motor. With the relay set one way it lights one LED, the other way it lights the other LED. The LEDs themselves are, as discussed above, powered off an independent 12v supply through suitable resistors of course. It has both an advantage and a disadvantage - the former being that, upon power-up, the indicators are already showing correctly unless someone's fiddled with a point manually and the latter being that the indicators will change even, for some reason, if a point doesn't.

It could be done using the switch built into the point motor instead but that means running more wires all the way back to the control panel and would also prevent you using the switch for switching the frog power instead of relying on the point blades contact should you wish to do that either now or in the future. It would, however, negate the disadvantage I mentioned above because the switch is physically tied to the movement of the point motor and point.



 

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