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Controlling Electro Frog Points

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In this application the a ‘Latching Relay’ is used to control the polarity of the Frog in a set of Points, also a local Signal or Status indication back at the control panel. The type of motor used in this circuit is a twin coil type with a momentary toggle switch to change the state of the points. As the switch, and therefore power to the motor and the ‘Latching Relay’ is only momentary, the ‘Latching relay’ is used to remember the status of the points.
 
The ‘Latching Relay’ is powered from the Power Supply via the Momentary Switch, as shown in the circuit diagram. Positive power is placed on either C1 or C2 depending which way the switch is pushed, this in turn pulls the Point motor Lever Left or Right which changes the state of the Points. Power is then removed from the Points and the MR204, but the contacts on the ‘Latching Relay’ remain in the last state they were energised to.
 
The circuit shows a wire from the RED track going to Terminals 3 of T2, and a wire from the GREEN track going to Terminal 2 of T2. The YELLOW frog has a wire going to Terminal 1 of T2. Because the Contacts in the relay are Changeover the Yellow wire will either be powered from the Red or the Green track. The other terminal set T1 can be used for anything – another set of Points, a Signal, Indication LED’s back at control, or to lock out another set of Points.
 
IMPORTANT. The drawing is powered for Straight Through therefore the power from the RED Track is running through the relay from Terminal 3 to 1 on T2. Because the Relay stays in the last state even when power is removed you must check the flow of power. (It could be that when you receive the ‘Latching Relay’ the relay is in 2 to 1 state in which case you would be putting GREEN power onto the Frog, which is not what you want.) There are two ways to solve this.
1) Place a positive pulse on either C1 or C2 to change the relay, independent of the Point motor. You do not want the points to move.
2) Swap the wires around in Terminal T2 (3 to 2) and (2 to 3
The same as above will apply to anything connected to Terminal T1.