SigOS: Hardware

The Signal Operating System is designed to operate on low-cost hardware. This encourages extensive use for Signals and Detectors throughout most railroads, large and small.

Components

CdS photoresistor

Closeup of CdS (cadmium sulphide) photoresistor.

A CdS photoresistor is a light-sensitive resistor. It is used to detect the ambient light at the signal head, which is used by SigOS to control the brightness of the WS281 LEDs.

• Pin 1
  • Either wire from CdS photoresistor
  • Wire color: Green
  • Function: Control voltage into GPIO P1 of Control Board A/D converter
• Pin 2
  • Other wire from CdS photoresistor
  • Wire color: Yellow
  • Function: +3.3 volt power