LONDON GARDEN
RAILWAY SOCIETY
The LGB, EPL System
By Greg Brown
The EPL system is comprised of the following basic components:
12010
Switch Drive, which is a DC motor and by way of a rack and pinion gear,
drive the turnout right or left.
12030
Supplementary Switch, this is a double pole double throw switch which
can be added to the switch drive and can be used to activate or power
track sections or accessories.
17100 Track Contact, this is a reed switch which closes when a magnet goes over it and with the use of diodes produce the positive or negative voltage required for the Switch Drive.
17010 Magnet, this is attached to the bottom of the locomotive to activate the track contacts
51080 AC Transformer, 18 Volt AC, ˝ amp, this provides the power for the EPL system.
To understand how this system works requires a very basic knowledge of electricity. The switch drive is a DC motor with a gear on the end which moves a lever in or out. Like your train motor the polarity of the DC voltage, positive or negative cause the motor to go forward or backward, or in and out in the case of a lever.
AC voltage can be converted into a DC voltage by using diodes and depending how the diodes are arranged it can be a positive or negative DC voltage. In the case of the Track Contact one terminal produces a Positive voltage and the other a Negative voltage.
By colour coding our wires we can establish a wiring convention that will prevent crossed wires, which is a bad thing. Use one colour to signify our AC common line another colour for the AC Hot line and a third colour to signify the DC voltage line. On the AC transformer we will designate one of the wires as a common wire, (say the green wire). The other wire we will designate as Hot AC, (say the red wire).
The Switch Drive has 2 terminals on it, the left has a white circle and the right terminal has an orange circle. The Common wire (green) goes to the Switch Drive terminal that has a white circle. We can now daisy chain this wire to each of the switch drives that we are using and to any accessories that are powered by the 18 volts AC.
The Track contact has 3 terminals the centre one is a circle and the 2 outside terminals have a triangle of which one points up and the other points down. The Hot AC wire (red) goes to the centre terminal on the Track Contact designated by the circle. This is also daisy chained to each of the Track Contacts and any 18 volt AC accessories you may have installed.
A third wire is required and this will be our DC voltage wire, let’s say we use a blue wire. This wire is connected to the Switch Drive’s other terminal the one with the orange circle. The other end of the wire is connected to the Track Contact terminal that has a triangle. The Track Contact has a triangle that points up, this is the positive DC voltage. The other triangle that points down is the negative DC voltage. A positive DC voltage moves the Switch Drive lever outward and a negative voltage moves the lever inward. Determine which way the switch drive must operate and connect the red wire to the appropriate terminal. Test the drive if it goes in the wrong direction hook the blue wire to the other triangle terminal on the track contact. Since the Switch Drive requires 2 Track Contacts to work, the blue wire is then connect to the opposite triangle on the other Track Contact Only two terminals should be used on each Track Contact, the centre one and only one of the triangle terminals.
Below is a diagram on how to wire the Track Contacts to the Switch Drive. In this configuration the train will go around the track using the mainline on the first pass and on the second pass will go into the siding, then use the mainline and will continue to alternate routes.
2 Track Contacts are used for each Switch Drive. The Switch Drive can have 2 blue wires connected to the orange terminal as one wire will go to a Track Contact triangle terminal pointing up and the other wire will go to a second Track Contact triangle terminal pointing down. Another wiring method is to connect one Track Contact to the other then to the Switch Drive. Make sure that the wire on one of the Track Contacts is connected to the up triangle and the other to the down triangle, then to the Switch Drive. This may sound like we are crossing our wires but you must remember that the Track Contact only produces a DC voltage which the train magnetic is physically going over the Track Contact.
When a train approaches a turnout it either follows the mainline or goes into the siding, depending which way the turnout was set. When leaving the siding or approaching the sidings the turnout does not have to be moved, as the train engine will force the turnout into the right position. When installing the Tack Contacts they must be located far enough downstream so that the last car is clear of the turnout.
The next component of the EPL system is the Supplementary Switches for the Switch Drive. This is a set of double pole double throw switches that snap into the head end of the switch drive. A double pole double throw switch is a fancy way of say there are two switches (double throw) with a on – on position (double pole).
Double Pole, Double Throw Switch
With the use of track insulators the switches can be used to kill power in one section of track while applying power to another section of track. The contacts can also be used to turn lights on in a station when the train arrives and turn them off when it leaves. The Switch Drive does not have to be connected to a turn out, it can be used on its own with the supplementary contacts and now you have a relay that is controlled by Track Contacts and can be used to turn on and off accessories as the train approaches and leaves an area or diorama.
The Supplementary Switches have 6 terminals on them, since it contains 2 switches the top 3 terminals are for one switch and the bottom 3 terminals are for the other switch. The centre terminal in each group of 3 terminals is the common contact. Depending whether the lever is in or out, the centre contact will be connected to the inside or outside terminal.
Below is a diagram showing how to use 2 trains on one track. One train sits on the siding and the other on the mainline. Track power is alternately switch between the isolated track sections on the mainline and the siding by using the Supplementary Switches on the Switch Drive.
The brown wire represents track power. The centre terminal of the Supplementary Switch is connected to the inside track. An inside track in the siding and on the mainline have been isolated and each is then connected to one of the other terminals on the Supplementary Switch. Test to make sure that when the turnout is set for the mainline that the siding section is powered and the mainline section loses power. If this is not the case switch the inside and outside terminal wires.
The Track Contacts are place before the isolated section of track and far enough from the turnout so that the last car is clear of the turnout before it switches. The isolated section of track should be about 12” long as the train can coast a fair distance. To control track power we have only used one of the two switches, the other is free to be used to connect track signals or other accessories.
Here is a link to a You Tube video that shows the operation of the Switch Drives and Supplementary Switches and how they can be used with multiple trains. He has added some lights and blade switches so that he can turn the switch drives on and off.
http://www.track2.com/ingram/pic+vid/index.pic+vid.shtml
There are many web sites including the LGB site that show how to wire up different configurations but they are sometimes confusing. You should now have a basic understanding of how the EPL system works and the drawings should now make more sense.
Questions and comments can be directed to
