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Author Topic: Digital Switch Setup and Flight Modes  (Read 78 times)

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Offline Deerslayer

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Digital Switch Setup and Flight Modes
« on: April 15, 2018, 08:50:10 AM »
I have owned the DX9 for about a hundred years (as my late friend Flypaper would say!) and am still discovering what certain things do and can be used for. Here is one situation that presented and which a simple combination of Flight Modes and Digital Switch Setup functions provided the solution. This is applicable to any of the DX-series, later generations of transmitters, which run the common Airware operating system.

The problem was, the Vector flight controller/stabilizer in my plane has a large selection of Modes. You can select up to 5 Vector modes (not to be confused with Flight Modes, which pertains only to the transmitter setup.). These can be assigned to one or more switches, commanding a specific channel which is connected from the receiver to the Vector.
Setting up 3 conditions on a 3-position switch is easy, but I wanted to use 6 position across two of my switches. As well, I wanted settings of these two switches to be mutually exclusive.

First, you need to understand the Vector's Mode protocol. They look at the Mode channel and enable 1 of the 5 possible Modes depending upon what is the pulse length. Don't worry about how you figure out how to convert Pulse width to the % values the transmitter shows, I will explain it later on.
Here is the table showing which Mode the Vector is in, as determined by the Pulse width
1 < 1250 microseconds
2 1250 - 1400
3 1400 - 1600
4 1600 - 1750
5 > 1750

Now, a word about Flight Modes. I have a very simple set of Flight Modes for this aircraft - only 3, so it only requires one 3-position switch. they are 1,2 an 3, which I call Normal, Cruise and TO/GA (takeoff/go around). Certain control mixes may, or may not, be enabled when each Flight Mode is selected. When I establish the Mixes for my two 3-position Vector Mode switches, I select which Flight Mode(s) will enable that switch and, therefore, the 3 Vector Mode settings allowable within that Flight Mode.

I use the GEAR channel for my Vector Mode. As with all my aircraft, a Channel Assign moved control of that channel away from the default A switch, as that is my Throttle Cut; I assigned the Gear channel to the F switch.

Now, I have already created the 3 Flight Modes, so it is time to set up the Mixes. 
1 = Normal   No Controls mixing
2 = Cruise    No Controls mixing
3 = TO/GA   Lots of Controls Mixing (for Crow, etc.)

Next, comes the Digital Switch Setup. Digital 2-position and 3-position Switches by default have  +100, 0, -100% as their command outputs, Digital Switch Setup allows you to change each of these individual positions to anything from 0 to 150%. I want my switches to operate in the Normal and Cruise Flight Modes, as follows:

Switch E -
Pos 0  = Vector Mode 1 = Loiter
Pos 2  = Vector Mode 2 = 3D Heading Hold
Pos 3  = Vector Mode 3 = OFF
Switch F -
Pos 5  = Vector Mode 5 = RTH TEST
Pos 4  = Vector Mode 4 = 2D Heading Hold
Pos 3  = Vector Mode 3= OFF

So, within the Digital Switch Setup, I have set Switch E to have 0, -45 , -100 as its three positions and Switch F as 0, 45,100 as its states. (I have already translated the requires Pulse widths to determine the +-45% settings.

Then, we set up two simple Mixes:

Switch E is mixed to GEAR  with its default 100,100 values,  active in Flight Modes 1 (Normal) and 2 (Cruise), disabled in 3 (TO/GA).

Switch F is also mixed to GEAR exactly as with Switch E.

Now, in either the Normal or Cruise Flight Modes with both Vector Mode (E & F) Switches in the Down position, the Gear channel is outputting  the "0" or Centered command, so the Vector is in its OFF Mode. In TO/GA Flight Mode, these two Switched are inoperative and the Vector is in OFF. This means that, at any time, pulling both E and F back will turn the Vector OFF, regardless of Flight Mode.

This is simpler than it may sound. This particular need and the specific settings of Switches is just one example of what can be done with two very powerful functions on Spektrum and other systems, once you get the basic idea. I have done a lot of Mixing, etc. across many aircraft of different types and with varying setups, yet I am still learning new stuff all the time.

If this gives anyone some ideas or questions, please let me know. I may be able to help you, or at least point you in the direction of someone who knows a lot more about it and is very patient and willing to assist.

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Addendum - Translating % to Pulse Width

Spektrum defaults to Pulse Width range of 900 to 1900 as -100% and +100%, respectively.  You can set Servo Travel to as high and low as -150% and 150%, respectively. Pulse Width = 1500 is 0%, or Center, regardless of the range setting. For my Vector control example, I Ieft them at the defaults.

My test setup consists of a receiver, digital servo tester and servo attached to a degree wheel. The latter is just for interest, only the receiver and digital readout on the servo tester is required. For this test, and in the eventual aircraft setup, make sure that there is no unwanted Mix or Trim settings lurking in the background to interfere with your required operation. (Experience speaking here!)

Pulse Width = 1500 is 0%, or Center, regardless of the range setting.

I set up my test channel such that it was on the Throttle, as that enables more precise adjustments which stay in place while taking various readings. In the Trims menu, I had set Throttle Trim to "0", to ensure that I got clean readings, with only the stick movement. From there on, it is simple:

1. Go to the Monitor screen on the transmitter.

2. Set the throttle stick in various positions, taking readings of both the % on the transmitter and the Pulse Width microseconds on the servo tester. If you are really interested, as I was, plot them and convince yourself that they are linear, and/or  have your servo degree wheel hooked up and watch it wiggle around. Do not worry if the digital readout is slightly different from expected; mine read 17 microseconds high at the Center and the endpoints, I do not know why, but it is a trivial error.

3. My Vector modes required it seeing the following Pulse Widths:
1 < 1250 microseconds
2 1250 - 1400
3 1400 - 1600
4 1600 - 1750
5 > 1750
So, via Digital Switch Setup, I set Switches E and F to have "0" at their same position, pulled fully back. That gives Mode 3 on both.
Then, I set Switches E an F to be at -100 and +100, respectively, in their furthest forward positions. Modes 1 and 5 are now taken care of.
Mode 2 and 4 are the ones where you need to know the correspondence between % and Pulse Width, as these activate within narrow ranges of values. I found that +-45% values were fairly centered within these required values, so those will be the Switch midle positions.

Therefore, my Digital Switches are set up as E = 0, -50, -100 and F = 0, 50, 100.

The servo tester with a digital readout is my most valuable gadget in the shop or at the field. This is one example where it was essential. I use it to check out every new servo immediately after purchase and every servo prior to, and immediately after, installation in an aircraft, or when a malfunction occurs or is suspected. Get one for yourself!
My purpose in Life is to serve as a Warning to others