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192 General notes on freely programmable mixers

The previous pages have described a wealth of 
ready-to-use built-in coupling functions, in the context 
of the two menus »Wing mixers« and »Helicopter
mixers«. The fundamental signifi cance of mixers and 
the principle by which they work are described on 
page 159. The following section provides information 
about the so-called "free mixers". 
In addition to the pre-programmed mixers mentioned 
above, the 

mc-20

 HoTT also offers a number of 

freely programmable mixers in every model memory 
location, whose inputs, outputs and mixer ratios can 
be defi ned to meet one's own requirements. These 
include: 

8 linear mixers, numbered 1 through 8

•

4 curve mixers, numbered 9 through 12

•
These 12 mixers are certainly adequate for most 
applications and are certainly suffi cient when the 
potential of the pre-programmed coupling functions 
are utilized. In the »Mix active/phase« menu (see 
page 204), each of these 12 mixers can be activated 
or deactivated separately for each fl ight phase.
For the "free mixers", the signal present at any control 
function (1 to 16) can be assigned as the input signal
or,for a so-called "switch channel" (see further below), 
the signal from any switch can be utilized. The signal 
that is present at the control channel and passed 
to the mixer input is always infl uenced by its own 
transmitter control and by any control characteristic 
that may have been set, e. g. those specifi ed by 
the »Dual Rate / Expo«, »Channel 1 curve« and 
»Control adjust« menus. 
The mixer output acts on a control channel (1 
to  – depending on receiver type –  a maximum of 16) 
that can also be assigned freely. Before this channel 
routes the signal to the servo, it can only still be 
infl uenced by the »Servo adjustments« menu, i.e. 
by the the servo reverse, neutral point offset, servo 
travel and servo travel limit functions, and possibly by 
»Tx. output swap«.

One control function can be used for any number of 
mix inputs simultaneously: if, for example, several 
mixers are to be switched to act in parallel. 
Conversely, it is possible for any number of mixers to 
affect one and the same control channel. Particularly 
in the latter case, however, it is very important to 
ensure that the servo concerned does not strike its 
mechanical end-stops when several mixer signals 
accumulate excessively. For safety's sake, it may 
therefore be necessary to set an appropriate travel 
limit in the »Servo adjustments« menu.
For more complex applications, mixers can be switched 
in sequence. In this case, it is not the (transmitter) 
signal at the "output" of a control function which forms 
the input signal of the "series-wired" mixer, but the 
(mixed) signal "further back" at the "input" of a control 
channel. The following description of the free mixers 
includes several examples of this type.
In the software, one "free mixer" is always initially 
activated. Optionally the mixer can also be assigned to 
an ON/OFF switch. Since there are so many functions 
to which switches can be assigned, be careful to avoid 
(undesired) multiple assignments to a single switch.

… the 

•

mixer ratio, which defi nes the extent to 

which the input signal acts on the output of the 
control channel connected to the mixer output. 
The mixer ratio for linear mixers can be set as 
symmetrical or asymmetric. Curve mixers can also 
be confi gured with up to 8 points to suit one's own 
application and even implement extremely non-
linear curves.
…

•

the neutral point of a mixer, which is also 

referred to as the "offset". 
The offset is that specifi c point along the 
movement of a transmitter control (joystick, 
proportional control or switch) at which the 
mixer no longer infl uences the control channel 

connected to its output. Normally, the neutral 
point is the center point of the transmitter control. 
However, the offset can also be set at any other 
point along the control travel. Since there are no 
restrictions on the design of the curve mixers, 
setting a mixer neutral point only makes sense for 
the 8 linear mixers.

Occasionally, however, only a constant control signal 
is required at the mixer output, e.g. for a slightly 
increased "up-elevator" trim when the aero-tow 
release is closed – fully independently of its normal 
trim setting.
In this case a switch is assigned both to the aero-
tow release and the mixer; it is then used not only 
to open and close the release, but also to pass the 
desired trim signal to the elevator via the mixer ratio. 
To identify this special arrangement, this mixer input 
control function in the program is designated "S" for 
"Switch channel". 
In addition, if the corresponding "target channel" 
should now no longer be infl uenced by its "normal" 
transmitter control, isolate the latter from the function 
input of the affected control channel by way of the 
»MIX-only channel« menu (page 205). Here too, for 
clarifi cation of this there is an example of the function 
provided in the following menu description.