Examples : Controlling a servo using S01 - S12

Mike Shellim   4 January 2002

This article shows a method of controlling a servo directly from an S01 - S12 switch, without using up any of the A-M controls.


The method uses the FIXED VAL control. This is a virtual control, i.e. it is does not appear in the Assign Controls screen.

Simple 2-position switched output 
                     |             |
FIXED VAL (S01*) --> |   ------>   |--> servo
                     |             |
  1. In the Assign Servo, assign the servo to FIXED VAL (appears after AUX 4 in the control menu). 
  2. Go to the the Servo Travel screen and select the servo 
  3. Adjust the curve. The "curve" is actually a horizontal line representing the fixed value. Set it to the required end-point.
  4. Assign switch S01 - S12 (instead of "ON").
  5. Go to the Servo Centre screen and select the  servo.
  6. Set the other end point by adjusting the servo centre.

This method will only provide travel from centre to one end point. To obtain full travel, use a servomix to mix two opposite FIXED VAL's as follows:

Better Version (full travel)
                    |             |
FIXED VAL (S01*)--> |   ServoMix  |--> servo
FIXED VAL (SO1) --> |             |
                    |             |

S01 flips between the two inputs, by making one input active and the other inactive. If one input is +100 and the other -100, the mixer outputs (0+100)=100 or (-100+0) = -100. Therefore  depending on the switch position, the mixer outputs -100/+100 i.e. full travel.

Servomix set up

Input Control/Mixer Switch  Curve        Remarks
1 FIXED VAL S01* +100 Switch flips between inputs. Make sure only one input is active (*) at any time.
2 FIXED VAL S01 -100
  1. In the Assign Servo screen, assign a Servomix.
  2. In the Assign Mixers screen, goto the servomix and assign two FIXED VAL inputs.
  3. Goto to the Servo Travel screen
  4. Choose the first FIXED VAL input 
  5. Assign any switch S01 - S12, and make it active (*)
  6. Set the travel for the first end point.
  7. Repeat 4-6 for the second input. In step (5), make the switch inactive (no *).

Note any switch S02 - S12 could be substituted for S01.