HW Segment actuator
Segment Actuator expanders are designed to stop a train on the corresponding segment. The concept behind this expander based on the Lenz Asymmetrical DCC and ABC functionality of train-decoders. The following descriptions are based on link::https://tonystrains.com/lenz-asymmetrical-dcc-and-abc/[this] article.
ABC (Automatic Brake Control) works in conjunction with Asymmetrical DCC. Asymmetrical DCC is a way to trigger ABC in the decoder. This gives the ability to stop trains at a section of the track with Asymmetrical DCC.
The Asymmetrical DCC signal is generated by offsetting one phase of the DCC signal. This signal then triggers the Automatic Brake Control in the decoder. This causes the engine to stop at the distance set up in the Constant Stopping Distance feature. We implemented this using five diodes connected in the form as shown in the figure below.
The Segment Actuators uses this setup and also gives an interface (with GPIOs) to enable or disable this feature. Every Segment Actuator expander has two slots (A or B) and can enable or disable two segments. Each segment can be enabled setting two GPIOs to HIGH level, one connected to the PRU and one connected to the application processor.
