Signaling for the Lovelock section

The Lovelock section of the layout is connected to the main line by a turnout at the bottom of the helix.  The helix already has signaling controlled by an occupancy detection circuit.  I want the new signal and both of the existing signals to monitor the position of the turnout as well as occupancy of the helix.

To accomplish this I used a diode matrix type of technique.  Refer to the drawing below.  The two diodes that are in parallel with the relay coils are just there to suppress back EMF when the relay opens and don't affect the logic of this circuit.  The two diodes that are on the input from the detection circuit isolate the two relays from each other and prevent the 12 volts from the tortoise contacts from reaching the relay 

The use of a Peco insulfrog turnout at the bottom of the helix means there is no frog to route power to.  This left both sets of contacts on the Tortosie switch machine available to control the signals.  Referring to the photo below, +12 volts DC was connected to both commons (red wires).  The orange wires are connected to the position contacts.

This is the new circuit board to control the new signal.  The red and black wires are 12 power, the orange wire is from the Tortoise motor contacts, and the yellow wire is from the occupancy detection circuit.  The red and green wires are the outputs to the signal.  Notice the diode on the board between the terminals where the orange and yellow wires are terminated.  This diode allows the occupancy signal on the yellow wire to activate the relay but blocks the turnout signal from affecting the relay on the board for the helix signals.

At the board that was already installed to control the signals at the top and bottom of the helix, the diode was placed in line on the wire that connects it to the detection circuit.  This diode will prevent the signal from the orange wire on this board from affecting the relay on the new board.

So here's the new signal on the Lovelock siding.  It will indicate a red whenever the helix block is occupied OR the turnout is aligned to the staging yard.

And here is the same signal showing a green when the turnout is aligned to the lovelock siding AND the helix block is clear.