LED Strips on a control panel

[Whislter65]

Hi guys

 

just a quick question.

 

Instead of using LED's with resistors with a momentary switch  on a control panel are you able to use LED strips instead?

 

I have tried searching through the site but everything comes up with Non DCC and lighting for coaches. I do realise that LED strips are for 12v usage but I'm sure someone can explain whether this can be done or not, and also what is required.

 

Just to add I am using Cobalt Digital point controllers

 

regards

[Ray H]

I'm not sure I follow the idea of using a momentary switch. By its very nature it would mean that the LEDs (or any other circuitry you use the switch for) are only powered briefly and if you blink you may well miss it/them.

 

Dare we ask what you're trying to achieve because, if your heading the way I think you are we may be both on the same bus, so to speak.

 

That said, I believe you can get strips of LEDs that can be used either in their ready made lengths or broken down into single (or perhaps double) LEDs.

[Whislter65]

Ray

 

What I am wanting to achieve is for the line which is in use to light up with a LED strip instead of using separate LED's. Use the momentary switch to change point direction then the other line would light up.

 

Dutch

 

If that is the case would I then wire them up exactly as the same as I would do for normal LED's. As I am using digital Cobalts the two positive sides of the LED go to the power bus and the two negative sides join together and go to the frog switch on the motor.

 

regards

[corax67]

If you are using the same stuff I use then I just cut lengths of strip to the appropriate size and solder to the tabs marked with plus & minus the wire in as any other LED or bulb.

 

Mine runs off anything from 3v to 15v DC, just the brightness that changes.

 

I like the idea of using it as route indication on a switch panel though, hadn't thought of that but then again I run DCC so everything is live all the time

[Whislter65]

If you are using the same stuff I use then I just cut lengths of strip to the appropriate size and solder to the tabs marked with plus & minus the wire in as any other LED or bulb.

 

Mine runs off anything from 3v to 15v DC, just the brightness that changes.

 

I like the idea of using it as route indication on a switch panel though, hadn't thought of that but then again I run DCC so everything is live all the time

Karl

 

I'm running DCC as well. So I'm assuming the monetary switch stays as it is without the need to change it. So would I need a resistor with these strips or are they built in?

[Phil S]

I am assuming you are planning to use the 12V LED strips as track occupation displays - whether triggered directly or indirectly by some unspecified track occupation detectors.

 

The '12V' strips I have been using (many types) with 1 exception, use 3 LEDs in series with a current-limiting resistor. This combination takes the expected current at 12.0V ie 20mA per set of 3 LEDs (or 50mmm of strip).   A useful test is to power a whole 5m reel, at 12V and measure the total current consumption. (300 leds = 100 sets if 20mA = 2A 0r 24W)

 

IF you use them with an 'unregulated' higher voltage, the current climbs rapidly ... as the resistor (linear) was selected for 12.0V, and the voltage across the LEDs will remain the same... only the current increases through them, and the resistor.  By 14-16V supply, the current has doubled, and therefore the heat dissipation has too.

This can be 'offset' if they are run off dcc, by half-wave rectifying ... as the extra power is only consumed for half the time. No flicker will be observed due to the high frequency.

Having all of them rectifying the same way, producing an unequal load between the 2 polarities of dcc (or sinusoidal ac) ...especially if you use assymetric braking, is best avoided anyway, is try to have half each way - perhaps even within a coach, if you are using them for coach lighting.

To avoid possible problems with low reverse breakdown voltages of LEDs I usually spend less than 1p extra by using a 1N4148 diode in series with such 1/2 wave usage.

 

YOUR apparent planned usage is for 'TRACK DIAGRAMS on a CONTROL PANEL showing OCCUPATION (?)

There are now some multi-colour strips - I don't jnow if these would be suitable for route indication - eg Set and Clear, Occupied / Locked ???

Equally there are multi-legged RGB LEDS if you are wiring your panel individually.

