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Author Topic: LED's for mimic panel  (Read 297 times)

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Offline ColinR

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LED's for mimic panel
« on: October 24, 2018, 01:31:56 PM »
I've have a working double track layout with 3 passing loops on each track. It's DC and points controlled by stud/probe on a control panel. I wish to add some LED's to the panel to indicate whether a loop is live or not. A grain of wheat bulb across the track works but it's brightness is dictated by the speed control on the H&M controller and also whether there is a loco on that section.
Any thoughts appreciated.

Offline ntpntpntp

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Re: LED's for mimic panel
« Reply #1 on: October 24, 2018, 02:28:43 PM »
[edit] Oh hang on, you're not talking about track occupation, just whether the track power is live? I'll leave this comment on anyway! [/edit]
You need some form of track occupation detector that's independent of the traction power.   Some work by detecting a slight current flow on a separate circuit through the track  (conduction either through the loco motor or stock lighting, even a resistor across two metal wheels).  Others work using a magnet and reed switch, or an infra-red detector.

I've had a lot of success with infra-red detector modules by Heathcote Electronics, and use them to control automated shuttles, level crossing barriers etc.

https://www.heathcote-electronics.co.uk/
« Last Edit: October 24, 2018, 02:30:27 PM by ntpntpntp »
Nick.   2016 celebrating the 20th anniversary of "Königshafen" exhibition layout!

Offline ntpntpntp

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Re: LED's for mimic panel
« Reply #2 on: October 24, 2018, 02:35:40 PM »
Are you wanting to indicate that the track circuit is live even when DC power is off?   Is this a track section that's switched by a point motor or something (ie. not just by a section switch on your panel?)

The simple way when you have section switches is to use a DPST switch and use the other pole to switch an LED on or off.

If you want to feed back from a remote point motor then use an auxiliary switch on the point motor, wired back to the panel.   I did that with my fiddle yard, though the panels are mounted next to the yard so there isn't a long run of wiring to cope with.   


There are electronic modules out there which "remember" the last points thrown and can light an LED that way - but of course they rely on keeping in sync with point buttons or probe contacts etc.  Not sure I'd trust them!
« Last Edit: October 24, 2018, 02:38:03 PM by ntpntpntp »
Nick.   2016 celebrating the 20th anniversary of "Königshafen" exhibition layout!

Offline ColinR

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Re: LED's for mimic panel
« Reply #3 on: October 24, 2018, 03:33:01 PM »
The power to the loops is dictated by the points at entry and exit. If the points are switched to the main line then the loop is "dead" and vice versa.
Would LED's wired across the tracks work?

Offline dannyboy

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Re: LED's for mimic panel
« Reply #4 on: October 24, 2018, 03:37:08 PM »
I have not looked to see if there is anything suitable, but you could have a look at the Brimal Components website and see if there is anything of use.

www.brimal.co.uk
David.
I used to be indecisive - now I'm not - I don't think.
If a friend seems distant, catch up with him.

Offline class37025

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Re: LED's for mimic panel
« Reply #5 on: October 24, 2018, 03:42:54 PM »
on, IIRC, version 3 I used these

https://www.hattons.co.uk/7541/Peco_Products_PL_13_Accessory_Switch_for_fitting_to_turnout_motor_PL10/StockDetail.aspx

fitted to the point motors, then used them to power, dependent on point setting, LEDs on the track plan to show the route set.

the advantage being it doesn't need to remember previous settings, when you power up the layout, it's there.

KISS always works for me. :D
typed by fur box mechanic - dictated by brain on a chain

Offline Nigel Cliffe

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Re: LED's for mimic panel
« Reply #6 on: October 24, 2018, 05:38:44 PM »
The problem with switches under turnout motors driving LEDs on a panel is the amount of wire to run back from switches to the panel. It rapidly descends into spaghetti mess unless some serious thought to wire management is undertaken. 

Alternative, assuming what's wanted is direction indication (ie. a reminder of which stud has been operated):  use a device inside the panel to record which stud was used.  There are several options here, but a latching relay may be the simplest option. 
Brimal components list one mounted on a PCB with screw terminals for a fairly reasonable price (£5.51), though note that it is not suitable for being fired via a CDU.  So, if using a CDU, that needs to be arranged to not fire via the relay contacts.    Once you have the relay contacts, the LED(s) can be switched using a 12v DC power supply, LED and series resistor for the LED.   



Offline MalcolmInN

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Re: LED's for mimic panel
« Reply #7 on: October 24, 2018, 11:57:10 PM »
but a latching relay may be the simplest option. 
Brimal components list one
Might this be a job for a 555chip (20 for a £) configured as a bistable latch ?

Offline Nigel Cliffe

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Re: LED's for mimic panel
« Reply #8 on: October 25, 2018, 11:53:57 AM »
but a latching relay may be the simplest option. 
Brimal components list one
Might this be a job for a 555chip (20 for a £) configured as a bistable latch ?

Yes if one is able to put the relevant parts around it to provide power and deal with the volts from the stud contacts.   No if one hasn't much of a clue about electronics, hence suggesting an off-the-shelf assembled circuit.   

 

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