Lift Bridge and Dead Track

GunrunnerJohn,

In another thread on PTC's and Coach cars, you recommended this PTC 60R010XPR at Digikey

Would you recommend the same in this application?

Thanks!

Ron

As Columbo would say..  one more thing.. It's the darn pass cars rollers straddling the center rail insulated gap. You might as well hold a wire on one side of the insulated joint and hold it to the other side.  There's no fix other than to modify the rollers as John pointed out. (or completely disconnect one roller).  

On a similar  note..  With dcs we have a similar problem when a train is straddling 2 different  tiu zones. It's a signal problem and not a power related problem. 

That one was selected primarily to protect the wire in the case of a derailment.  To address this issue, I'd probably go a little lighter, since most of my LED upgrades only run in the 20-40ma range for power consumption.  Here's a 50ma hold, 100ma trip PTC that would be good for this application.  You could even go lower a bit.

I hasten to add, this only works if you have low current lighting in the passenger cars, if you have incandescent lighting, the size of the PTC would probably have to be large enough to allow the engine sufficient power to keep running.

There is a simple relay solution,no need to modify cars,though the fuse in them is a good idea. Anyone wanting a relay solution can Email me privately.

Dale 

Dale, why in the world would you not want to share it here?

Heck with the bridge. lets see a video of the whole layout.

Don't go 50.    

Heck with the bridge. lets see a video of the whole layout.

Flattering... but that area by the round house is the most completed area... and it's no where as good as some of the true modelers here.  We did some roads and I'm working on a Dairy area where trains and trucks can exchange Milk.

Thanks!

Ron

The same instantaneous results as with the auxiliary tender could be duplicated by always running a few unlit head end cars.  Pretty typical of most passenger consists and provides a positively dead circuit.  The initial hit and miss results can't be good for delicate electronics not to mention the damage from arcing.

Bruce

Brwebster... That is a good idea.  We have some rolling stock that we can add to create that spacing.

In the mean time... Here is another test.  This time the difference is a piece of electrical tape on the lead pickup roller of the 1st coach car.

That's the single roller with LED lighting.

Of course, with the capacitor and LED lighting, no flickering, even with one roller.

  Last words of last video." I wonder why?"  You do realize that there is a wire inside most pass cars the goes from one roller to the other roller? putting the tape on the roller is the same as cutting the wire in half.  The tape is an easy fix providing it'll stay on there.

Last words of last video." I wonder why?"  You do realize that there is a wire inside most pass cars the goes from one roller to the other roller? putting the tape on the roller is the same as cutting the wire in half.  The tape is an easy fix providing it'll stay on there.

LOL... Yes Gregg.  Just a poor attempt at sarcasm on my part.  I was planning on expanding the video to show the tape, but it was getting late so I just took a photo.

Ron

I kind of thought you did.  Are you leaning towards a  fix?

The sun is out, skies are on plane, low winds, Still below zero though . I'm out of here.

You can separate the rollers with a bridge rectifier,shown 

here

Dale H

 I will try posting this here,if it gets deleted it gets deleted.Click on any diagram to enlarge.

On an isolated rail on the approach to a lift bridge the rollers on the engine and cars jump the center rail via the pickup rollers and the train fails to stop in time when the bridge is up.  The bridge has an internal switch which shuts off power to the approaching block to the bridge. Here is how a relay can solve the problem and insure reliable voltage cutting. The relay coil is activated by the insulated rail method. The contacts are used to insure a shorter stop. The method is explained in more detail here

Here

The train wheels complete the circuit to the relay coil,converted to DC by the bridge rectifier. The capacitor 470 uf , 35 volt eliminates chatter caused by intermittent wheel contact and increases pulsed DC current to 24 VDC filtered. A 10 ohm half watt resistor in series to the capacitor slows charge just a bit to remove arcing. A 1n4001 diode across the coil suppresses spikes.

 When the train or any car sits on the outside insulted rail, the coil is energized working the relay contacts. When the relay is energized C (common contact) and NO (Normally open contact) are connected.When the relay coil is not energized C and NC (Normally closed contact) are connected.

So,lets say the bridge is up and B1 center block has no power. As the train approaches B2 still has power. When the wheels on the engine crosses the outside insulated rail, the relay is energized. B2 is disconnected from the track power and connected to B1 and share whatever power is on B1. Since the bridge is up both blocks B1 and B2 will not have power. If Block B1 is maximum stopping distance and block B2 is longer than the train,there will be no roller jumping. When the bridge is closed,power is restored to both B1 and B2. Power is cut off as soon as the first to metal wheels of the engine sits on the outside insulated rail. Thus stopping time is greatly reduced. The wheels and track have to be reasonably clean for this to work. Stopping distance depends on the type of engine etc. Pw stuff can coast a while.

Stopping distance can be further reduced with the addition of a second relay. This assumes only one train runs on the loop. The voltage can be reduced and the train slowed on the bridge approach. It will also start at the reduced voltage reducing wear and tear on the engine.

In this diagram the A throttle and D throttle run the train,the A throttle is set at a reduced voltage. When a train is on outside insulated rail IR2, the reduced power from "A" tap is on the train instead of the power from D tap. Note,both A and D are isolated and can not be connected together. Either A or D controls the train but not both. Without a relay A and D could be connected by roller jumping and cause damage to the transformer.

