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About the Model Railroad

RTAC Software


The Randall Museum in San Francisco hosts a large HO-scale model model railroad. Created by the Golden Gate Model Railroad Club starting in 1961, the layout was donated to the Museum in 2015. Since then I have started automatizing trains running on the layout. I am also the model railroad maintainer. This blog describes various updates on the Randall project and I maintain a separate blog for all my electronics not directly related to Randall.

2018-09-22 - Automation Motion Sensor

Category Randall

I’ve installed the motion sensor with the AIU:

  • Modified the AIU to have 4 terminal outputs.
  • The 2N2222 is stuck between terminal pin 14 and one of the outputs (ground).
  • The 3 remaining terminal output match the motion sensor pins: ground, signal, 5V.

More technical details can be found on this blog post.

I removed the sensor used on the tablet -- it had become inoperative a second time in a row. I think the tablet software lost the USB connection, as unplugging and replugging the USB cable was enough to make it work.

New sensor is AIU #50 bit 14. Changed the automation script so that this pin activates PA-Run3 (the sensor button) as well as the RTAC-Motion variable. It also sends a GA stats event.

I originally had plans to put up to 5 PIR sensors. Turns out that one covers enough of the area, and I even had to reduce the sensitivity -- once people move to the level of the trains, the system activates. When using the max sensitivity, it could detect almost up to the door, which makes it activate too often and too soon.

Now that the initial test works great, I will probably 3D print a small enclosure for the sensor to limit dust.

Trigger stats look great, as can be seen on this sensor trigger-per-hour graph (which does not relate to train runs):

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