Using an Auxiliary Transformer

[douellet]

I am building a simple shelf layout that runs around my computer room. I have two MRC transformers, one is 100 watts and the other 60 watts. I plan to use the 100 watt transformer to power my trains and the the other one to run a few accessories which will operate independently of track contacts. I have one pair of 022 turnouts which I want to power using constant voltage instead relying on track voltage. My question is, can I use the 60 watt transformer to supply the power to the turnouts without first phasing the two transformers? Thanks for any help.[:)]

[Big_Boy_4005]

Modern transformers may already be phased, if the plug only goes into the outlet one way, you should be in business. If not, phasing is a simple matter of flipping one plug around.

[Anonymous]

In short, yes you will need to make sure the transformer is properly phased. The aux power from one transformer will supply the hot and the common is supplied by the track from another transformer thus completing the circuit.

[jkerklo]

An auxiliary transformer for switch constant voltage is a good idea. I am assuming you are using O22 style switches, since the term "constant voltage" usually implies that switch type. I would recommend at least 14 volts, and 18 to 20 volts would not be too much. Nice snap at 20 volts.

The need for phasing for switch constant voltage is not as great, since the engine pickups will not routinely short the constant voltage to track power. However, the constant voltage does appear on the isolated rails used for non-derailment and a derailment at the switch can cause such a short (through either or both switch coils) and the risks of damage are less if it is phased.
Basically, just the right derailment can cause twice the voltage to be placed across the switch motors and the frog restrained so it is applied continuously.

Use an AC voltmeter to phase the switch constant voltage with the track power at the switch. (I have never been comfortable with the sparking technique.)

Mark the transformer plug and constant voltage connections.

A 60 watt transformer is OK for switch constant voltage. An O22 switch motor consumes about 2 amps, when switching, and only the light bulb when not switching. (Change the bulbs for whatever voltage you use. I replace all switch bulbs with 18 volts. Saves bulbs and lanterns.) Switching time is on the order of a second.

If you have a lot of switches and they need to be switched at the same time, then a larger transformer may be needed.


John Kerklo
TCA 94-38455
www.Three-Rail.com

[Chris F]

John, you may not need to swap bulbs. Based on Greenberg's PW manual, and on the manual I got with my modern O22 turnouts, the standard bulbs are already 18V - type 1445 (18V, 0.15A, 2.7W, bayonet base). If we include the two controller lamps, each switch would draw about 0.45 Amps (8 Watts) at 18V.

Although older O22's might require higher Voltage, I run mine at 14V. As you noted, operating a bulb at a Voltage lower than its rating will increase bulb life, and there will be less risk of melting the lamp when the bulb doesn't get so hot.

douellet, you didn't mention what other accessories you are planning to power with the 60W transformer. Your decision on where to set the voltage for the switches also will depend on the voltage requirements for the accessories. My newsstand/passenger station/hot dog stand operate frantically at 10V, while my windmill requires 16V to start moving. As a result, I've wound up with four auxilliary transformers (yes, all phased to the train transformer), set in 2V increments.

[douellet]

Thank you for the help. The layout I've built is very simple. It has a passing siding using a pair of 022 turnouts and it runs around an 8" by 11" room. I will only be running one train at a time. I have the following accessories: 133 station, illuminated platform, sawmill, rotary beacon, 3 street lamps and 2 crossing gates. I also have 2 older 40 watt transformers I can press into service. Should that be enough?

Maybe it's time to consider upgrading my power supply. I'm thinking about a MRC 270 watt unit. I'm not interested in anything fancy as the bulk of my locos are Williams and older Lionel, MTH and K-Line with out command control. Would this be a good choice?

I've had a lot of fun building this type of shelf layout. It's about five feet off the floor with a lift out bridge at the doorway, so I've still got plenty of room for a bed, desk, bookcase, etc. The best part is that the wife thinks it's cool, maybe because it gets most of my trains and railroad stuff out of the rest of the house.

Thanks again for the advise!

[Chris F]

The 133 station uses a #57 14V bulb and would consume 2.8 W at that voltage. The street lamps use a 12V bulb; I don't know the Watts but it shouldn't be more than 2.4 W each. The illuminated platforms have used various bulb types over the years, but nothing that should exceed 8W for both bulbs. Consider using one of your 40W transformers for these accessories. If you use a separate common wire (not connected to the track), you would not have to phase this transformer.

The crossing gates use a #363 14V bulb. I've found that the solenoid needs as much as 16 V to fully lower. Consider operating the gates with the same 60W transformer you will be using to power the O-22 turnouts. If you are operating these at higher than 14V, you can always replace the # 363 bulbs with # 1455 18V bulbs, the same as used in the turnouts. Another advantage to using the same transformer for the gates as for the turnouts is that is will already be phased to allow the use of insulated track to operate the gates.

The sawmill and the rotary beacon are a little trickier, and may require some adjustment. My modern sawmill operates okay at 12V, but vibrotor on my rotary beacon doesn't work well below 14V. That second 40 W transformer might come in handy here!

[douellet]

Thanks Chris for your advice. I like your idea of using the small transformers for the lighting. I've got my transformers phased and hope to start getting things wired this weekend. I've got to pick up more wire, terminal strips and a couple of Atlas connectors. I've read that color coding your wiring is the way to go, so I'll give it a try.