Middle Earth Model Railway

Two Capacitor Discharge Units (CDUs) are used to provide power to the point motors in the layout. One is for points at Grey Havens and the other for all the rest. The method of operating the individual motors varies between control panels. On some a button is used to trigger the CDU, while on older panels a metal stud on the panel surface is touched by a hand-held wire to complete the circuit.

In some cases a number of point motors are linked together for ease of use (e.g. in cases where the movement of one point must logically be complimented by the movement of another to prevent de-railments). This is where the CDU is vital as it is able to deliver the large current drawn by a number of motors working together. The basic 16 Volt supply from the transformer could not do this in many situations. Also, the output provided by the CDU is momentary preventing a continuous current flowing through the point motors, as would be the case if the 16 Volt supply was used. This prevents the motors from damage or burning out.

The main CDU has been modified by the addition of a third capacitor to provide more power to the motors. This is also to help with the problem of resistance in the cables carrying power from the CDU at one end of the layout to the other, which has been found to reduce the current reaching some point motors.