Installing Auto Signals: PM42 and Sound

[RexHea]

I have been installing the signal wiring that I have threatened to do for a year and a half . I now have the power districts wired and working, and will start breaking them down into detection sections probably after Christmas.

I was wisely talked into installing a PM42 for the districts, but one thing that I ran across that everyone failed to mention is they do not like the in-rush of current that QSI decoders have. The PM42 will operate just fine with only a few sound decoders in a district, but if you have a section with several then the 42 detects a short from the initial charging of the capacitors and can’t reset itself. Of course, if the capacitors are charged from another district there is no problem...until you short out the rails again.

Setting the OPSW’s in the PM42 helps, but that’s like putting in a larger fuse when you blow the correctly sized one (YIKES!). A way around this is to install auto taillight bulbs (#1156) across the command station inputs of the 42 to the individual outputs, i.e. Rail A to Rail A District #1 and (2,3,4), and Rail B to Rail B District #1 and (2,3,4), total 8 bulbs. Because of the"Positive Temperature Coefficient", they act as a shunt to this high surge current and allows the capacitors to charge without tripping the 42. After the charge, the PM42 breakers act correctly and the power districts are protected.

I realize that some of you all ready know about this and I do not claim to have originated the idea, but hopefully this will help others that are not aware of this potential problem.

 

[jbaakko]

Rex, I wonder if picking up a capacitor (or 4) to drop in, in place of the bulbs, might alleviate the problem? I.E. Adding a capacitor to the PM42's circuit.

That worries me a tad, with the sound decoder shutting it down, seems excessive to install all those bulbs.

 

[RexHea]

Tony's sells a unit (PSX4) that does the same job as a PM42, but is designed to handle the surge without a false breaker trip. However, it cost $158.00. The problem is the 42 was designed before sound came about and doesn't have a way to handle this where the PSX is full electronic and can sense/learn the surge and compensate at start ups.

I don't think a capacitor would do any good, but I'm not exactly sure how you are suggesting the use. The way an incandescent bulb works is with a positive temp coefficient it acts as a near short around the PM42 at initial startup and allows the capacitors to charge. As the filament heats the resistance goes up and the current then follows the path of least resistance through the PM42. This, of course, is in milliseconds. Bulbs were commonly used in the early days for short detection and so on.

 

[jbaakko]

Tony's sells a unit (PSX4) that does the same job as a PM42, but is designed to handle the surge without a false breaker trip. However, it cost $158.00. The problem is the 42 was designed before sound came about and doesn't have a way to handle this where the PSX is full electronic and can sense/learn the surge and compensate at start ups.

I don't think a capacitor would do any good, but I'm not exactly sure how you are suggesting the use. The way an incandescent bulb works is with a positive temp coefficient it acts as a near short around the PM42 at initial startup and allows the capacitors to charge. As the filament heats the resistance goes up and the current then follows the path of least resistance through the PM42. This, of course, is in milliseconds. Bulbs were commonly used in the early days for short detection and so on.

Ahh, I get it now!

I'll have to invest in the PSX4's then, slowly...

 

[RexHea]

Josh, one thing that I just realized with the light bulb arrangement is when there is a short the light bulb lights. This is caused by the PM42 tripping, opening the circuit, and then current flowing through the bulb, thus I still have track power.

 

[RexHea]

Ok, I finally found the article about this. This is well worth reading by everyone in DCC.
http://www.members.optusnet.com.au/nswmn/cb_sound_reset.htm

What it says is the amount of current still in the circuit will not do any damage if the short is immediately removed. Discussion on several different types of circuit breakers are included and it is well worth reading about. With the #1156 bulb limiting current flow, there is only ~1amp of current still flowing and it will flow only through the guilty wheels/axle and won't do any damage if corrected quickly.

 

[NYC_George]

Signal trouble

I also started installing signals Rex but I had to stop because of a different problem. It seems I made my signal bridges the same height as my fellow club members ebows. They knocked so many of my signal bridges down with their ebows that I had to take the bridges off the layout. I can't use drawfs because if a another train should pass you can see them. I could raise the whole layout but then the helix would have to change as well. So right now my signal project has stopped until I figure things out.

NYC_George

 

[RexHea]

Haha! George, that's the Godzilla effect!
I hope that I won't have much of that considering the high cost of the lights or the hard work in making them. Where did you order your light parts for the bridges? I have a couple from Oregon Rail.

