The Taking of Pelham 123

What kind of track are you using? I'm hoping you'll say Atlas, Gargraves or Ross. Those brands have their outside rails insulated from each other, and make detection lights very simple.

Your right, I should have listed this.  I'm using all Atlas O Nickel Silver track and their switches.

Paul

Corvette:

Check out this site for a control similar to what you're after:

http://launchpad4mrr.blogspot.com/

I haven't followed all of the links it contains, but things like the helix indicator looks pretty interesting.

Neil

GTW.

I went to that site and if I read and understand that setup correctly, the lights or mounted on the infrared sensors.  I want a board on the wall showing the progress of a train moving around the track.

Corvettte

Paul, you don't need to go to all the trouble in Neil's link. That article is a method that 2 railers might need to use. God has blessed us with a third rail, let's use it!!!

You have perfect track for this, because the two outside rails are electrically isolated. You'll need to designate one outside rail as the ground rail for running, the other outside rail will be for detection. You'll have gaps in the detection rail. For subway every 3 feet would be cool. But remember, every segment you make will need a wire back to the panel, and an LED. The finer you dice this, the more labor and expense it run you.

It is very simple to do a single color LED in an on-off configuration, red-green is more complicated. You will need a proper DC power supply for the LED's. That's not my thing, but I'm sure someone here will be able to help, if you need it. The ground side of the supply can tie right to the track ground of your layout. The other side of the supply will go to the correct leg of the LED's. The other leg of the LED is connected to the wire coming from the detection segments of the track.

Train axles bridge the outside rails and complete the circuit, LED on.

BTW, I didn't like the new one with Denzel Washington. The original was much better.

If you only use 1" of track to detect occupancy and directly drive the LED circuit(s), I'd think the LEDs would flicker as the space between axles would surely exceed 1".  If the train stopped with axles on either side of the 1" track section, it seems you'd have a dark LED surrounded by lit LEDs assuming your train is longer than 20" or whatever you set your sensor spacing.  That might look funny.

But all of these can be solved by inexpensive logic or timer circuits...less than $1 per circuit.  The biggest problem as you've identified is to step-up and wire all those occupancy detectors.

If cost is not an issue, it might be fun to concoct some scheme where you only run a few wires or a "bus" along the track.  Each sensor would have a unique address X and would send a message to the master saying "activity detected on sensor X".  The master would decode these messages and refresh the display board accordingly.  This would drastically simplify wiring but requires more "sophisticated" electronics.

But no matter what you do, it would be very cool indeed.

Hi  Stan,

Please expand on your idea of logic or timer circuits.  What are they and how would they be wired into the system ?

Corvettte

Do you really want to get involved in a big electronic project when you don't have to?

The entire mainline on my layout , well over 1000' when complete, will use the detection method I outlined in my earlier post. However, I won't be driving LED's on a panel. I have a system called CMRI, which stands for Computer Model Railroad Interface, that I purchased over 20 years ago. Each detector wire will tie to an input bit in the system. Once the computer knows where the trains are, it can activate output bits, which will throw switches and change signals. With that information, I can have a virtual control panel, and put it up on a big screen.

What you are trying to accomplish is quite basic, and doesn't require timers or special sensors, and certainly not a computer. It takes a plan, time and wire.

I can't find an email address for Stan2004.

Could someone explain to me what he meant by using "logic or timer circuits" do, and how do they wire up to this setup ?

Corvettte

I think Elliot's solution solves the problem and you can forget all the extra timers and the like.  You can have resolution down to as small as one track section if you don't mind running lots of wires!   There are fancy electronic solutions to minimize the wiring, but I'd look to see if Elliot's solution does the trick for you.

Hi Elliot,

I went to  Launchpad4mrr.  I read about the helix.  That led me to the website  Good Luck Buy which is the place that sells the sensors.

I'm a bit lost as to just how this system works, so I will call them Monday and get someone to explain to me just how what they sell would work for what I want.

It sounds like this may be just the thing for what I want to do.  That's if I decide to do it.  I may be over my head on this one.  But I'd like to try on a small scale to start with.

