I am having problems with the reversing relay circuitry. The relay has a tendency to stick. Anything short of beating on it fails to make it work properly. Does anyone have information or a schematic for this unity?
joelg
joelg I am having problems with the reversing relay circuitry. The relay has a tendency to stick. Anything short of beating on it fails to make it work properly. Does anyone have information or a schematic for this unity? joelg
I don't have an MRC CM20, but in building my own walkaround throttles I invariably installed 12VDC DPDT latching relays in the base unit for direction control. I am willing to bet that's what MRC used. Relay contacts should be rated for max track current of the unit.
There were/are 3 reasons for using a relay for direction control. It reduces the wire count in the tether by one. Controlling the relay is a low rated SPST switch instead of a DPDT which must switch full train current. And finally, with a relay for direction control, only control current goes through the tether. Track power is restricted to the output side of the base unit under the layout. This allows thinner wire in the tether with little to no concern about voltage drop. These advantages allowed me to use decent-looking, cheap, functional, readily available, coiled telephone handset cords for tethers for my handheld throttles.
Fred W
fwrightjoelg I am having problems with the reversing relay circuitry. The relay has a tendency to stick. Anything short of beating on it fails to make it work properly. Does anyone have information or a schematic for this unity? joelg I don't have an MRC CM20, but in building my own walkaround throttles I invariably installed 12VDC DPDT latching relays in the base unit for direction control. I am willing to bet that's what MRC used. Relay contacts should be rated for max track current of the unit.
Joel
Thought about my answer some more. Whether or not a latching DPDT relay is needed or not depends upon how the relay is actuated. In my throttle, I used an SPST switch to turn the relay on or off, thereby reversing direction. In that case, you want a non-latching relay.
If a momentary switch is used to cause the direction change - push button or spring toggle - then a latching relay is needed.
To determine what you have measure the input voltage at the relay and then change direction with the controller. If the voltage blips you need a latching relay. If the voltage stays steady in one direction, but reads zero in the other, it's a non-latching relay (most likely).