Detailed information about the MRX1 and MRXP crossing signal controller circuits.

• Circuit board dimensions: 2.5 x 2.5 x 0.65 in.
• Control inputs -- Connecting an input to 'C' (0 volts) makes that input 'active.' Disconnecting an input makes it 'inactive.' Voltage = +5vdc, current less than 0.5ma out.
   
  The controller can operate in two different modes, Standard mode and Very Basic mode, an option for users using just one or two train detectors.
   
  Standard mode input functions:
  • FW - Upon initial activation, crossing lights begin flashing and gates come down. Further activation or inactivation of this input will be ignored. If no other inputs are activated, gates will open after 28 seconds, crossing lights will turn off and the controller will be reset.
  • MW - Upon initial activation, crossing lights begin flashing and gates come down. If lights are already flashing due to prior activation of FW, flashing time will be extended another 28 seconds. Further activation or inactivation of this input will be ignored. If no other inputs are activated, gates will open after 28 seconds, crossing lights will turn off and the controller will be reset.
  • NW - Crossing lights will flash and gates will be lowered whenever this input is active.
  • NE - Crossing lights will flash and gates will be lowered whenever this input is active. The order in which NW and NE are inactivated determines the direction which the train exited the crossing. The approach inputs from that direction will be ignored until they have been activated and then inactivated for 4 seconds. If the approach inputs are not activated after 45 seconds, the controller will reset and the approach inputs will be re-armed.
  • ME - Upon initial activation, crossing lights begin flashing and gates come down. If lights are already flashing due to prior activation of FE, flashing time will be extended another 28 seconds. Further activation or inactivation of this input will be ignored. If no other inputs are activated, gates will open after 28 seconds, crossing lights will turn off and the controller will be reset.
  • FE - Upon initial activation, crossing lights begin flashing and gates come down. Further activation or inactivation of this input will be ignored. If no other inputs are activated, gates will open after 28 seconds, crossing lights will turn off and the controller will be reset.
  • On - Activate to turn on flashing lights and lower the crossing gates. Takes precedence over all other control inputs except Off.
  • Off - Activate to open the crossing gates and turn off flashing lights. Highest priority of all control inputs.
  
   
  Very Basic mode input functions:
  Very Basic mode offers another operating mode for users who only use one or two detectors connected to inputs FW and/or FE. This mode is selected by connecting terminal MW to terminal ME with a jumper wire, and leaving terminals NW and NE unconnected.
  • FW and FE - Crossing lights will flash and gates come down as long as either input is active. When the first input goes inactive, lights will continue flashing and gates will stay down for up to 28 seconds, giving the train time to reach the second detector. Once the second detector has gone inactive, the gates will open, crossing lights will turn off.
    If the second detector is not activated within 28 sec, gates will open, crossing lights will turn off, and the controller will be reset.
  • MW and ME - Must be connected to each other only. Controller checks for this connection at power-on only.
  • NW - Not connected.
  • NE - Not connected.
  • On - Activate to turn on flashing lights and lower the crossing gates. Takes precedence over all other control inputs except Off.
  • Off - Activate to open the crossing gates and turn off flashing lights. Highest priority of all control inputs.
  
   
• Power input
  • P1, P2 - 8 to 14 volts AC or DC. Current draw depends on the crossing signals.
• Output to lamps (MRX1 only). All outputs are DC, polarity +/- is automatically determined according to the crossing signal wiring configuration. Max current 550 ma.
  • Tip - Steady on, for lights or accessories that do not flash.
  • R - Flashes alternately with L at 50/minute. Gradual on/off effect to simulate incandescent lamps.
  • L - Flashes alternately with R at 50/minute. Gradual on/off effect to simulate incandescent lamps.
  • Rtn - Common return connection for all lamps. A separate resistor must be wired in series with any LED signals. See installation instructions for details.
• Output to gate motor (MRX1 only)
  • M+, M- - 4 volts DC, up to 20 ma, sufficient for 1 or 2 Circuitron Tortoise™ switch motors to operate crossing gates. Five seconds for total up or down travel time. M+ is positive and M- is negative when gates are driven in the down direction. Polarity is reversed when gates are driven in the up direction. Gates begin downward travel 2 seconds after lights begin flashing.
• Control output
  • B - Pulled low to C via an open collector transistor when crossing signals are active. Can switch up to 20vdc, 90 ma. Useful for controlling a bell sound effect. If no crossing gate motor is connected to M+ and M-, B will stay connected to C as long as the crossing lights are flashing. If a gate motor is connected to M+ and M-, then B will turn off 8 seconds after lights begin flashing, about the time gates have completely closed. This imitates common North American railroad crossing signal practice.
  • C - Common (0 volts dc) connection for control inputs and output. Do NOT connect signal lamps or motors to C.

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