Safety switch

Mike Shellim 4 Dec 2013
Last updated 22 April 2016

Here's a recipe for a 'virtual' safety switch. It requires two hands to activate, making it suitable for safety-critical functions such as calibration mode. (A modified version is used as a motor arm/kill switch).

To switch on:

1. Apply full up elevator and full left aileron, and hold.
2. Pull and release momentary switch SH.
3. Release stick(s).

To switch off:

• Pull and release SH.

There is no need for a switch check at startup, since the switch defaults to off.

How it works

The basic safety switch is implemented using four logical switches:

• L1 and L2 define the stick gesture to set the latch:
  (aileron left AND ele back AND SH-down)
• L3 is the latch. L1 sets, L4 resets.
• L4 is the gesture to reset the latch (SH-down). '!L1' means 'not L1', i.e. "not while setting the latch", and is necessary to prevent a set/reset oscillation as SH is used both for setting and resetting.

Integrating in your setup

Use L3 as the switch for whatever you want to control. If you wish to use different logical switches to those shown (e.g. if L1-L4 are already used), make sure to amend all references as necessary.