Millstonemike :appl: :appl:,
Is there another post somewhere that details the electronic parts you used in the diagrams above and where they might be purchased. Also, could you explain how the two different electronic diagrams connect?
Hi Chuck, that design was streamlined and improved and can be seen in the video below. Watch the switch in the right foreground circa the 28 and 53 sec. marks.
This circuit was designed for Marx switches. Marx switches do not have any inherent self tending capabilities. They simply have two "back-to-back" solenoids with a common pole. And the solenoid connections are isolated from the track. The manual push button control for these switches can be used in conjunction with this circuit and both will operate independently. This circuit will not work for switches with motors requiring reverse voltage to throw the switch to the diverging route I believe it can be adapted to that requirement..
Components (Per Switch):
One 12 V Delay Relay Module LINK
; One Adjustable Linear Regulator LINK
; One 1000 uf, 35 V Capacitor LINK
; One 510 Ohm Resistor LINK
; and Two 1 Amp Diodes LINK
The system was streamlined by adding two diodes in the isolated track trigger circuit. These diodes keep the isolated track sections electrically isolated from each other thereby eliminating the need for a separate regulator/delay module set for each route.
Modification 2 (untested):
The schematic below shows a 12 V linear regulator and a 12 V time delay relay. I originally used the 5 V versions of both as shown in the video. However, the 5 V delay relay module has a problem triggering the relay control circuit. When fed with 5 V from the linear regulator, losses in the relay module's onboard regulator and subsequent output of the 555 timer do not have enough voltage to trigger the relay's transistor control circuit. I solved that by replacing a blue SMD LED (4.8 V drop) with a red LED (2.4 V drop). But I don't recommend that unless your experienced with modifying SMD PCBs. Hence, I recommend the 12 V version. However, I have not tested this. Not to worry, there are workarounds if the 12 V version exhibit the same issue.
You could try the 5 V version by adjusting the regulator to 5.5 V to 6 V. That will likely solve the trigger control issue and should not materially shorten the life of the relay coil. And that might be better than the 12 V version given resistor/ capacitor sizing. For me it was easy as I have a parts box with various components for testing. DOH me, I should have tried increasing the regulator output before modifying the 5 V delay module.
Theory of Operation:
The relay module uses the normally closed position for accessory power to the common pole of the switch solenoids. When a train crosses an isolated track section, it completes the circuit energizing the corresponding switch solenoid to move the point to the correct position. It also completes the circuit powering up the linear regulator and, hence, the delay relay module. Thus, the delay relay module begins it's timer function. At the end of the adjustable time, it trips the relay into the NO (normally open) position. That disconnects accessory power from the common (center) pole of the switch solenoid (I have it adjusted for ~ 1 sec). As long as the train is on the isolated section, the relay will remain powered in the NO position. That prevents solenoid burnout.
You can park a train on the isolated section and the relay will remain in the normally open (e.g., triggered) position thereby protecting the switch solenoid. There are two LEDs on the delay relay module: The first (RED) indicates the module has powered up. The second (Blue) indicates the time has expired and the relay has tripped. You can see this In my video. However, there are two red LEDs because of modification 2 (above).
The diodes are used to prevent one isolated section from connecting the other. The capacitor is used for holdover - to prevent transients / intermittent contact of the isolated rail from restarting the sequence. The resistor is used to draw down power to quickly reset the system once the train has passed. Both were sized for the 5 V version in the video. If you run long passenger trains and/or very slow speeds, you must insure the the isolated section remains triggered as the train passes. For example, don't use a 3 " isolated section with 21" passenger cars lest the isolated section contact is broken in the middle of each car's trucks.
I'm in the process of moving to a new house. All my equipment is packed - trains and electronics. It would likely be months before I could a actively aid debugging on a live circuit. Though I will be online except for a few days in early Jan.
A picture of my unit with some