Collective servo response

[jewslox]

A friend at my field mentioned that in the old days, radios had to give collective input one servo at a time. He says nowadays, radios send a signal to all three servos in the same 'packet' whatever.

So while I was leveling the swash on my new bird, I noticed if I gave a large pitch input, a servo would lag behind, making for an uneven transition. I thought it could have just been that the 4 AA batteries I was using wasn't supplying enough amps, but my BEC hasn't arrived for me to test it with my 6s lipo. Still, given what my friend told me, I'd have thought that the limit of amp draw would only make the response slower or something, not uneven. Any thoughts?

I have a Dx6i and standard digital servos for cyclic.

[surfespacio]

max current draw is a function of the circuits resistance, it's not a limitation of the batteries.

at 2.4 GHz, a 2.4 kB packet could be sent out theoretically a million times a second. i have no clue how the Dx6i's data stream is constructed, but whatever the data protocol, i think it's pretty safe to say that it's not the radio data stream because the same packet would be coming thru so many times, even during a simple stick movement.

even in the old days, packets sent one servo at a time, at 72 MHz, is mind numbingly blitzkreigingly fast compared to seeing a lagging movement on the swash with your eyes. and these control packets are probably only a few tens of bytes anyways, so you could still send packets at like kHz rates plausibly.

sooooo, i had the same problem when my servos were set up incorrectly...have you tried turning off mixing and/or reversing some channels?

v/r,

-Matt

[surfespacio]

oops, my bad, edit in a factor of ten reduction on my numbers for modulation losses...


-Matt

[jewslox]

They move the right directions, if that's what you're asking. But yes, I had to reverse one of the aileron servos and then reverse the aileron mix to get it working right. I'll check tomorrow, but maybe new batteries will fix it, though I still wonder why that would happen.

[mchammer]

What you are probably noticing in the swash is a type of interaction. If you move your cyclic fore and aft quickly you will probably notice the very center ball of your swashplate moving up and down slightly on the main shaft. Because your servos are 120 degrees apart, the one servo that is either in front or rear (depending on your heli) has the most mechanical advantage.ie, it has to move the least to get the most movement of the swash. the 2 servos on the sides of the swash have further to travel thus they cant possibly keep up with the first servo we spoke of. There are a few ways to overcome this. All of them are perfectly acceptable.

1. dont use a swash with 120 degree ccpm.

2. do use a swash with 140 degreee ccpm,no ccpm, or 90 degree ccpm

3. or use a radio that has the abillity to cancel out these interactions on 120 degree ccpm. Higher end radios do this very well by slowing down the servo with the most mechanical advantage on the swash at the propper times.

I am not familiar with the dx6 but I know the dx7 has a feature in the swash menu called expo. This is not expo as we usually know it.This helps to cancel out interactions in the swash. I remember on my old dx7 the manual said nothing of this. I discovered it in the manual for my JR x9303. In the dx7 it seemed to help although nothing like the x9303 or the 12x which has a really sweet system for canceling out swash interactions. If this feature is on your swash menu of the dx6 give it a try. All that said; does it make a big difference in the way the heli flys????? OOOOOOOO YES, night and day.

Hope this helps!