You may find the fixed-nature of the 50mm group of LEDs rather restricting - depending on the complexity of your track geometry.

 

I used the Hornby Micromimic system with my Zero-1 and have now, 'in dcc' replaced it with both 'glass panels' (computer screens) and re-used Hornby Micromimic Boxes and 'lighthouse'LEDs (but any compact pegboard might do) ,,, fed from dcc steady-state decoders (re using MERG decoders) ... however, this is for points and not occupation.

Only in a few specific storage locations do I plan to show 'occupation' on the same display .. leaving this to the computer grpahics as its easier to draw the lines in various colours.

[Ray H]

I think he is thinking the same way as me - to use the LEDs to show which route(s) is set as an aid to stop driving a loco towards an incorrectly set turnout.

 

It is the use of the momentary switch that is confusing me. I presume he intends to use this to drive SEEP or Peco style point motors which in turn will operate a ON - ON style switch that will illuminate the relevant LEDs. My only comment there would be that if that is the case what if anything is he using to switch the polarity of the frog of the point?

[Crosland]

The short answer is yes, you can use any LED strip instead of separate LED's. The 12V designation is nominal, not peak value. Commercial LED strips generally have a rectifier and current control built in.

 

The ones being discussed are more likely to have a single resistor to control the current through 3 series connected LEDs. The groups of 3 are the wired in parallel. The strips are marked where they can be cut into groups of 3 LEDs.

 

Andrew

[corax67]

Karl

 

I'm running DCC as well. So I'm assuming the monetary switch stays as it is without the need to change it. So would I need a resistor with these strips or are they built in?

I don't fit resistors to mine, they have all that built in per 3 LED section - I just wire up, plug in & go

[Whislter65]

I think he is thinking the same way as me - to use the LEDs to show which route(s) is set as an aid to stop driving a loco towards an incorrectly set turnout.

 

It is the use of the momentary switch that is confusing me. I presume he intends to use this to drive SEEP or Peco style point motors which in turn will operate a ON - ON style switch that will illuminate the relevant LEDs. My only comment there would be that if that is the case what if anything is he using to switch the polarity of the frog of the point?

Ray

 

That is exactly what I want to achieve. The motors I am using are Cobalt Digital. So if I was to use a normal LED on either side of the point they get wired, positive(red) and positive (black) to the power bus. The negative feeds on both LED's are soldered together, fitted with a resistor which then connects to the frog on the specific point. This wire is then inserted into the frog polarity switch on the cobalt digital. So when the frog polarity switches so do the LED's. The switch on the control panel which is a momentary one which has two wires connects to the Cobalt Digital as well.

 

So at the moment I can all my points can be switched either by the NCE Powercab or the switches on the control panel. All I want to do now is set up LED's to show which line is switched and show the route

[corax67]

The other option is to fit a couple of strips to one of you cobalts and give it a go - if you haven't bought any strip yet then drop me a PM & I can sort some out for you

[Ray H]

I was wondering whether it would be possible to connect a (green) LED via a diode and a 2K(?) dropper resistor between the (electrically switched by point operation) frog and the opposite running rail to get the same result.

 

There'd be no current flow when the point was incorrectly set so the "wrong" LED wouldn't illuminate. The downside I see is that it doing this for a number of points could sap the power available to the handset.

[Crosland]

I was wondering whether it would be possible to connect a (green) LED via a diode and a 2K(?) dropper resistor between the (electrically switched by point operation) frog and the opposite running rail to get the same result.

 

 

Yes, you can do that, a led only requires a few mA.

 

A more general solution is to use an opto-isolator.

 

Andrew

[Ray H]

Part of my thinking was that it might minimise the risk of short circuits caused by approaching the point from the tail with the road incorrectly set.

 

My colleague and I are both using NCE PowerCabs on his O gauge shunting plank and we have to reset both handsets if a loco shorts out. Using the LED across the track would prove the frog was correctly polarised.