Comments on March CTT

[lionelsoni]

I just bought my copy of the March CTT.  I have some comments about two items.

In the "Questions-Answers" feature, Richard Ostovitz asked, "I have a relay-controlled block system to prevent rear-end collisions on my O gauge layout.  In the past, I've had no problems....  Now I'm attempting to run...with the new K-Line passenger cars, and the locomotive won't stop in the blocks.  Each truck on each passenger car gives power to the whole car, and the cars outside the block are bridging the gap between the insulated rail and the powered rail....  Is there anything I can do about this?"

The answer was, "The only remedy we can see would be to disconnect one of the rollers on each car, and power all the lights from the one remaining roller.  This will solve the bridging problem, but the lights will flicker on turnouts and crossings."

There actually is a simple solution whereby Richard can have his cake and eat it too.  It is to install two small bridge rectifiers (such as the Radio Shack 276-1152) with one ~ terminal of each rectifier connected to the outside rails (whether through the frame or from brushes on the truck) and the other ~ terminals connected each to one of the pickups.  Then connect the + and - terminals of both rectifier modules to both lamps.

A variation on this scheme, which I use, is to put an electrolytic capacitor across the lamps, to allow them to coast through any interruptions.  In fact, if the car has two pickups, I generally remove one entirely to reduce drag.  The lights can still go off if the trains stops with the remaining pickup not touching a rail; but the capacitor takes care of any flickering in motion with only the one remaining pickup.

The article, "Wire a more reliable Lionel signal bridge", by Dennis Eichenberg, is also concerned with a bridge rectifier and lights, but on a signal bridge rather than in a passenger car.  He describes correctly how to wire a control rail and a relay to operate a red-green color-light signal in place of a 153C contactor.  He uses the bridge rectifier to operate a DC-coil relay, and a capacitor to keep the relay operated through interruptions in the continuity from outside rail through the wheels to the control rail.

For his situation, where the common connection for both signals of a two-track signal bridge is the same, and where he desires the anti-flickering feature that the capacitor gives him, his is a very good solution.  However, for those who might have only a single signal and either don't have or can live with control-rail interruptions, there is an even simpler way to solve the problem.

Wire the green lamp to the track common, that is, the outside rails generally.  Wire the red lamp to the center rail or to the accessory voltage, whichever you are using.  Wire the signal common to the control rail.  Then wire another lamp in parallel with the red lamp, of similar voltage rating but at least twice the current rating, or just two lamps of the same type as in the signal.  For example, a 120-milliampere number-53 red lamp could be paralleled with a single 240-milliampere number-57 lamp or two more number-53 lamps.  You can hide this extra lamp, or make it some other lighted accessory, like a floodlight tower, perhaps on a distant part of the layout.

[Joe Hohmann]

I have a question concerning this issue. Why does the "1940's" layout article show a close-up photo of a '57 Ford?

[johnandjulie13]

As usual, great stuff, Bob.  CTT should hire you as a technical editor for these types of issues.  I like your idea of having a capicitor across the lamps.  What type of capicitor would you use?  I would love to eliminate the flickering of my passenger cars and my cabooses.

Regards,

John

[Dave Connolly]

 Joe, the trains and most of the opperations are based the 40's during the war. The auto's and trucks represent a few different eras. At times I'll take some 60's era trains off the shelf and run them.  As autos become available for the 40's I replace what I can on the layout. There are a number of them available but many are beyond my price range. I've got 41 Fords in every color as well as duplicates. Some scenes you simply have to use whats available.

[lionelsoni]

John, I use aluminum electrolytics.  I have a large stock of 16-volt 5000 microfarad ones that I salvaged years ago, so I use one or two of those, depending on how many lamps and how much current they draw--it's not critical.  Electrolytics tend to tolerate moderated overvoltage surprisingly well; but I would recommend to others to get a higher voltage rating.

Here's a Radio Shack link:

http://www.radioshack.com/product/index.jsp?productId=2102508&cp=2032058.2032230.2032267&allCount=111&fbn=Type%2FElectrolytic+Capacitors&f=PAD%2FProduct+Type%2FElectrolytic+Capacitors&fbc=1&parentPage=family

However, you can get them cheaper elsewhere.

