Tag Archives: JMRI

JMRI sensors and turnouts

I’m still a novice when it comes to JMRI. It is a really powerful bit of software but lacks a bit when it comes to documentation. This is especially so in the area of scripting. Still… more of that later.
A simple way of regarding the inputs and outputs that JMRI uses is to regard all inputs as sensors and all outputs as turnouts (points). It’s a simple terminology but easy to get ones head round.
On Key Hernan most of the inputs are TOTI sensors that report whether a section of track is occupied or not. It does this by sensing traction current is being taken by a section of track. This is usually because a locomotive is in the section. Other sensors could be press buttons or switches on a control panel. The turnouts can be actual turnout mechanisms (servos or solenoids) or signals, level crossing gates etc.; in fact almost anything that needs to be physically moved.

Power up!

Today I managed to get all the power feeds installed via the TOTI units along with the servos for the point controls.
To install the servos I used the FCU to set the servo to the mid position, jammed the point switch blades to the mid position then screwed the servo mount down. It was then fairly easy to set the servo movement limits using the FCU again. The fiddly bit was setting the position of the microswitches on the servo mounts. The microswitches are used to control the polarity of the switch blades as the point changes position. It’s worth the trouble of fitting them as it helps to prevent electrical continuity problems if the swtich blades don’t make good contact with the stock rails.
The TOTIs worked perfectly and were feeding back track occupancy information to the JMRI control system.
It all seems to be working OK and a test run went OK.

A more complex script

I have written a more complex script that uses track circuit sensors to detect the locomotive position and then operates points and loco speed and direction. Sound effects are also controlled by the script. This video show the script running. In the video you will see the JMRI Sensor table status, the dynamic track diagram and the output of the script.

You will be able to see the contents of the smaller windows if you play this video in full screen mode.