Last year, I was having problems with some of the track occupancy block sensors on the mainline automation. Turns out that the new UP Walthers engines use a lot less power than the previous engines, and the NCE BD20 were having difficulties detecting the presence of the trains.

Instead, I finally finished replacing the problematic sensors by newer Iowa Scaled CKT-BD1 sensors:

Only blocks B320, B321, B340 + B350, and B370 have the new sensors.

This is located behind the Mountain 1 Block Panel. Quite frankly, it’s a bit of a mess and that install needs an organization overhaul at some point:

Whereas the BD20 sensors were adjusted by an (optional) variable resistors, the newer Iowa Scaled CKT-BD1 are all electronic and embed a smaller ATiny85 controller.

To adjust their sensitivity, the procedure is fairly simple and follows the CKT-BD1 user manual:

• The track needs to be powered, so we want the command station turned on.
• Make sure the track is not occupied -- e.g. turn the automation’s toggle switch off, and visually assert there are not trains, either engine or cars sitting on the track.
• Locate the little push button on the BD1 sensor card for the block to be calibrated.
• There may be a red occupancy LED on -- this indicates the sensor is detecting track occupancy, and if the track is visually empty that means there’s too much current leakage. So that’s why we need the calibration.
• Press and hold the button.
• There’s an orange LED that should start blinking slowly. Keep holding.
• Once the orange LED stays solid, release the button.
• The orange LED should start blinking rapidly 3 times.
• After that, the success depends on the red occupancy LED:
• If the red occupancy LED should go off, the calibration is successful.
• If the red occupancy LED stays on, there’s a problem due to too much current leakage, and at that point we should start worrying and start thinking about reassessing our life goals or something.