This is an old revision of the document!
Dome control
Dome control is implemented through software running on a Raspberry Pi. Initial implementation controls dome motors through the Autoscope box with Opto 22 relays, but goal would be to just control the dome relays directly. The Raspberry Pi has a RELAYPlates card with 7 relays, which control shutter direction, shutter power, dome direction, dome power, and watchdog reset. These relays connect the control lines to ground.
The dome encoder gets +5V and ground from the RPi, and receives 5VDC signals from the A and B phases of the quadrature encoder. These are wired into RPi GPIO ports through a level converter that converts 5V to 3.3V.
The home sensor gets +5VDC and ground from the RPi, and receives a signal on a GPIO port that is normally low, but goes high when the home magnet is in proximity to the sensor.
Low-level functions are implemented in the APOAshDome.py module. An ASCOM Alpaca interface was implemented using the templates from the AlpycaDevice package.
Software is archived at https://github.com/holtzmanjon/APOAshDome