Tutorials : Combi-switch with Auto Attenuation

John McNamara   3rd Jan 2002

This application demostrates (a) analogue switches and (b) a clever use of the "mixer priority" feature to enable/disable a mixer input via a switch - MS.

Implementing Combi Switch with Auto Attenuation

Using a combi-switch may be considered by some to be that lazy mans way, but when flying as well as negotiating a cross-country course it is a real boon. If you are flying a scale glider it is even more useful. But as soon as you meet a thermal you need to switch out the combi-switch since, as per full size, you need to fly the circle with crossed controls. Using the comi-switch in these circumstances, you could find yourself needing inside rudder to maintain speed in the circle but opposite aileron to prevent the model rolling inwards. This is caused by the yaw-roll couple that most gliders have, but especially noticeable on scale machines. At full control movement with the controls crossed and combi-switch on, the rudder would be round about neutral! It was necessary to switch off the combi-switch before thermalling. My problem was that I would forget until I realised that my flying was even more ragged than normal. I was sure that the P4000 could offer a software solution, and here it is.

We do not use the Combi-switch as such but rather use a multimix on rudder with aileron as one input. However, this input is switched by a V-Analogue switch, which is assigned to rudder control.

Nominally the combi is on, but as you apply rudder input the combi is gradually turned off.

Setting Up

Menu/Screen Task
Assign Controls K = Aux
A = Rudder
C = Aileron
Assign Servos - rudder Servomix
Assign Mixers - rudder

Input 1 rudder+trim
Input 2 Aux-*
Input 3 Aileron
Priority = ON (enables Aux to switch off Input 3)

Assign switches - A*

From Control A
Effect min =0%
Effect max = 100%
Window = TO 100%,  FRM 0%
Hit R to change "A" to "V".

Servo-travel/curve - Rudder servo

Input 1 rudder = On
Input 2 Aux = On or Switch* (with a switch you can turn the combi on or off completely as you wish)
Input 3 Aileron =V* -A* (nominally on with control A in centre position)

NB: in input 2 above the Aux input should have all servo points set to 0%, Whilst inputs 1 & 3 must have servo points travelling the same way.

[Editor's note: Instead of K/Aux for input #2, you could use FIXED VAL with value zero - this would save using up a control. Remember the ordering of mixer inputs is important when using Priority=ON - see the User Manual for more info]


NB: With a switch (hardware or software) on input 2 - Aux*, you can turn the macro on or off.

In practice this is wonderfully intuitive. More rudder input is needed than without the mix being in, but when flying you simply move the stick enough without thinking about it. Try it, you'll like it!

Copyright © J. McNamara   2002