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.
On Autoscope box, there two four pin connectors at the top that get power (+24VDC and ground) and signal and ground for dome rotation power and direction.
There is a 9 pin connector that gets signal and ground for shutter power and direction. The relays for these in the Autoscope box get power from the two four pin connectors.
Finally there is a 4 pin connector that gets +24VDC and ground from the watchdog. If there is no voltage, then the dome closes.
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. DC +5 and ground are connected to RPi power, A and B outputs are connected to level shifter input channels; level shifter output channels are connected to RPi GPIO pins.
| Encoder pin | function | wire color | D connector pin | D connector color | connect | level shifter wire color |
| 1 | +5VDC | red | 2 | red | RPi +5V | |
| 2 | gnd | org | 8 | wht | RPi Gnd | |
| 3 | Bbar | brn | 3 | org | ||
| 4 | B | blk | 7 | vio | level B2 | grn |
| 5 | Zbar | grn | 5 | grn | ||
| 6 | Z | vio | 9 | wht(outer) | ||
| 7 | Abar | blu | 1 | brn | ||
| 8 | A | yel | 6 | blu | level B1 | blu |
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.S
| Sensor wire | function | circular connector pin | color | level shifter | color |
| 1 | wht | ||||
| red | gnd | 2 | blk | RPi gnd | |
| blk | signal | 3 | brn | level B3 | gry |
| grn | +DC | 4 | red | RPi +5V |
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