MX2000 System for the 41-inch Telescope

Last Updated on 1-12-2004

Wiring Notes

Only 4 of the 6 motor wires are needed for the new MX2000 system. The red a green wires should not be connected to anything or each other. The label on the MX2000 case for outputs 1,2,3 and 4 should be wired up to black, orange, green and blue respectively.

Notes on the old Superior Electric Motor Driver Electronics

Maximum Speed = 2520 steps per second
Acceleration = 500 steps per second²
Set Rate (Medium Speed) = 1000
Track rate in pulses per second = 103(for tracking), 102 (for moves)
Guide Rate = 40
Motor Specifications

MX2000 Programming Notes

The program provided by Superior is good for testing but will not satisfy our telescope requirements.
I have written a short Visual Basic program for testing. It's stored in a folder called "MX2000Tester". It has a terminal window and buttons for manual testing of motor commands.
The communications port settings are as follows: COM1, 9600 baud, No parity, 8 data and 1 stop bit.
The commands that seem relavant are MOVE, JOG, SPEED, ACCEL, DECEL, MAXSPD, ABSPOS. Here are some examples.
- MOVE(1)=-1 ' Move motor #1 one unit (e.g. CCW)
- JOG=0,1 ' Ramps motor #2 to maximum speed (eg. CW)
- MAXSPD=1, 1 ' Sets the maximum speed of both motors to 1 unit/second
- ACCEL=1.86 ' Maximum acceleration (The minimum acceleration setting for MX2000 seems to be ~1.86 units/second² (See required SS2000D12 settings below))
- DECEL=1.86 ' Maximum decleration
- ABSPOS ' Returns the number of units moved from the start position. This may be good for error checking.
The MX2000 system seems to have it own unit of measure. For example speeds must be given in terms of units/seconds when programming.
SFA Experimental Data:
- The setting on the SS200D12 Motor Drives is set to 20000 steps per revolution.
- Experimentally this gives 10 units = 1 revolution. For example, "MOVE=10" rotates motor A one revolution.
- The information printed on the motor says 200 steps per revolution so I suppose we are "microstepping".
- "SPEED=1" followed by "MOVE=10" causes Motor A to move 1 revolution in 10 seconds.
  - Note: q=wt. So t=q/w=10 seconds.
- "SPEED=50","MAXSPD=50", "ACCEL=10", "DECEL=10" followed by "MOVE=250" causes Motor A to move 1 revolution in 10 seconds.
  - Note: q=¹/₂at², w=at, and w²=2aq for acceleration from rest to the maximum speed.
  - So q=w²/(2a)=125 units and t=w/a=5 seconds units for ramping up all the way to MAXSPD (w_max) from rest. The total time for ramping up and then back down would be 10 seconds (q_a=2w_max²/(2a)=250 units).
Calculating Move Times:
- Now consider the case where the move distance q_total is less than q_a=w_max²/a.
  - Here MAXSPD (w_max) is not reached. The total number of units moved is then q_total=2(¹/₂a(t/2)²).
  - So MOVETIME = t = 2(q_total/a)^(-1/2) for q_total<q_a.
- Now consider the case where the move distance q_total is greater than q_a=w_max²/a.
  - Here MAXSPD (w_max) is reached and maintained for some time t₂=q₂/w_max where q₂ is the distance moved during the time when the motor is moving at its maximum speed.
  - The time for an accleration is t₁=w_max/a and the distance moved during an accleration is q₁=w_max²/(2a).
  - Note that MOVETIME = t = 2t₁ + t₂ and the distance moved is q_total = 2q₁ + q₂.
  - So MOVETIME = t = q_total/w_max + w_max/a for q_total>q_a.

Dan Bruton