Stan, I know you tried to explain to me about the CMRI system.  You went over my head.  When I stop swimming in all the new information I'm trying to digest, I'd like to contact you to see if you can further explain your idea to me, but I see your profile does not have an email address.  Maybe you could email me.    corvettte@charter.net

Corvettte (Paul)

Thanks John.

Stan, I'm not advocating the use of CMRI for Paul's application, quite the contrary. Unless he wants to do something more than simple detection with a lighted schematic panel, similar to what was in the movie, there is no real reason to get into any fancy electronic solutions.

Paul, if you plan to actually do this, regardless of the method, you'll need to start with a couple of basic things which are common to any solution.

First, identify and isolate one outside rail over the entire layout where you want detection.

Second, cut that rail into segments, using gaps or insulated joiners, whatever is easiest. The segments should be minimum one car length, no real maximum, but I'd recommend between 24" and 36".

Third, run a wire from each of those segments back to where you want your panel.

Complete those three steps and the hard part is over.

Elliot is right, once that part is done, wiring up position sensing lights on a board will be very easy.  As far as flickering LED's, some small filter caps will fix that.

In the simplest form, you can simply wire an LED, current limiting resistor, and a capacitor from a 12 VDC power supply and have the track sense wire complete the circuit.  Simple and effective.

Elliot is right. If you can increase your sensing track sections to a car's length (rather than 1") things become much easier since you will always have several axles on each sensor at any given time.  Then you can use basic electronics as Elliot and John described.

I over-complicated your application by turning into different problem where you try to reconstruct or recover data from incomplete information which is what you have if you use a sensor distance shorter than the axle spacing.  In such situations you would need more complicated logic whether implemented in hardware such as what I was suggesting and/or in software with the CMRI system being one option.

John, Elliot is right. 

Boy, this is what I need you guys for.  What you have in your brains that I don't.

Now I understand why I need a section way longer than 1".  It needs to be long enough so that at any given time, at least two cars should be on that section so that should eliminate any blinking of the light on the panel.  Is this on track ?

John, please explain what a filter cap is, and what a current limiting resistor, and capacitor does and how to wire it.  Sorry, I'm a little lost on that part of it, but if this is what it takes to make this idea work, I'll follow your advise.

Paul (Corvettte)

Assume 12 volts DC to power the panel. The negative side of the 12V supply goes to your track common, i.e. the powered outside rail.  The positive side of the 12V supply is used in the panel as detailed below.

Assume you have the sense track divided up into the desired sizes and have a home-run wire from each section.  Note that the sections could be simply a single track length if you want more resolution, that will be more than enough to insure you have a set of wheels on the rail which should be all that you need.

For each track section sense wire, wire it to the negative side of the capacitor and the LED.

From the 12VDC power supply positive terminal, put a 100 ohm resistor and a 1000 ohm in series with it coming into the panel.  Wire a 100uf 25V electrolytic capacitor from the track sense lead to the junction of the resistors.   Wire the LED with the positive terminal to the end of the 1000 ohm resistor.

This provides a small resistance to avoid sparks charging the filter capacitor, current limiting for the LED, and filtering to avoid flickering of the LED.  I've attached a schematic of the connection below.

Don't worry Paul, we're here to help. We'll talk you through the whole thing. A big part of what makes all this fairly simple is the fact that you are using Atlas track. Had you said Lionel or MTH, the discussion would have ended there because it would have been too difficult to do the detection segments, because those brands of track have their outside rails bridged.

How big is the layout? I'm asking to try and get an idea of what size wire you'll need. I'm thinking a Cat 5 cable might be just the ticket.

What is the track plan like? Curious to hear how big this project will be.

Elliot, I don't think wire "size" has much to do with it, almost any wire will light an LED.   I like the idea of CAT5 as you can run one wire back to handle eight track segments.

I'll bet this would look pretty cool, it's an interesting idea.