[johnandjulie13]

Thanks Bob:

Just to make sure I understand, I would wire them in parallel with the bulbs?

Regards,

John

[lionelsoni]

Yes.  But you can do this only if you have put a bridge rectifier between the track voltage and the lamps, to convert the track AC to DC.  The polarity of the capacitor must match that of the bridge rectifier's output.  (For some reason, it is usual for only the negative terminal of an electrolytic capacitor to be marked, with a minus sign.)  If you have an older car the shells of whose lamp sockets are permanently connected to the frame of the car, you will have to replace the sockets, since neither side of the DC lamp circuit may be connected to the AC-circuit side of the rectifier.  Newer all-plastic cars are easy to rewire.

[Joe Hohmann]

 Joe, the trains and most of the opperations are based the 40's during the war. The auto's and trucks represent a few different eras. At times I'll take some 60's era trains off the shelf and run them.  As autos become available for the 40's I replace what I can on the layout. There are a number of them available but many are beyond my price range. I've got 41 Fords in every color as well as duplicates. Some scenes you simply have to use whats available.

Dave, I think your layout is wonderful, it's the 1940's title that set it up for "smart A's" like me. My layout is 1938-48 trains, but most of my cars, and some of my structures are 1950's. Cars of the 40's are tough, since they did'nt make any during the war years. The 1930's diecast ones they make tend to be "rich people's cars". Do you have any IXO '47 Fords? Nice cars, but can only be found on eBay now. I also have Franklin Mint's '49 Ford wagon, and Paul's Model Art '49 Ford convertable...both from eBay. Joe

[Anonymous]

Bob,
Which of the following diagrams illustrate what you are referring to?



Or



I couldn't quite make it out.

[jprampolla]

Hi Folks,     

      It is very important that an electrolytic capacitor be connected correctly in a circuit or it can explode resulting in bodily injury!  According to many Kalmbach books, it is best to use a capacitor rated at twice the voltage it may receive, at least.  Capacitors are wonderful when handled correctly.  It is not good advice to give a capacitor voltage over its rating.  Please protect your eyes and face when testing any of these circuits!      

     Take care, Joe.

[Bob Keller]

Seems to me that removing a pickup roller might be less complex!

[Anonymous]

Bob,
The problem was passenger car lights flickering when the car traverses a switch or crossing. The solution the manufacturers came up with was two pickup roller trucks. The problem here is that when the car bridges a block section the power is transmitted through the lighting wires and causes the block to be bridged. Yes removing a pickup solves this, but it reintroduces the flickering, so how do you resolve BOTH, that is what lionelsoni is attempting to solve.

[Anonymous]

Of course couldn't one simply isolate the lights to seperate pickup rollers?

If memory serves me correct most of the passenger cars have 2 or more lights... now the lights would dim when crossing a switch or crossing, but they would not go 'out' nor would the car bridge a block section...

[Bob Keller]

Please note I was using my Jack-in-the-box smiley face.

[Anonymous]

Please note I was using my Jack-in-the-box smiley face.

[lionelsoni]

Brent, neither!

I actually suggested several alternatives.  The first one is simply to solve the two-pickups-bridging-the-gap problem.  CTT suggested running the lights from a single pickup, which solves the bridging problem but reintroduces the flickering, as you pointed out.  Another approach that you mentioned is to power two lights separately from the two pickups.  I have some Williams cars that do that.  The flicker is still there, just split between the two lights.  Here is my fix again, in more detail:

Connect the wheels (or frame) and one pickup to the ~ terminals of one bridge rectifier.  Connect the wheels (or frame) and the other pickup to the ~ terminals of the other bridge rectifier.  Connect the + terminals of the bridge rectifiers together and to one side of the lamp circuit (all the lamps in parallel).  Connect the - terminals of the bridge rectifiers together and to the other side of the lamp circuit.  That's it--not too complicated I hope.  All the lights will be on whenever there's any voltage between the wheels and either pickup; but the rectifiers block current from flowing from one pickup to the other.

The next version simply adds a capacitor (or more than one) across the lamp circuit.  The capacitor acts like a small local battery to keep the lights on briefly even when there is no voltage from either pickup.

