ip-focuser

ip-focuser is an arduino based focuser for an astronomical telescope. Communication is via an HTTP json API. Also included in this project is an Indi driver to allow it to be used with any Indi client. Feaatures include backlash compensation and an always approach counter-clockwise motion strategy to reduce the effects of mirror-shift with SCT telescopes. When used with the Ekos Indi client, reliable auto focus can be achieved, limited only by local seeing conditions. for more information on Ekos and Indi see here http://indilib.org/about/ekos/focus-module.html.

Currently the system is providing automatic focus for Ballyhoura Observatory

Device Hardware

The focuser hardware is based on the following parts

1. 1 x Arduino nano (http://www.dx.com/p/arduino-nano-v3-0-81877#.ViKE2RCrRE4)
2. 1 x PCB ENC28J60 Ethernet Module HanRun HR911105A (14/10) (http://www.dx.com/p/pcb-arduino-enc28j60-ethernet-module-blue-140971#.ViKE_xCrRE4)
3. 1 x TB6560 3A Single-Axis Controller Stepper Motor Driver(http://www.dx.com/p/tb6560-3a-single-axis-controller-stepper-motor-driver-board-green-black-red-217142#.ViKE8hCrRE4)
4. 1 x Old uniplar stepper motor that I found in the shed.

See the source documentation of the arduino firmware for wiring details.

Device HTTP API

Getting state

Task	Method	Path
Get the state of the focuser	GET	http://192.168.1.203/focuser

Response Code 200

Response body

{
    "uptime": "00:01:23",
    "speed": 112,
    "temperature": null,
    "temperatureCompensationOn": false,
    "backlashSteps": 200,
    "absolutePosition": 10000,
    "maxPosition": 20000,
    "minPosition": 0,
    "gearBoxMultiplier": 10
}

Motion

Task	Method	Path
Move the focuser to an absolute position	GET	http://192.168.1.203/focuser?absolutePosition=8000

NOTE: This call will block until motor motion completes.

Response code 200

Response body

{
    "uptime": "00:01:46",
    "speed": 112,
    "temperature": null,
    "temperatureCompensationOn": false,
    "backlashSteps": 200,
    "absolutePosition": 8000,
    "maxPosition": 20000,
    "minPosition": 0,
    "gearBoxMultiplier": 10
}

Configuring speed and backlash

Task	Method	Path
Configure stepper speed	GET	http://192.168.1.203/focuser?speed=250

This call will result in no motor motion. It will set the speed for future motion requests.

Response code 200

Response body

{
    "uptime": "00:01:52",
    "speed": 250,
    "temperature": null,
    "temperatureCompensationOn": false,
    "backlashSteps": 200,
    "absolutePosition": 8000,
    "maxPosition": 20000,
    "minPosition": 0,
    "gearBoxMultiplier": 10
}