Hi Tony's, I recently bought a Digitrax BXPA1 auto reverser with an opto isolated switch to connect to the Jack AD Sensor that I also have recently purchased.

I was able to get the Jack Discrete to work with my PSX-AR to generate loconet messages that shows when the block is occupied and not occupied. But I can not get the opto Isolated switch on the BXPA1 to close when the block is occupied and open when the block is not occupied.

The BXPA1 generates a loconet message "BXPA1 (Board ID 12/16)Power Status Report Normal" when the loop is not reversed, and "BXPA1 (Board ID 12/16) Power Status Report Reversed" when the reverse loop is reversed. But there are no messages concerning block occupied status.

    The Digitrax tech bulletin on the BXPA1 states the following:

    • Opto Isolated Detector Output
    • Connections between the ON and OP terminals of the BXPA1 allow for external triggers when the detection section of the BXPA1 is active.
    • When the detection section is occupied the ON and OP connections will conduct and turn on the circuit.
    • These terminals are isolated from the rest of the BXPA1 circuits.
    • On the 8 pin connector, Pin 7/OP is the collector of OPTO NPN transistor, Pin 8/ON is emitter.
    • If Pin7/OP is at +5V then Pin 8/ON will conduct to a grounded 20k resistor on Pin 8/On.
    • This resistor can be the input of another PCB.

    I have made the appropriate connections to the Jack Discrete, but no block occupancy messages are generated.

    I have contacted the Digitrax tech support, but as yet they have no solution.

    Do you have any experience connecting a Jack Discrete and a BXPA1 to generate a loconet message concerning block occupancy? Thank you………Greg J

    Greg: The occupied output should be showing up on LocoNet. However, if the optical output is not activating, it is not clear if there is a LocoNet message or not. The BXPA instructions are very poorly written and give no clue about how to check the occupied output or where it should be on LocoNet relative to the base address.

    I hate to say these words, but I think you are stuck with Digitrax support. The Digitrax circuitry is proprietary and we have no insight into how it works, and the manual does not address your question. If the output is not closing, then it is a BXPA1 problem not a Jack interface problem.

    If you are stuck, we do have the PSXX-AR, our new version of the PSX-AR. It has the same block detection as the now discontinued PSX-AR except with the added ability to automatically calibrate the trip current for the block. You already know this works for your system with the Jack AD Sensor [Discrete]. It does not directly have a normal/reverse output for LocoNet. However, with a dual channel optical coupler on J11 (e.g. part number LTV827, no other circuitry required) you could interface the PSXX-AR to LocoNet via the Jack Discrete and have normal or reverse status. The PSXX-AR also allows you to set the polarity if you want, not just monitor it.