System 1 antenna control system update April 13, 2020

By Glenn Davis

I thought I would put out a System 1 status, so you can see what we’ve been working on the past couple of months.  To quickly summarize:  Lewis Putnam has been concentrating on the System 1 hardware design (Please see the hardware diagram below) to support automatic tracking of the Haswell Mount.  Additionally he has been looking at the individual mount axis characteristics to see how well they can support sidereal tracking (See detail text below). 

Phil Gage has supported myself looking at an Elevation axis movement issue we had seen at the site.  We found a loose cable on our March 1 trip which appeared to be causing the elevation axis issues.  Additionally, Phil has been working on the hardware/software interface for the Labjack hardware (Please see the hardware diagram below).  The Labjack hardware, the U3 and JTick-DAC components, will be used to control the mount axis rates.

I have been updating the System 1 Hardware Simulator to support the Numato Relay Board and Labjack U3/JTick-DAC hardware devices.  Additionally, I’ve been working on the hardware/software interface to the Numato Relay board.  This device will be used to enable the drive controllers and control the direction of the Elevation Axis.  Using the work completed by Phil and the Simulator modifications, I’ve been able to test and debug most of the automatic tracking software modifications and simulate the System 1 tracking celestial objects over large periods of time (hours).    

Here is a more detail summary of the past work and future work on the System 1 team (Before site modifications are performed, we will present our design work to the DSES Engineering Team):

March 12 2020 Trip

  • Purpose: Determine relationship between Az / El drive command voltages and rate resulting from command voltages
  • Approach:
    • Made measurements to calibrate mount Az and El drives (Rate as function of applied voltage)
    • Took measurements separately for Azimuth and Elevation
    • Measured both CW and CCW rates for Az and Up/Down rates for Elevation 
    • Varied voltage via Trailer Control Panel Az and El rate potentiometers from 0 to 5 volts (.2-volt increments for voltages below a volt and 1-volt increments from 1 volt to 5 volts.)
    • Logged axis position data in System 1 software
    • Captured measurements in Excel spreadsheet and plotted
  • Findings:
    • Plotted results indicate linear relationship between voltage and rate for both positive and negative rates for both axes.
    • Performed linear fit to determine slope and intercept values that can be used to convert an axis rate into a command voltage.
    • Unique Slope and intercept parameters will be used in System 1 software
    • Slowest drive rates are .02 deg/sec for Az and .06 deg/sec for Elevation; lowest rates were consistent between positive and negative rates
      • Rates needed for sidereal track are about an order of magnitude lower
      • Will have to cycle axis drives on / off to achieve sidereal track rates
    • Elevation Potentiometer voltage will not go to zero
      • Lowest voltage is somewhat less than .2 volts
      • Cause is unknown but potentiometer is most likely candidate
    • Measurements for Elevation similar to results from August 2019 but measurements for Az significantly different from August results, unknown cause
    • Measurements in March were more extensive and disciplined. Will use calibration from these measurements in the implementation of the software.

System 1 Mount Drive Interface Hardware Design/Implementation

  • Progress:
    • Completed hardware circuit design
      • Interfaces to the tower drive electronics via the Jones Plug
      • Uses a Labjack U3 device / TickDAC that provides two +-10-volt Digital Analog Convertors to enable setting Az / El axes control voltages
        • Labjack has necessary digital I/O to interface to the axes encoders so downstream can be used to replace the now obsolete Integrity Systems digital I/O board
      • Uses Numato 8 Relay Board to enable the drive controllers and control direction in the Elevation Axis
    • Developed an approach to integrating circuit into the trailer rack
      • Mount components on a small rack shelf about 6” deep
      • Mount shelf on back rails of the Trailer Rack
      • Move Jones cable from Manual control panel to System 1 Drive Control when using System 1 for drive control
    • Acquired major components and some minor components – Numato 8 Relay Board, Labjack interface device, Jones plug and wire
  • Next Steps:
    • Colorado Springs
      • Acquire remaining additional components – Switch, LEDs, resistors, rack shelf/panel
      • Mount components on rack shelf and wire components together
      • Integrate / test software with drive control assembly
    • Site
      • Install rack shelf / panel
      • Install updated software
      • Test / debug automated drive control

Please pass this on to other individuals who may be interested.

Thank you.
Glenn Davis