Consider doing the mixing in te transmitter.  You can connect the pots to the A/
D
inputs of a pic and use some of the new digital pot ICs to connect to the
transmitter.  Basically put your PIC and output circuit in between the radios po
ts
and the transmitter.  This will allow you to put another pot on the transmitter
to
adjust the amount of mixing.

Mario I. Arguello wrote:

> Hi folks,
>
> I realize there is Radio Control equipment out there that have what they call
> REVO. MIXING, for v-tail airplanes and mixing of helicopter collective and
> tail servos. The mixing is incorporated in the tranmitter though and it is
> available in expensive computer radios.
>
> I want to use a standard 4 channel radio TX /RX  with ,hopefully a homebrewed
>  external mixing circuit that will allow me to mix the control of two servos
> via one of the receiver's channels say ch1 for instance, while allowing me to
> have independent control of the second servo via ch2.
>
> A truth table would look something like this:
>
>         TX            RX
> CH 1 stick fwd/bwd    CH 1 and CH 2 on (servo 1 and Servo 2 move at same time)
> CH 2 stick left/right    CH 2 on (servo 2 only)
>
> In between the mixing circuitry of CH1 and CH2 I want to have a pot to make
> fine adjustment to CH2' servo throw.
>
> Can this be done with a PIC or simple IC  logic? that uses RX Bat of 5 v DC?
>
> Please let me know ASAP.  It is a problem that is keeping me awake at nights.
>
> Mario