X9D+ S3 multi-position switch

[glacier51]

Hello:

I traded off some gear for a friend's Taranis +. It's my second one so know enough about it. I installed a short 3pos switch on the case and soldered the switch into the S3 board holes. Went to the radio hardware page and calibrated the radio and set the S3 to multi-position switch.

Everything's working fine until I put the S3 switch into the mid position. It shows all positions OK, but if I twist the S2 knob, that input effects the S3 output. And the S2 input is backwards in the S3 output - twist S2 left results in a higher PWM value in S3.

First I thought was I had wired it wrong. Checked that was OK. Then I thought my solder job was crap and had a short, but the wiring looks good without any wire strands touching the other terminals.

I have re-calibrated a few times and I do notice that when the calibration is over, the S3 calibration bar isn't presented any longer and I have to use the hardware page to re-set S3 to multi-position switch, after which it works normally by itself.

I suppose switch could be bad. It's out of a X9D and was functional in that radio and in this Plus model.

Another thing I checked was changing models to see if I somehow had some mix or model setting upsetting things. Nothing there to indicate something else going on and changed models with the same effects.

Running OpenTX 2.3.11N401

Any thoughts appreciated,
Ron

Happy and safe New Year to all

 

[Kilrah]

The S3 input is for an analog control, not a switch. When your 3-position switch is in the middle the input is unconnected and floating which makes it do random stuff.
You need to fix the middle level with a resistive divider if you want to use a simple switch.

 

[glacier51]

Hello:
A couple of things: Why does OpenTX offer an S3 setting as "multi-position switch" for S3 then? Second is, the 3pos switch installed works correctly(it is biased off center slightly high) for the 3 positions.

Next is, I have a 3pos switch in the S1 position with resistors across the 3 poles, so am familiar with what you said. I assumed by having OpenTX say S3 can use a multi-position switch, it would work natively. I'll plan on adding the resistors to the S3 switch.

Any idea why the S2 knob would have the effect it has on the S3 mid position?

Happy New Year.

 

[Kilrah]

Why does OpenTX offer an S3 setting as "multi-position switch" for S3 then?

Precisely because it's an analog input that can accept 2-6 position switches set up with a resistive ladder, typically this one

FrSky 6 Position Mode-Flap Switch

Upgrade your Taranis with this 6 position mode switch. Replaces one of the pots near the top of the radio.

alofthobbies.com

Any idea why the S2 knob would have the effect it has on the S3 mid position?

That's exactly what happens when the input is floating, S2 sets the ADC sampling cap to a certain voltage, the radio samples that, then the radio switches to the S3 ADC channel and if nothing is connected nothing will change the ADC cap's voltage so it'll just read about the same again.

So while you seem to have intended to bias it correctly something's not right