Shown is a PWZW,but any transformer with an accessory tap can be used. 12VDC relays can be used at reduced voltage. Just remember the capacitor increases voltage 41% so do not exceed 12VAC for coil power.  (that turns into about 17VDC)The 10V tap of an MTH Z4000 for example is appropriate.   Most relay coils can take up to 50% over rated voltage but why push it?  The contact rating should be 10 amp or more for track switching. I can not cover all the types of relays,there are too many makes and models. If you use DPDT ones,you can use the extra contacts for block signals etc. A good  24VDC DPDT relay and socket can be had for about $8. You can even get them cheaper if you want to do a bit of soldering.

If you are using a transformer with only 1 track output, you can make and use a voltage dropper to take the place of A and D taps.  2 bridge rectifiers for example can drop voltage by about 3 volts and reduce voltage on the approach. This same method can be used to slow a train down a hill or on a curve,wherever you need.

Dropping voltage with diodes is described here further

here  2

Further examples of circuits where relays eliminate roller jumping are here

here 3

here 4

Making the above circuit should cost about $20 or less. 2 relays,2 bridges and some misc parts. A euro style barrier strip will neaten hookup.  Use #22 wire or thicker for the coil circuit. Use #18 wire (short runs) for the track power circuit. #16 or #14 for longer runs.

Now someone wanted a bi directional circuit. He uses a Z4000 MTH transformer so we will use the 10 volt tap for relay power. It shares a common with track power internally with the transformer.  First we will have to establish direction logic. It can be done with conventional relays shown here for a crossing gate.

here gates

However this circuit does not have memory as a twin coiled latch relay does.For the crossing gate,after the train runs the loop once the system corrects itself. However this is about collision avoidance so we want to be right after power is shut off and restored.

For this circuit we will use a twin coiled latch relay. This will orient the contact switching in relation to train direction.

Here is a 12 volt DC  version for someone using the 10 volt tap of a  a Z4000 transformer. For a PWZW, KW etc, 24 volt DC ones could be used.

relay mouser link

Use of the relay is shown in detail in a different application here,some soldering is required to the relay pins,they are PC mount.

link

Below is the coil circuit using the relay. It is activated by the outside insulated rail method IR3 and IR4.They are placed at least one train length apart from the bridge where the train has to travel in order to cross the bridge from each direction. It assumes the train is not backed up across the bridge before it activates the following IR. ahead If 2 trains go the same direction and follow each other ,this system would have to be switched off in the proper orientation.

 A diode off the 10 volt tap provides DC rectification. capacitors remove ripple and charge voltage to peak. 10VAC becomes 14 VDC,filtered. A train traveling counter clockwise would leave the left coil thrown. A train traveling clockwise would leave the right coil thrown.Insulated outside rails IR3 and IR4 need only be 1 section long. The coils will take continuous power if the train sits on the IR. In this diagram 2 SPDT  relay coils are wired in parallel to get an effective DPDT one.

Below that are 2 SPDT conventional type 12VDC coiled relays which are activated by outside insulated rail IR1 and IR2. The next diagram shows the switching,it is similar to the unidirectional circuit previously described except 2 relays are used. The contacts orient the switching as to train direction. Hope I got it right,you can trace circuit flow to verify.

Connections can be made with a barrier strip and some soldering to the relay pins. This whole thing could be made up for maybe $30-$40 depending on how cheap you can get components.

Dale

Dale, why in the world would you think it would get deleted?

Dale, thanks for taking the time to post the circuits; lots of solutions for a variety of requirements.

Yes.Thanks Dale H.

Hello John

I don't want to go into it too much and get the post deleted. First the webmaster posted a rant,now deleted,which advised topics should be put in the proper section. This is an electrical question and it is in the general forum. Second,I was told not to link directly to my blog. There I explain electrical concepts,I don't sell anything.There is enough information there to automate a layout to museum quality. I try to share what I have learned freely.   If I did not link them and copy and pasted everything instead,it would make my post very wordy and redundant. I try to make things as simple as possible. You are an EE and understand electricity better than me or most people, I am only a retired pinball machine repair man and instrument technician. I see things perhaps differently than you.  But you have to remember there are some readers who are not that well versed in electrical concepts,so I have to add extra explanations,so as not to lose the average reader. I do lose most of them anyway but I try best I can. 

Believe it or not I was diagnosed one time in school as retarded,and have had struggled with dyslexia all my life. Now I am accompanied with other problems like migraines. It is difficult for me and collect my thoughts where my writing is comprehensible. It is disappointing when my threads just arbitrarily disappear,so I post much less now so as not to waste my time here. I got quite a few Emails on this topic so I made up this post to hopefully explain the concept to anyone interested. I do this type of thing on my totally automated layout with success,my methods work as long as the track is kept clean. I never jump rollers or parallel transformers. 

  Nothing against Forum members here who I respect and hold in high regard. I shall continue to visit and read here,but I will no longer post much. Often the same questions are asked over and over so linking posts from my blog is a helpful way to explain things. I invite people to go there and feel free to Email me with any questions. My knowledge is mostly about conventional operation but some of my circuits,such as block detection can be useful to command users. Best wishes to all of you Forum members and thank you for the kind comments.

Dale

Dale I appreciate the reply, and I didn't realize this was a problem, thanks for pointing it out.

I think your contributions are very valuable here, and you do go that extra mile to make it simple for the non-electrical types.  I'm sorry that you have been partially chased out.

Thanks all for the thoughts and ideas.  You have me thinking for sure.

Ron

Thanks, dale for using your words and pictures to clearly explain something I couldn't manage to explain.  

Very good post.