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PICList Thread
'Radio Control Mixing function'
1999\08\20@010458 by Mario I. Arguello

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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

1999\08\20@052318 by Quentin

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"Mario I. Arguello" wrote:
>
> Hi folks,

> 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?
>
Of course it can be done with a PIC, what a question. :)
And I think you might just be able to squeeze it onto a 12Cxxx PIC.
Question: If you move Ch1 full up, and then move CH2, what will Servo2
do then?
Why do you need to make fine adjustments with a pot when you can just
use the subtrim of CH2 stick?

Quentin

1999\08\20@083915 by Andy Kunz

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>Please let me know ASAP.  It is a problem that is keeping me awake at nights.

Mario,

Yes, it has been done, and I believe they are for sale now.

My customer is http://www.rcboats.com and ask about the mixer on his e-mail
account.    We went through several versions with different mix ratios,
everything from 1:1 to 8:1 before we finally settled on the one he's using now.

With his permission, I _could_ burn you whatever mix you want.

Andy

==================================================================
Andy Kunz               Life is what we do to prepare for Eternity
------------------------------------------------------------------
spam_OUTandyTakeThisOuTspamrc-hydros.com      http://www.rc-hydros.com     - Race Boats
.....andyKILLspamspam@spam@montanadesign.com  http://www.montanadesign.com - Electronics
==================================================================

1999\08\20@110445 by Adam Bryant

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Hi Mario,
Yes it can be done.  I did it not too long ago with a 16C84 although I
never actually put it in an airplane.  IIRC the code was around 300-400
bytes so a 12C508 would be plenty of space (my code was terribly size
inefficient).  I also saw a design on the web somewhere (don't remember
where) by an Australian that used a 16C84 and a 6 or 8 position DIP
switch to select a mix ratio and even reverse the servo directions (in
case your transmitter doesn't have servo reversing).

You have 4 data lines that you care about: input from channel 1 on the
receiver, input from channel 2 of the receiver, output to servo A, output
to servo B.  (The Aussie was using the extra pin count of the C84 to read
the switches, so if you don't need the configurability, a smaller device
like a 508 would be fine).  The basic premise is to read the pulse width
of the incoming channels, do some simple math to mix the signals
together, trim the values you just calculated in case they exceed the 1
to 2ms pulse widths, then send the values out to the servos.

So my algorithm was:

1. Wait until channel 1 signal came on. Reset counter.
2. Wait until channel 1 went off. Store counter.
3. Wait until channel 2 came on. (Internally the receiver uses a shift
register or counter to send out the signals to the servos, so you can be
sure that channel 2 happens after channel 1). Reset counter.
4. Wait until channel 2 went off. Store counter.
5. Calculate output values. The "elevator" value gets copied to both
outputs, then modified by the "aileron" value.  The direction (+ or -)
depends on whether the aileron stick is "left" or "right".
6. Check to insure that your calculated values do not exceed the 1 to 2ms
pulse widths for the servos.  Trim these values if necessary.

I assume you want to use the pot for what is commonly called an "end
point adjustment".  In this case read the value of the pot (using an A/D
converter, R/C circuit or whatever) and take this value into account in
your calculations for the output values.

My design had some "jitter" in the output servos.  I never determined if
it was software related or power related.  I powered the PIC directly
from the receiver, but didn't do anything to filter the incoming power.
Put a cap (.1mf or so?) across the PIC power lines and also put a small
resistor between the PIC and the servo data lines.

Hope this helps,
Adam

On Fri, 20 Aug 1999 00:33:24 EDT "Mario I. Arguello" <MIADsgnsspamKILLspamAOL.COM>
writes:
{Quote hidden}

Adam Bryant (age 0x23)
.....abryantKILLspamspam.....peaktech.com (work)
EraseMEadamdbspam_OUTspamTakeThisOuTjuno.com (home)
Parker, CO, USA
Robotics, RC Airplanes, anything using a PIC

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1999\08\20@111519 by Mario I. Arguello

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In a message dated 8/20/99 6:24:41 AM SA Eastern Standard Time,
qscspamspam_OUTICON.CO.ZA writes:

<< Of course it can be done with a PIC, what a question. :)
And I think you might just be able to squeeze it onto a 12Cxxx PIC.
Question: If you move Ch1 full up, and then move CH2, what will Servo2
do then?
Why do you need to make fine adjustments with a pot when you can just
use the subtrim of CH2 stick? >>

Hi Quentin,
thanks for your fast response, I know it can be done with a pic, just that I
have never done any circuit design but I understand some electronics.

I want CH2 (Servo 2) output to follow CH1 (Sevo 1) in proportion  (MIX) by a
certain percentage adustable via a pot on the circuit board. Trims at TX are
centered and can also be used for further adjustmet but I want the % mix pot
on the MIXing board.

Example: I move CH1 (at TX) from full down to full up, CH1 (at RX) moves
servo 1and 2 end to end. But servo 2 follows only a certain % dictated by the
fine tuning or % adjust pot.