I was just thinking about voltage drop, but it probably won't come into play. Perhaps simple 4 conductor phone wire would be better than Cat5. Depending on the length of each detector segment, fanning out the 8 wires could mean that he would need to un-jacket as much as 12' of the cable to reach the far segments of the group. The use of simple phone wire will result in twice as many cables, but less waste and less length of single wires trackside.

If he goes through with this, I want pictures when he's done!

I figured that the current will be in the 10ma range.  For 100 feet of #24 wire, here's the results.

Voltage drop: 0.051
Voltage drop percentage: 0.43%
Voltage at the end: 11.949

Probably not a problem.

I didn't think unwrapping the wire would be a problem, but whichever way works best for the job at hand would do.  I certainly wouldn't be worrying about the voltage drop, given we're just powering an LED.

Size of the layout is as follows:

One table is 25' x 10'. 

There is a space between that table and another table of 4' going the length of the 25'.

The other table is 8' x 25'3".

Above that table is a second tier which is 8' x 20'.  This second tier will be dedicated solely to a 40s hump freight yard with a smattering of when the diesels first came in to service.

I have a total of 612' of table.

Wires running from the furthest part of the layout to where I would like to place the track diagram panel will be approximately 39'.

I have pictures I have taken during each step of the construction of the layout tables, but I didn't want to bore everyone, but if you would like to see what a novice has done, let me know and I'll post them.

Corvettte (Paul)

Somebody explain to me how to post pictures.  I just realized I have never done that.

Paul

Rich has that covered, here's the thread: Posting Pictures From Your Computer

The distances you speak of aren't a problem with any wire you'd like to use.  Smaller gauge is cheaper.

John, I read over your schematic, and to my surprise, I understand it.  If I'm following what you said, this procedure is primarily to stop blinking of the light on the board ?

Paul

Thanks John,  I never noticed all that stuff down in the left hand corner.

Paul

The extra 100 ohm resistor and the cap is the "filtering" to avoid blinking on the board.  You could use just the 1000 ohm resistor and LED if you don't mind some flickering of the display.  I tend to like "perfection" in my displays.

I like your idea John, so when the time comes to test out my idea, and wire up 2 or 3 sections of track, I'm going to contact you to make sure I wire up the system just as you say it should be.

You guys have got me really raring to go with this thing.  I've got a ways to go until I get to that part, but I WILL try it with your help.

Thanks, Paul

It really is as simple as stated.  As long as you have the isolated track sections, you just wire indicators to them.  You can just try one or two and see it work, then get out the big roll of wire and have at it!

Well all I can say is "Thanks To One And All".

I will let you know what happens when I try this out.  In fact I'm so hyped up to try it, I may just for the heck of it, after I get 25' of track laid, I will try, say, 3 sections wired to 3 LED lights just to test it to see how it works.

Thanks again,  Paul (Corvettte)

John,  now don't laugh at me if I get the following wrong.

What little I know about resistors and capacitors is as follows.

Your diagram shows 2 resistors that I assume reduce the current going in the LED.

The capacitor I think stores current so the light will stay on for a determined amount of time so it won't flicker.  And as each new axle passes over the section of track it will send another shot of current to the light.

Do I have that right ?

Corvettte (Paul)

HA HA HA!   I had to get that out of my system.

You have it correct.  Actually, to reduce the current, only one is really needed.  However, since the initial surge of current to charge the capacitor may cause arcing, I put the smaller resistor in front of it to minimize the current surge.  The capacitor placed before the larger capacitor so it gets a higher voltage charge, thus more energy, and it'll keep the LED lit a bit longer between any voltage drops. 

The circuit assumes continuous connection by the wheels, but allows for a very brief interruption of the circuit before the light goes out, just enough to prevent flickering.  Just as you'll notice many passenger car's lights flickering as they run down the rails, the same would happen to this circuit with no filter, even though the cars are continuously powered.  When I put LED conversions in my passenger cars, I also have a filter cap to eliminate the flicker.

Thanks John,

I've learned quite a lot just in this post.

I will be trying this out even before I build a wall panel just because I want to see this system work.

Thanks for everything.

Paul

Always a good move to do a test before you commit to a large scale project, can't argue with that.