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Nov 24, 2016, 06:34 PM
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Taranis: Logical Switches, Part 1

Using Logic Symbols and Digital Electronic Schematic Diagrams as An Aid to Understanding and Designing Logical Switch Setups

I've found that it can be useful to draw schematic diagrams of equivalent digital electronic circuits for logical switch setups that I'm designing or analyzing.

For a fairly simple example, here's the code that activates and deactivates the CAL (Calibrate) mode in Mike Shellim's F3J/TD setups:

L3 is the output. When L3 is true the radio is in CAL mode (Flight Mode 1).

Here's what it looks like when translated into a schematic diagram:

To enter CAL mode the stick is held in the lower-left corner (L5 is true) and the spring-loaded SH switch is pulled (SH↓). To exit CAL mode, SH is pulled (SH↓) with the stick not in the lower-left corner.

An interesting fact about this arrangement is that the combination of L2 and L3 serve virtually the same function as a sticky. This is much easier to see in the schematic diagram than in the radio programming.

So why not use a sticky instead and save a logical switch?

Here's an alternate "circuit":

and here's the coding:

The changes are:
  1. L2 is not used.
  2. L3 is changed from OR to Sticky.
  3. L3-V1 remains set to L1, but L3-V2 is changed from L2 to SH↓.

An interesting but unimportant difference in the behavior of these two setups is that when the radio is in CAL mode with the alternate setup, pulling SH↓ will always exit that mode regardless of the right stick position. In Mike Shellim's setup, CAL mode cannot be released while the stick is being held in the lower-left corner, but will be released if, during the process of activation, the right stick is released before SH↓ is released. The reason for this difference is left as an exercise for the reader.

Last edited by Miami Mike; Nov 25, 2016 at 01:14 PM.
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