MX2 Motion Control

Motion Control

Camera and Intervalometer

All camera settings can be viewed and modified by selecting the 'Camera' option in the main menu.  The following options are available: 

 

Interval

Sets the interval between shots, in seconds.  The camera will fire on the interval, or as soon as possible afterwards if another event was blocking the camera from firing.  For example: if you set a post exposure delay of 1.5 seconds, and an interval of 1 second, then your camera would not fire more often than once every 1.5 seconds because the post exposure delay blocks the camera from firing.   This setting may be modified directly on the main screen.

This value is automatically saved to permanent memory and will persist between power cycles.
 

Max Shots

Sets the maximum number of exposures to take in a shoot.  Once this number of exposures has been taken, the shoot will automatically turn off - disabling the camera and the motors.  Note that if you save a value lower than the current shot count while running, the shoot will immediately turn off.

This value is automatically saved to permanent memory and will persist between power cycles.

 

Exp. Time

Set the amount of time, in milliseconds, to trigger the camera exposure.  This can be used for bulb-mode shooting.

This value is automatically saved to permanent memory and will persist between power cycles.

 

Exp. Delay

Sets the post-exposure delay time, in milliseconds.  Triggers a delay event immediately after the exposure completes that prevents any other events from occuring for the defined period of time.  Especially useful when having the camera controlling the exposure and operating in Interleaved mode to keep the motors from moving while the camera is exposing.

This value is automatically saved to permanent memory and will persist between power cycles.

 

Focus Tap

Sets the amount of time, in milliseconds, to trigger the focus line for the camera before triggering the exposure.  This can be used to wake up a sleeping camera, or call autofocus when needed.

This value is automatically saved to permanent memory and will persist between power cycles.

 

Shutter+Focus

Enables the focus line being brought high in conjunction with the shutter. Some cameras, especially Nikon cameras require both lines triggered to take a picture.

This value is automatically saved to permanent memory and will persist between power cycles.

Motor Axes

Each motor under control is considered an axis of motion.  They are generally considered to be at rest when the intervalometer is off and in motion when the intervalometer is on. 

The direction and speed of a given motor are set on the Main screen, or when moving the motor manually. 

Please note that in an open-loop system, where there is no feedback from the motor to the engine, it is very difficult to achieve highly accurate moves.  All distances/speeds entered will be approximate in practice without a feedback mechanism.  It is possible to run up to two pulse-based encoders to allow you to accurately measure the speed and distance of each movement, but the firmware does not yet support it.

Configuring Axes

To configure the settings for a given motor axis, from the Main menu select either the 'Axis 1' or 'Axis 2' menu option.  The following settings are available:

 

Ramp Shots

Configures a linear ramp of motor speed.  This allows you to "feather in" to a move by slowing gaining speed across several frames of the output video.  For example, entering a value of '10' will cause the motor to start at a speed of zero, and reach you configured speed after ten shots. 

If you have configured a Max Shots setting for the camera, the Engine will automatically ramp down the motors speed as your shoot nears the configured Max Shots.

This value is automatically saved to permanent memory and will persist between power cycles.

Note: when Ramp Shots is set to a value other than zero, the speed display for the motor goes to zero when the shoot is started, and will increase after each shot until the previously configured speed is reached.  If you stop the shoot before the previously configured speed is met, the motor will stay set to the speed it had ramped to, and you will have to increase the configured speed back to the desired level.

 

RPM

Configure the maximum RPM available for the current motor. You may select fractions down to 1/100th RPM.  It is important that you enter the crrect value for your motor, otherwise speed displays will be incorrect.

This value is automatically saved to permanent memory and will persist between power cycles.

 

Fixed SMS

Causes shoot-move-shoot (interleave) mode to move a fixed distance between exposures, rather than calculating distance based on Inches Per Minute configured and current interval.  When fixed SMS is enabled, the Slow Mode IPM is ignored, and all motion is in interleaved mode. See Motion Modes below for more information.

This value is automatically saved to permanent memory and will persist between power cycles.

