Program tips > How to Set Servo Travel Limits

by Mike Shellim

Unlike ATV on most other sets, the travel limits you set on the Evo are true electronic end stops. If you have a combination of stick movements which would cause the servo to exceed the limit, the servo simply stops dead at the values you set. There is however an undocumented trick in setting them up.

First lets look at an example to see why it's useful.

Vtail example

On an aerobatic V-tailer, you usually want large rudder movement (for stall turns), as well as large movement for elevator control. Suppose that each servo has a potential movement of +/- 100 units, and but the linkages would get damaged at any movement above 85 units.

In order to prevent damage to the linkages, on most sets you would have to split the available 85 unit travel between the two rudder and elevator, e.g. 50/35. If you increased the rudder movement, you'd have to decrease the elevator or risk damaging the linkages. Alternatively you could set rudder and elevator for +/- 85 unit movement, but you'd risk damaging the linkages if you push the stick into the corner.

With the Evo, you need not compromise. You could set elevator and rudder controls to whatever you like. Then simply set the LIMIT value on each servo to +/-85. If you applied maximum rudder and elevator together, each servos would stop dead when it reached 85, before it could do any damage.

Setting Limits

Here's the correct way to set up servo travel limts. Like the servo center tip, it uses the button to over-ride current stick position and trim settings while making the adjustment. Again, this is not properly documented in the manual.

  1. Go to the Servo Calibrate screen.
  2. Select the first point (P1)
  3. Press the digi-adjuster to edit.
  4. Press the key.
    The servo - and vertical bar - will then jump to the left hand end-point. You can now fine tune the servo position.
  5. When finished, press the button again to release. The servo will move back to reflect the current stick, trim and mixer settings.
  6. Repeat for the other end point (P5)