Taranis: Change S1 & S2 to Switches - RC Groups
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Nov 12, 2016, 07:31 AM
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Mini-HowTo

Taranis: Change S1 & S2 to Switches


If 3-position switches (short or long) are wired in parallel with the S1 and S2 potentiometers ("pots"), the pots are left in their center positions (very important), insulated, and stored inside the radio, and the switches are installed in their places, the following six additional switch functions will be available:

S1↑ S1− S1↓ S2↑ S2− S2↓ (Of course these designations won't show up on your radio screen or in Companion but they can be useful in your programming notes.)

Decoding S1↑ and S1↓ with Logical Switches:
Code:
L1	a~x S1  100 ---- 0.0 0.0 L1 = S1↑ 
L2	a~x S1 -100 ---- 0.0 0.0 L2 = S1↓
These two Logical Switches may be reversed, depending
upon which way the 3-position switch is installed in your radio.
If S1− represents a default setting then it might not need to be specifically decoded, otherwise it can be decoded with a third Logical Switch:
Code:
L3	AND !L1 !L2 ---- 0.0 0.0 L3 = S1−
The code for S2 is similar:
Code:
L4	a~x S2  100 ---- 0.0 0.0 L4 = S2↑ 
L5	a~x S2 -100 ---- 0.0 0.0 L5 = S2↓
L6	AND !L4 !L5 ---- 0.0 0.0 L6 = S2−
To wire a 3-position switch in parallel with a pot, use short insulated jumper wires to connect the top terminal of the pot to the top terminal of the switch, the center terminal of the pot to the center terminal of the switch, and the bottom terminal of the pot to the bottom terminal of the switch. Remember that the pot has to stay connected even though it won't be accessible, and it has to be set to the center detent position.

If you want to reverse the modification later it won't be necessary to disconnect or remove the switch. Just set it to its center position, insulate it, store it away inside the radio, and put the pot back where it used to be. Remember that in either case the control that's not being used must remain set to its center position.

Last edited by Miami Mike; Nov 14, 2016 at 11:17 AM.
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Nov 13, 2016, 04:16 PM
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This is an example where decoding S1− is not necessary.

I'm using switch S1 for aileron triple rates, and it happens that I can select all three rates using only two logical switches:
Code:
L9  a~x S1  100 ---- 0.0 0.0 (L9 = S1↑) 
L10 a~x S1 -100 ---- 0.0 0.0 (L10 = S1↓)
On my Inputs page I have three aileron rates designated AileHigh, AileMid, and AileLow, but AileMid is the last line and functions as a "catchall" so that the aileron stick is guaranteed to work even if none of the lines above it are active.

Code:
[I3]Ail
    Ail Weight(+90%) Switch(L9) [AileHigh]
    Ail Weight(+60%) Switch(L10) [AileLow]
    Ail Weight(+75%) [AileMid]
On the Inputs page, OpenTX uses the first line that's true for each channel and ignores what's below it.
Last edited by Miami Mike; Nov 14, 2016 at 11:22 AM.
Feb 09, 2018, 06:37 AM
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Update, February 6, 2018


Here's the logical switch decoding setup I finally settled upon and use today:



Code:
L9 S1 > 66
L10 S1 < -66
L11 S2 > 66
L12 S2 < -66
All of the radio mods and programming setups in my blog are developed with, and designed for, the FrSky Taranis Plus using OpenTX version 2.1.9. If you've adapted any of them to other radios or later OpenTX versions, or found a better way to do what I've described here, please feel free to describe your version or link to it in the comment section below the relevant post.

Mar 27, 2018, 11:22 AM
Registered User
Hello Mike:

I have a Taranis Plus. Added the S3 6pos knob on top of the case and replaced the S1 knob with a 6pos. I haven't had any luck with these knobs. They seem to loose their detent and now I can't program much of anything with the ms values. The present S1 goes from full high to center after 3 clicks, then full low with the remaining clicks.

I then replaced the S1 with a long switch, wiring it in the connector, but only get full high and full low. The center position responds at full low.

Another guy said to get the center position of the switch to work, there needs to be a resistor in the wiring, since the radio thinks S1 is a pot. You know anything about that?

I would like this stuff to at least be somewhat reliable and I find switches seen to last longer than the pots. Plus I really don't need all 6 positions of the knob.

Thanks,
Ron
Mar 27, 2018, 12:31 PM
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Quote:
Originally Posted by Glacier51
Hello Mike:

I have a Taranis Plus. Added the S3 6pos knob on top of the case and replaced the S1 knob with a 6pos. I haven't had any luck with these knobs. They seem to loose their detent and now I can't program much of anything with the ms values. The present S1 goes from full high to center after 3 clicks, then full low with the remaining clicks.
I've never done anything with 6-position switches except to try the settings in Companion. I see that if you enable them in General Settings → Hardware they show up as model setup choices and S3 appears in the simulator.
Quote:
I then replaced the S1 with a long switch, wiring it in the connector, but only get full high and full low. The center position responds at full low. Another guy said to get the center position of the switch to work, there needs to be a resistor in the wiring, since the radio thinks S1 is a pot. You know anything about that?
That's why I emphasized above that you should leave the pot in the circuit with the knob centered and wire the switch in parallel with it. Without the pot there need to be two resistors in series with the center wire connected between them, but the centered pot does the same job.
Mar 29, 2018, 09:03 AM
Registered User
Mike:

Went with the 2 resistor solution on both switches.

Getting -99, 0, 100 on one and -99, -33, 100 on the other. Same brand and package of 15k resistors.

Ron
Mar 29, 2018, 11:53 AM
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Perfect! 15k is a bit higher than what's normally used but that's fine as long as it works, and apparently it does.

It'll work fine that way if you use the decoding method in my post #3 above. If you want more precise output then just recalibrate your radio. It's still going by the values from when it was calibrated with the S1 and S2 pots, so the calibration now needs to be redone if you want outputs of -100% / 0% / +100%.

If you want to specifically decode the center position of a switch then use a logical switch like this one:

Code:
L3	AND !L1 !L2
Mar 29, 2018, 08:46 PM
Registered User
Hey Mike:

Thanks for the help.

Ron


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