The position or speed of rotation of a stepper motor may be controlled by energising the windings in a sequence. Power output can be controlled by using a set of outputs, one per winding, using MOSFETs connected to the digital microcontroller outputs. The electronics are similar to that used for control of an LED using PWM, but the software control loop is different activating a group of outputs in a predefined sequence.
By using two stepper motors it is possible to have controlled movement in both X and Y directions. Similarly, stepper motors may be used to select and rotate Gobos, select and rotate prisms, adjust zoom and focus, and to insert coloured filters in the beam of intelligent fixtures.
The fixture below is one of the simplest - with 8 colours and a LED lamp. It uses a block of 8 DMX channels for control.
|
A |
Pan |
|
A+1 |
Tilt |
|
A+2 |
Colour |
|
A+3 |
Gobo |
|
A+4 |
Shutter |
|
A+5 |
Dimmer |
|
A+6 |
Movement |
Base address and offsets for the XMove moving light fixture.
See also:
Prof. Gorry Fairhurst, School of Engineering, University of Aberdeen, Scotland.