DX6i and Servo Movement Limits

[mybad]

I just noticed something that has me a bit confused.

On my 3 Ch SC, I set 100% aileron>rudder mix so that I would control the turns with the right stick. So far so good. It is working great. ;D

Of course, I can move the rudder with either the aileron stick or the rudder stick if I want to.

And, I noticed that if I move them BOTH in the same direction, the rudder moves even further than if I move either by itself. That makes sense too.

But what confuses me is the TOTAL RANGE OF MOTION (total servo travel). If I move EITHER the rudder or aileron stick as far as it goes, the rudder moves a certain amount. But, if I move them BOTH, the rudder moves even further. Why is that? I assume that if I give full right rudder, then the rudder servo would move as far as it could in that direction. Apparently that is not so.

Am I moving the servos further than they should go?

Does this have anything to do with the fact that on the DX6i you can set the TRAVEL ADJ past 100%? I never did understand that.

[flydiver]

I don't know why the combined input would be more than the single input on the DX6i.
Mixing that way is additive? Dunno.

I do know that you can push the travel past the 100% mark. How much is a function of the particular servo (brand and model) and the TX as it defines the signal output. 110% is generally quite safe, 120% is likely safe. Once you get beyond that you may be into the area of possible damage. To really know you need something that measures amp draw at the servo level-it will climb rapidly when it hits it's limit. You can approximate that with VERY CAREFUL observation of 'hitting a physical limit'. Then back off a bit.

Mostly it's more prudent to get the travel about where you want it with mechanical adjustment and then fine tune it from the TX.

[rocketdork]

New to the board, and the hobby too...

I have a DX6i and have found some of the same frustration that you have.

Basically, the range of travel is an "ours goes to 11" kind of deal. At 100% of travel, the DX6i is not moving the total distance the servo can go. When you increase to 125%, the total distance is reached.

I put a receiver that was bound to my Tx on an oscilloscope. A normal servo output servo signal is a pulse that varies from 1 to 2 milliseconds and repeats every 50 milliseconds. I don't recall the specific numbers, but at 100% travel adjust and full stick, the pulse was not 2mS long, but less than that. Adjust to 125% and the 2mS pulse was there.

Make that channel a mix with another (dual ailerons, V-Tail, elevons) and the transmitter reduces the signal even more. Full input to BOTH channels (stick to a corner) will reach the 100% mark of ONE non-mixed channel. If I remember correctly, the full input on one mixed channel was about 1/2 of full range of a non-mixed channel.

I believe that the DX6i assumes that 2mS is the the max range and it won't exceed that number. All mixes and travel adjustments will total to a maximum of 2mS pulse width, or a minimum of 1mS pulse width. 100% is actually less than full travel, and 125% is full travel. Basically they arbitrarily chose a travel and called it 100%, then let you "exceed" that "limit" and you have a "ours goes to 11" kind of thing.

A couple of other non-obvious gotchas.

Sub trim is a PRE mix adjustment. If you have servos mixed, you MUST adjust both separately in the sub trim, if you choose to use it.

Normal trim on the front panel is a POST mix adjustment. Both mixed servos are adjusted.

Front panel trim is a center point adjustment ONLY. Where ever you have the travel adjust points set is where it will stop moving. When you trim a channel, you will increase travel from center in one direction, and reduce it in the other. Sub Trim moves the center AND the end points and equal travel is maintained, up to the maximum (2mS or 1mS) travel of the servo.

Travel adjust is actually an END point adjustment. There are two ends to the travel, both ends must be adjusted independently. To do so, you must move the stick for the servo you are adjusting in the direction you want to adjust. There are little arrows that indicate the direction of adjustment.

Travel adjust is PRE mix. Each Servo must be adjusted independently. In the elevon mix, you have to move the elevator stick to adjust one of the elevons...this will define how far it moves as an aileron too...likewise, you'll have to move the aileron stick to adjust the other elevon, this will define how far it moves as an elevator too.

My DX6i was out of calibration too...I found the calibration procedure online and used it...WOW what a difference, it was WAY off.

All of this effort was the result of a Flying wing that wasn't handling very well. It would roll at about 3 per second one direction and about 1 roll per second the other...it drove me NUTS. I think I finally have it figured out, but it took me a couple of months.