🚀 go-pugleaf

Chris Kaiser (kaiser@elec.canterbury.ac.nz) wrote:

    ... basic stuff about plane needing elevon type mixing deleted ...
 
: > As to mixing... it is probably possible.  The biggest difficulty
: > would be creating two "inverse" signals to drive the alternate
: > ailerons.  Once this is accomplished, then mixing the elevator
: > signal onto these signals is probably fairly simple.  To provide
: > fuel for thought... I'll repost something I wrote up a while back
: > on adding channels to a Tx.  The main relevance to this discussion
: > is basic control stick circuitry.
: 
:    ... good stuff on adding channels deleted ...
: 
: The way to do this in the Tx is to add the aileron and elevator
: channels together for one servo, and subtract them for the other
: - then use servo reversing if necessary to get the right actions.
: Building an "adder" and "sutracter" is not hard if you have some
: basic electronic knowledge. The subtractor is the trickier of the
: two as you need to set up a reference voltage equal to that of
: the control stick when it's at neutral. Somebody posted a Tx V-tail
: mixer quite a while ago that used this principle (same circuit, just
: different channels mixed). If that person is still on the net perhaps
: they could repost the circuit. Failing that, and if there is interest,
: I could post my circuit. However I must point out that I didn't get
: around to building it (not because I didn't think it would it work,
: but because I ended up using my computer radio for that model instead).

Well...... this sounds good on paper.  The problem is that the inside
of a Tx is a very hostile environment for electronic thing-ies.  Seems
that there is a great deal of EM garbage/noise being generated from
that long metal thing sticking out (:

Seriously, I tried a little op-amp adder for a dual rate circuit once
and it didn't work anything like I expected.  As I recall it worked on
the voltmeter *until* I reconnected the RF module and then it went nuts.
Seems that the op-amp tried to follow the RF signal noise as well as
the control pot signal.  Nothing that I tried would clean up the signal
enough (filter capacitors and RF chokes).

Perhaps if you use a *really* slow op-amp though...

Steve Jahr
jahr@hprnd.rose.hp.com