The last version, which I use, eliminates one of the pickups and its bridge rectifier.  The lights are then powered entirely by the remaining pickup through the remaining rectifier, depending entirely on the capacitor to keep the lights on over the voltage interruptions.

As for the capacitor, note that I recommended the 35-volt Radio Shack part, not the 16-volt freebies that I have been able to get away with.  A 35-volt rating should be able to handle as much as the 25 volts RMS that a type Z puts out.  If you run that high, you'll need to replace the lamps in the cars too...;-)

By the way, I see that Mouser has 35-volt, 4700-microfarad capacitors for $2.39, 10 @ $1.80, their part number 647-UVZ1V472MHD.  They have radial leads, diameter 18 millimeters, length 35.5 millimeters.

[Jumijo]

 

Is there nothing a bridge rectifier can't make work better?

[ben10ben]

I have been told that electrolytic capacitors shouldn't be used at a voltage significantly lower than their voltage rating, either, as the electrolyte can dry out and the capacitor becomes useless.

 

Would Bob or other folks on this thread care to comment on this?

I have some cars on which I would like to elminate the flickering, but if this is the case it seems as though the dozens of 600 volt rated electrolytics I bought for use in antique radios would not be ideal to use. 

Thanks,
Ben

[Dave Connolly]

 Joe, other than the mentioned 41 Fords your right. Not a lot available car wise for the war era. Pick up trucks on the other hand are pretty plentiful. I check out Die Cast Direct often looking for particular vehicles. Brooklin makes some great looking cars but way out of my price range.

 I  re did this scene a few weeks ago. The 50 Ford Police car has pulled over a 32 Ford done up more as a street rod. The new scene features what else. A 41 Ford cruiser and a Lincoln. I had to have something that at least looks like it could break the speed limit.

 Finding a car with a flat for that scene isn't a problem. I may look again and see whats offered as far as pickup trucks used as service vehicles. I seem to shoot that area often myself and it would look better with the proper era cars. The best part of all this is that in the future I may migrate to another era such as the 50's or 60's. I'll have some correct cars and trucks already stockpiled.

[lionelsoni]

I think they don't "dry out"; but rather they just lose their ability to withstand higher voltage, through some chemical magic.  However, they are easily "re-formed" by putting them into a higher voltage circuit.  They draw a leakage current at first, then straighten out and run like new.

Since high-voltage capacitors are bigger than low, I wonder whether you can get a useful amount of capacitance into a car with those 600-volt parts.

[Anonymous]

Thanks Bob for the clarification...

So this is what you were referring to?



The capacitor would simply remove one pickup roller and bridge rectifier combination, then add the capacitor to the + from the bridge rectifier to the lamp?

[lionelsoni]

Assuming that the yellow circles are the lamps, that's right.  (The lamps don't actually have + and - terminals--they can be hooked up either way.)

The capacitor goes in parallel with the lamps.  That is, the + terminal of the capacitor connects to the + side of the lamp circuit and the + terminal of the bridge rectifier(s); and the - terminal of the capacitor connects to the - side of the lamp circuit and the - terminal of the bridge rectifier(s).

[dmestan]

Bob, why is it necessary to connect the DC outputs of the 2 rectifiers together?  Couldn't they individually control their own bulb, or is this an added coverage for the flicker issue?

thx, Don

 

[lionelsoni]

It is so that the lights go out only if both pickups lose contact at the same time.  Consider all these possibilities:

Worst flicker:
One pickup, no rectifier, no capacitor, one lamp circuit--no bridging between blocks.
Two pickups, no rectifier, no capacitor, two lamp circuits--no bridging between blocks.

Moderate flicker:
Two pickups, no rectifier, no capacitor, one lamp circuit--bridging between blocks.
Two pickups, two rectifiers, no capacitor, one lamp circuit--no bridging between blocks.

Little flicker:
Two pickups, two rectifiers, two capacitors, two lamp circuits--no bridging between blocks.
One pickup, one rectifier, one capacitor, one lamp circuit--no bridging between blocks.

Least flicker:
Two pickups, two rectifiers, one capacitor, one lamp circuit--no bridging between blocks.