© Sierra Radio Systems
This project uses the standard General Purpose IO board (GPIO), HamStack CPU board and a custom designed control head. The control head connects to the control board using standard CAT5 8 conductor cable. The cable provides power and ground plus data between the two devices. As buttons are pressed on the control head, the commands are sent to the GPIO board, relays actuated, then the GPIO board sends a confirming packet back to control head and turns on or off the appropriate control head LEDs or LCD text.
Front view of the control head. Each of the 12 buttons can be set to light up either red, yellow or green or turn off. The LCD is a 2 line x 16 character backlit display. The lower right is an optical encoder.
Side views of the control head allows you to see the two boards. The top board hosts the user interface buttons, LCD, etc. The bottom board contains a local PIC CPU chip, serial interface connectors, etc.
The boards communicate using RS485 electrical signaling. This allows multiple devices to be connected at the same time to he control network. The GPIO board has two RJ45 connectors hooked in parallel. This allows us to daisy-
What would it take to build one of these?
The control head is mounted in a TenTec chassis box. The front panel was designed with Front Panel Express. In this application, the two rows of buttons on the left side are used to select one of 8 antennas. When antennas are selected the LCD is updated and the LED on the selected band button lights up green.
The buttons in the upper right corner control another set of relays on another GPIO board controlling other coax relays.
The buttons used on the control head are high quality buttons used in video switching equipment. Each button can be illuminated by a red or green LED.
The GPIO board has 8 SPDT relays which can be used to control just about anything. In this application, the relays switch coaxial antenna relays. One big advantage of the GPIO / control head design is the use of the RS485 serial interface. This interface allows you to locate the relay board far from the control head, up to thousands of feet.
You can also put multiple devices on the same serial network. This means that each board is programmed with a unique address so when the control head sends a command to turn on a relay, the command is only decoded by the board that is being addressed.
The control head was designed for multiple applications. The knob in the lower right corner is connected to a digital optical rotary encoder. While it is not used in the antenna controller yet, it will eventually provide menu selection and other control functions.