tomfiorentino

Guys,

My reading has told me that setting transmitter ATV to the highest setting maximizes servo resolution. The problem is that creates way too much throw no matter what I do (within reason) mechanically. So, if I end up taking some of the travel out by turning down dual rates...do I take the resolution back out?

In other words is 150% ATV with 25% Dual Rate the same thing as 37% ATV with 0% Dual Rate from a servo resolution perspective?

I'm feeling like this could be a totally dumb question....and by the way, not that my average piloting can tell the difference! I'm just trying to understand it...

I'm using a JR transmitter with Hitec 7955TG's with 1" arms.

Thanks,
Tom

dirtybird

My Feedback: (5)

Yes you lose. You cant have it both ways.

tomfiorentino

There is an upset.

Can cut and paste that to:

Marriage forum
Work forum
Life forum
Etc.

Tom

Bax

My Feedback: (11)

At the servo, a pulse of a given width is received that determines the amount of movement. Regardless of the transmitter setting, you need the same pulse to give the servo a given movement. Another way to think of it is this: For the full end-to-end travel with ATV all the way up to 150%, you have 150 "ticks". You want it to be 1/3 smaller, or 100 "ticks", so you adjust the Dual Rate to the setting that gives you that movement. If you set the ATV to 100%, you have 100 "ticks. So you get the same amount of travel.

Where the best resolution is needed, you set the ATV to the maximum possible, and then reduce the amount of control surface travel by moving the pushrod in at the servo horn. This reduces the amount of control surface travel and increases torque. Now, instead of 100 "ticks" of travel, you have 150 "ticks", which is higher resolution at the control surface.

You should be able to resolve this mechanically. If you have too much throw at the control surface, you shorten the arm at the servo and/or lengthen the control horn at the control surface. This is ALWAYS doable. If your control horn isn't long enough, then you can make or buy longer ones. If you think it cannot be resolved mechanically, look at the problem carefully to see why you think that's the case.

tomfiorentino

OK thank you...I get that.

Im all the way inside at the servo and all the way out at the horn. So, longer horns is an option..sure. It is an Aeroworks 260 and I am using the stock stuff.

Pehaps it is assumed that a 3D set-up with lots of throw is in order.

Thanks Bax....

Tom

BarracudaHockey

My Feedback: (11)

In a practical sense, I wouldn't get too worked up about it.

Rob2160

Another point to consider - if setting ATV to 150%, your servos will be moving more than 45 degrees in each direction at which point you really start losing linearity.

There is a nice explanation here http://rc.runryder.com/helicopter/ga...pt=LinearServo

What this means is the first 10% of stick deflection will give you more control surface movement than the last 10% of stick travel.

It is always present during any (rotary) servo travel but if extending the travel with 150% ATV the non linearity will become exponentially more prevalent. (Some radios can compensate for this directly), or another way is to use expo to ensure your control surfaces respond linearly to the stick inputs.

tomfiorentino

You and Barracuda have made practical comments, both of which matter more than any resolution..

Thanks for commenting...

Tom

BarracudaHockey

My Feedback: (11)

You also risk driving the servo to the mechanical stop if you have a mix added in and your control is near the end of throw.