Adding an Amp Meter for Transformer (Part-2)

Classic Toy Trains Forum
1

I posted last year about adding a couple of amp meters (ammeters) to my layout that uses Lionel KW & ZW transformers.

I’m currently doing some rewiring on my layout because I had the common terminals of both transformers connected together (based on some recommendations that I read about 20 years ago when I was building my layout).

The recommendations that I received from that post was to separate the common (“ground”) connections so that each ammeter would be connected to the common U posts of the corresponding transformer.

I also had the ZW transformer powering the turnout switches on two separate tracks, one being used for command control and the other for conventional post-war engines being run by the KW transformer.

So I am separating that connection as well, so each transformer is running its own turnout switches and accessores, and have separate common connections.

I am using the KW transformer for conventional (non-command controlled) track, turnout switches, and a couple accessories).

The ZW is going to be used for command controlled track, switches, and the four turnout switches on one of the tracks, various lights, and accessories.

My dilemma now is that the KW transformer has a fixed 14 volt connection, using the C-D posts for the four turnout switches on the conventional track, and a couple accessories and some lights.

I’m not sure exactly on the wiring to the turnouts and accessories…

I assume either C or D post can be used as the “common” (and the other being for the power ("hot)) ?

The turnout switches are the modern (purchased in the last 1990s) 3010 & 3011 (70-3010-250, 70-3011-250) switches.

I’m not sure how the proper 14v fixed voltage gets wired to the turnout switches, since there is a common (ground) connection running to the track, and the power connected to the “hot” C or D KW post… I think if I connect this way, I will only get 6v, no

2

Ok so I was looking at a KW operations manual that I found online, and it looks like I should be using the D-U (fixed 20v) posts for the turnout switches and the C-D (fixed 14v) posts for the lights and accessories.

The D-U measures at about 18v and the C-D about 12v on my volt meter.

I’m not sure if the C-D posts could actually be used for the turnout switches, since the common U (ground) post is used on the track going into the turnout switches, unless insulated pins are used ?

So I’m still wondering if the ammeter that will be connected to the common U post will be registering the usage of the C-D connected lights and accessories ?

3

No it won’t.

And if you are using a common ground, there is no way to get at that 14 volts for switches unless you use A-U for trains, and B-U set to 14 volts for the switches.

4

Thanks Rob… That’s what I figured, but needed to know for sure… now I can continue my rewiring.

Ken H in OH

5

Well, I think the dilemma continues concerning using the KW transformer with my O31 switches…

The D-U connection that is giving a little over 18V is more voltage than the O31 switches can handle according to the instruction manual, that states “you must power the switch through the auxillary power terminal with 12 volts alternating or direct current” followed by “IMPORTANT: Do not continuously apply more than 14 volts alternating or direct current to the switch (either via track power or through the auxillary power terminal) or your switch may be damaged. Your power supply must have a circuit breaker rated at 8 amps or less.”

I did have the O31 switches connected to the D-U 18V+ to use the auxillary power instead of track power… the lights had a high glow, and were getting hot, so I looked into the proper voltage and discovered that the 18V+ was too much.

Evidently the old 022 switches could handle the 18-20v from the D-U connection ?

It looks like I have to use track power instead of the auxillary power for the O31 switches if I want to use my KW transformer, correct ?

Is there a way to reduce the 18V+ power coming from the D-U connection to a more suitable 12-14V if I want to use the O31 auxillary without modifying the transformer itself… something I can connect between the KW transformer and the power wires going to the O31 switches ?

6

AirM,

First - here is an old thread about the switches you say you are using above.

http://cs.trains.com/ctt/f/95/t/170101.aspx?PageIndex=1

(the ipad has refused to allow a pasted CTT forum link to workthe last day, so if the link does not work copy and paste it)

One thing that is confirmed is they operate at a lower voltage. However, even at the higher voltage of 19 vac, as long as you are not holding the voltage on the coil it should not heat up much. Even an 022 coil will smoke at a continuous 16 vac if a train becomes stuck/parked on the non-derailing insulated rail.

I think your issue with heat may have been the lamp operating at 19 vac. My old 022’s melted some of the lanterns (even with the vent hole) at 16 vac until I replaced all the lamps with LED (screw and bayonnet as appropriate) bulbs from Town and Country hobbies.

Personally I think you should use a variable voltage for the 3010/11 switches set to 13 vac. Use the U term for common and phase the transformers together if the tracks interconnect.

You can get a lower voltage off the fixed terminals of a KW as indicated in this chart, but your variable outputs are seriously reduced.

http://pictures.olsenstoy.com/cd/transfmr/ps6.pdf

7

Only for the bulbs if the switches are working properly.

8

Hey guys, thanks for the replies !

I failed to mention that it was the control lever switches that were getting hot from the bulbs being so bright… I don’t think the switches themselves were getting hot, maybe the bulbs, but I didn’t check them… my eyes and hands were drawn to the controllers, which made me look up the recommended voltage in the O31 switches.

I am using the B variable power KW connection, but only for a short stretch of track that I have “bumper” stops on each end, and use various “bumper” cars on… but I could easily just connect that to the A variable power with the main track that I am running… then use the B variable post for the switches.

My other transformer is a ZW… I use it for two other tracks that run TMCC, one being strickly command control with my GP9, and the other is a conventional 736 using the TMCC power master… and I used the other two variable posts for track switches, lights, and accessories.

The 5 amp ammeter that I have connected to the ZW is registering more than 5 amps, so maybe I do need the 15 amp ammeter, or maybe a 10 amp ammeter ?

What is the typical amp draw for a ZW transformer ?

Ken H in OH

9

0-14 amps.

10

Thanks Rob… glad I still have the 15 amp gauges that I started with… I’ll swap the ZW 5 amp for the 15 amp gauge.

11

So what is the typical amperage draw for a KW transformer ?

Is there a listing of amperage draws for the old Lionel transformers ?

12

KW would be 0-10 amps.

Most of the information is contained in the service documents.

13

Thanks Rob !

I did see a page that showed all the transformers and the voltage for the various connections, but the amperages were not listed in those charts… I need to update my notes !

I swapped out the ZW 5amp with the 15amp… much better !

Ken

14

A way to reduce voltage while maintaining regulation that I have described many times is anti-parallel diode pairs, which drop roughly a half volt each when wired in series between the transformer and the load.

An anti-parallel pair of diodes is just two diodes in parallel, but with the cathode of each one connected to the anode of the other. There is a trick to make two such pairs from the four diodes inside a bridge rectifier module: Just connect the + and - terminals together. Then you will get a drop of about one volt between the two ~ terminals, with the + and - terminal node providing a center tap if you need a fine adjustment.

15

When supplying turnouts or other accessories from the track common (outside rails) and a separate transformer, there is no need to have that separate transformer in phase with the transformer supplying the train. In fact, connecting it out of phase is slightly better, because the return currents in the outside rails cancel each other rather than add.