 

Angle

Set the nearest angle for this axis.  The angle setting is used to apply calibration for certain angles of track, such that the motor performance is automatically adjusted to handle the effects of the additional load caused by gravity at different angles.  The possible values correspond to the calibration values available: 0', 45', and 90'.  This value is only applicable to linear axes.  For more information, see Calibrating Motor Performance below.

This value is automatically saved to permanent memory and will persist between power cycles.

 

Calibrate

Calibrates motor performance for a given load and angle of track (for linear axes).  See Calibrating Motor Performance below.

All calibration values are automatically saved to permanent memory and will persist between power cycles.

 

Slow Mode IPM

This is the speed floor for continuous motion. It determines when the configured slow motion mode will kick in.  See Motion Modes below for more information.

This value is automatically saved to permanent memory and will persist between power cycles.

 

Dist. per Rev.

Configure the distance traveled per revolution for the given motor axis, in inches.  This is how far the axis will travel with one complete revolution of the motor.  It is tied directly to RPM to determine actual distance-based speed inputs (i.e. IPM). 

To calculate distance traveled per revolution, you will need to know about the output of your gear chain and what the final travel distance will be.  For example, to calculate the total distance traveled for a single-stage pulley drive train, you would multiply the Pitch Diameter of the pulley by pi.  In this way, the total distance travelled would be the effective circumference of the pulley.

This value is automatically saved to permanent memory and will persist between power cycles.

 

Min Pulse

This option is used to broadly tune the motor's performance under load in the 'Pulsing' slow motion mode.  With no feedback (encoders, etc.), motor axes will display varying behaviors at different speed levels with different loads.  This value should only be modified when the motor is incapable of moving load at the lowest speed settings in the Pulsing motion mode.  When the motor does not move at all at a very low speed in Pulsing mode, adjust this value higher.

This value is automatically saved to permanent memory and will persist between power cycles.

 

Motion Modes

The motion mode is automatically determined based on the currently set speed of the motor and the defined speed floor for continuous motion.  Once you set a speed lower than the floor, the motor will switch into the chosen "slow" mode. The following "slow" modes are available:

Pulse

In Pulse mode, the motor is run at full speed in the configured direction for fractions of a second - but much longer than a normal pwm period.  This allows the motor to have more torque, but still cover very short distances over time.  While the speed of the motor is maximized when it is moving, the overall measured speed will be much lower. 

While this mode can achieve much lower speeds, it generates more vibration in the motors.  For this reason it is to be avoided when using long lenses or doing critical focus work.

 

Interleave

Interleaving motion between shots is often referred to as "Move-Shoot-Move."  In this mode of control, the motors are not moving while the camera is exposing.  Once an exposure has completed, the motors will move a set distance, and stop to allow the camera to fire again. The distance traveled between shots is based on the inch-per-minute travel rate currently configured and the current shot interval.  (Even if configured in percentage of speed, it is converted to a distance for this calculation.)  The calculation is defined as: IPM / (60 / interval). Or, more easily understood: if in interleave mode, the distance traveled between shots is the inch-per-minute distance divided by the number of shots per minute.  So, with a 1 second interval and a 1 IPM speed setting, the moor would move the 1/60th of an inch between each shot.

Fixed Interleave

Fixed interleaving is turned on by enabling the "Fixed SMS" setting for an axis, and may be controlled for individual axes in their respective settings menu.  When Fixed SMS is enabled for a particular axis, the input for speed on the main screen will convert to hundredths of inches, and allow you to specify exactly how many fractions of an inch (from 0.01" to the maximum travel in one minute) to move between shots.  This mode only works if the global motor slow motion mode is set to "Interleave".

This mode is particularly useful for very slow movement, as it ties the motors movement to the shot interval, and can also be used with long lenses and critical focus work as the camera is not moving while exposing.  However, for some cases it may be less desired as it will increase sharpness and there will be no motion blur in stationary objects.

 

Setting the Motion Mode

The motion mode can be configured in the Settings menu, by selecting the 'Motor Sl.Mod' option.  This parameter is global for all motors and may not be set independantly.