So far, the biggest hassle I've had is the original wiring had one main bus running the layout. That's simple enough, but not when you have two other levels tied in to this same bus. I finally just shut the layout wiring down, disconnected the upper levels, and ran a new bus for the upper areas that won't have detection. The fun comes when I run all the detected sections...next . I am using the Digitrax BDL168 for detection and the SE8 for the signal drivers. Railroad & Company will control it all.

 

[NYC_George]

Block signals

Rex
The last batch of bridge signals I bought where Oregon as well. I have some tracks already set for blocks and just in case I change my mind on the system I drilled holes for light sensors. I haven't really decided on which way to go yet. I'm waiting to here from people like you and what kind of problems if any your having before I decide. I do want to run every thing in to a computer later. I get lots of request to see the layout. I can't run 6 trains at once by myself. Some time in the future I'll have to write some type of software program. First I have to solve this Godzilla problem. I'm thinking I'll make a flat concrete pad and then attach the signal bridge to a second tapered concrete footing. Drill a hole in the first flat concrete pad run a rubber band up through the hole and attach it to the tapered concrete footing and then back up the other side using the same method. The whole signal bridge will be on a rubber band spring. I'm thinking it will work. The tapered concrete footing will be able to move a little on the flat concrete pad attached by the rubber band. I'll let you how it worked at our next meeting.

Rex I hope you keep me posted on your project. Let me know how the Digital BDL168 is working out. Tony knows me extremely well. It's something I want to do in the near future.

NYC_George

 

[UP2CSX]

George, did you ever try attaching them with silicone? Might give them a little extra give. My signal system is easy but primitive. When a train goes by, I flip the switch to red. At some point in the future, I try to remember to flip it to green.

 

[RexHea]

George, I will certainly be making more posts as things progress. Always feel free to ask questions or even better...make suggestions. I am having to feel my way through all of this. The manual for Railroad&Company is 250 pages of hundreds of combinations you can use, so I have to try and narrow it down to what will fit the layout and how to set up the detection sections in a way that is logical.

The very first thing that happened to me was when I built the layout, I had no plans for full operations. As I began meeting more and more modelers and operating on other layouts, it then was a must. I had to first go into the layout and redesign areas, add sidings, and passing tracks. Then, and because I have two-way traffic on the mains, the need for signals became an absolute. So...here I am .

Jim, actually flip switches would be great if you had a full time dispatcher. That's a good idea with the silicone or maybe some kind of rubber like stick'um so you would have enough give. Of course, a baseball bat and a knot on the head works too!

 

[NYC_George]

Silicone or Stick'm

Thanks guys I'll try both. When we have our next meeting I tell everyone just be your Godzilla selfs tonight I have a test going on.

NYC_George

 

[Cjcrescent]

Rex
The last batch of bridge signals I bought where Oregon as well. I have some tracks already set for blocks and just in case I change my mind on the system I drilled holes for light sensors... First I have to solve this Godzilla problem...

George;

The way you've described your Godzilla problem, is corrected with a very easy fix, IIRC.

Obviously, the bridges are very close to the edge of the layout. I've seen pix in MR where guys have taken a strip of plexiglass or another clear fairly thick plastic, and cut them about 6" wide and 12-16" high. Then carefully drill screw holes thru the plastic and install them on the edge of the layout next to the signal bridge, with 6-8" of plastic rising above the layout edge. The clear plastic allows everyone to still see the signal, and the thickness of the plastic protects the bridges from "Godzilla"

A rough drawing of the concept is attached.

 

[John P]

Wayne Roderick, who's written about signals occasionally for MR, deals with the Godzilla problem on his railroad by mounting each signal with an integrated-circuit socket concealed in the base. That way if it gets bumped it can fall over rather than breaking. Though I have to wonder if the pins of the connector would be likely to get bent instead.

Here's a picture on his website:
http://www.tslrr.com/signal1.jpg

Edited to say that at our club, we don't fool around. We have plastic all around the layout, even if it "makes it look like the railroad is in an aquarium". But the plastic sheets are in slots and can be easily removed.

http://tmrc.mit.edu/progress/image.tcl?year=2007&month=4&day=13&image=IMG_4640.JPG

 

[NYC_George]

Thanks Carey,
I think that's a great idea. On train club night they go up. I just make they removable. Everyone else thanks for your imput.

NYC_George