Also at any point weather it is full down or full up on CH1, I want CH2
(Servo) to move  full left and full right independently via CH2 (at TX).

Mario

1999\08\20@112107 by Armando Garcia Hernandez

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Hi

I'm a interested in the IR and RF, and I want to make a control with
16c84 to turn on something, I want the basics of the remote control, some
IC, code or algorithm that helps me to do my first step in to remote
control,
by sample, a circuit with 2 push buttons, ()on and ()off, with the
receiver...

some body could help me?

Thanks in advance

Armando

1999\08\20@133254 by Erik Reikes

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At 12:33 AM 8/20/99 -0400, you 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)

Elevons?

Servos are controlled with a simple pulse width modulation scheme.  A PIC
can easily control these there is information about this on the web :

http://www.icenter.net/~bev478/links.htm#Motor%20&%20Motor%20Control

that tells you how to talk to the servos.  If you just want two servos to
move simultaneously a simple Y connection should work.  i.e. hook them up
in parallel to the same channel.  Most hobby stores sell connectors to do
this.  If you want more complicated mixing, A PIC could decode the PW
signals from the receivers and map them to the separate servos as needed.

Good luck!

-E

1999\08\20@141648 by Dave Johnson

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>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.
There are fairly cheap, tiny external mixers available. For instance, see:

http://www.zagi.com/html/Wattage/wattage.htm).

That said, though, buying one isn't nearly as much fun as rolling your
own...

Dave Johnson

1999\08\20@213131 by felix centeno

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I've the same interest, I going to try first with a FM bug (small TX) and
like receiver a very cheap FM radio
using a serial comunication and  a LM567( Tone Decoder) like modem at 300
Bauds (Bell103 Standart),
Other way is the National 74VHC943 it is a fully complaint Bell 103 standart
modem ( I've 2 buy in  Jameco)
but I don't have the 3.57 Mhz cristals  for its.
Write me directly (in Spanish also) if you need help

Felix Centeno
@spam@fcentenoKILLspamspamiamnet.com



-----Mensaje original-----
De: Armando Garcia Hernandez <KILLspamarmandoKILLspamspamPORTHOS.UGTO.MX>
Para: RemoveMEfcentenoTakeThisOuTspamIAMNET.COM <spamBeGonefcentenospamBeGonespamIAMNET.COM>
Fecha: Viernes, 20 de Agosto de 1999 11:36 a.m.
Asunto: Re: Radio Control Mixing function


{Quote hidden}

1999\08\21@210110 by Brian Kraut

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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:

{Quote hidden}

1999\08\22@182632 by Quentin

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"Mario I. Arguello" wrote:

> Hi Quentin,
> thanks for your fast response, I know it can be done with a pic, just that I
> have never done any circuit design but I understand some electronics.
>
Mario, I was just making a jest, since you asked on the PIC list. :)

> I want CH2 (Servo 2) output to follow CH1 (Sevo 1) in proportion  (MIX) by a
> certain percentage adustable via a pot on the circuit board. Trims at TX are
> centered and can also be used for further adjustmet but I want the % mix pot
> on the MIXing board.

> Also at any point weather it is full down or full up on CH1, I want CH2
> (Servo) to move  full left and full right independently via CH2 (at TX).

OK, How about this:
The signal from the RX to the servo is a pulse 1000 to 2000 microsecs,
repeated every 20 millisecs. If the servo (thus the Ch on the TX) is
centered, then the pulse width is 1500 microsecs. You might know all
this.
So now you make the PIC read the pulse width of both CH from the RX and
the setting of the pot.
Servo1 can be directly connected to CH1 output from the RX, with a Y
piece connector (or on PC board) with the 2nd end to input CH1 signal
into the PIC, thus the PIC does not need to control servo1 (makes it
easier on the programming side).
The first 1000 microsecs of the signal is don't care, so measure only
the value of each channel after 1000 microsecs, so you have a reading of
0 to 1000 microsecs for each channel, then:
The pot is a value 0-100% of CH1 (call it PCH1)
See if CH2 is smaller or bigger than 500 microsecs. If smaller then
subtract (500-CH2) from PCH1. If the result is smaller than 0 (negative)
then make the result 0.
If CH2 is bigger than 500 then add (CH2-500) to PCH1, if the result is
bigger than 1000, then make the result 1000.
If CH2 is 500 microsecs, then the result is PCH1

Add 1000 microsecs to the result and run the servo.
voila! (I think, hehe)

Hope this helps
Quentin

1999\08\22@212759 by Mario I. Arguello

picon face
Quentin!

That's it!. Except I do not have the equipment to program a PIC :(.

I can cut my own PC board though from a schem. Can you help me out with the
PIC section as you described it? and a schem so I can make the board, or
maybe you have all the equipment to do so.   Tell me what components you need
and I will get them.

Thanks
Mario

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