"Weight" vs "Limits"

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dsa44
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"Weight" vs "Limits"

Post by dsa44 » Sun Feb 12, 2017 4:52 pm

Just trying to wrap my brain around these issues.

I have a servo that moves too far and the arm hits the mounting when set at 100 weight and -100 to +100. I can easily modify the limits to -75 to +75 leaving weight at 100 and movement is fine (loosing 12.5% on either end for total 25%).

I can also change the weight to 75 (loosing 25%) and leave the limits at -100 to +100 and it seems to accomplish the same thing.

Is one better than the other??
Thx again.

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jhsa
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Re: "Weight" vs "Limits"

Post by jhsa » Sun Feb 12, 2017 5:55 pm

In my opinion, in your case, the servos arms are hitting the mounting, so that can eventually damage them. The limits are exactly what they say. Some hard limits, that means the servo will NEVER pass that setting.
if you leave the limits at 100% and decrease the movement in the mixer, it will work the same way until something happens ( like some other mix you might program on the same channel) that will drive the channel over the safe 75% setting. The servos will then hit the mounting again.. If you use the limits, even if the mixer tells the servo to move that far, the limit won't let it..
I for example, use the limits to find the max allowed movement for every single servo.. Then use the mixer and/or the Dual rate menu to adjust the controls movement.. Some other people might do it differently..

João
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Daedalus66
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Re: "Weight" vs "Limits"

Post by Daedalus66 » Sun Feb 12, 2017 6:23 pm

Plus one on that. Also:

Limits of 75 are exactly what they say: 75. That's 25 less than 100, not 12.5.

dsa44
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Re: "Weight" vs "Limits"

Post by dsa44 » Mon Feb 13, 2017 10:20 pm

jhsa wrote:In my opinion, in your case, the servos arms are hitting the mounting, so that can eventually damage them. The limits are exactly what they say. Some hard limits, that means the servo will NEVER pass that setting.
if you leave the limits at 100% and decrease the movement in the mixer, it will work the same way until something happens ( like some other mix you might program on the same channel) that will drive the channel over the safe 75% setting. The servos will then hit the mounting again.. If you use the limits, even if the mixer tells the servo to move that far, the limit won't let it..
I for example, use the limits to find the max allowed movement for every single servo.. Then use the mixer and/or the Dual rate menu to adjust the controls movement.. Some other people might do it differently..

João
Roger that! Setting the control arm movements with the "limits" is the best way to go so they never exceed the point where they will knock into and damage the mounting.
Thx DSA

dsa44
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Re:

Post by dsa44 » Mon Feb 13, 2017 10:21 pm

Daedalus66 wrote:Plus one on that. Also:

Limits of 75 are exactly what they say: 75. That's 25 less than 100, not 12.5.

Yes indeed! What I meant was 12.5 on either end, total of 25.
Thx DSA


Daedalus66
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Re: "Weight" vs "Limits"

Post by Daedalus66 » Mon Feb 13, 2017 10:52 pm

You're misunderstanding limits. Limits of 25 mean 25 on each end. At 100% the pulse ranges from 1100uS (-100%) to 1500uS (0%) to 1900uS (100%).

At 75% it goes from 1200 (-75%) to 1500 (0%) to 1800 (75%).

Total doesn't come into it.

dsa44
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Re: "Weight" vs "Limits"

Post by dsa44 » Mon Feb 13, 2017 11:19 pm

I get the concept you are saying. I was just trying to make it linear in my mind. Setting the limits from -100 to +100 to -75 to +75, the range of value goes from 200 to 150. 150 is 25% less than the normal 200 settings, and thereby limiting 12.5% on either end.
Cheers

Daedalus66
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Re: "Weight" vs "Limits"

Post by Daedalus66 » Tue Feb 14, 2017 5:28 am

The original point was to compare the result of changing weight to 75 with that of changing limits to 75. The simple answer is they can do exactly the same thing but with different implications.

They both reduce the pulse length range from 1100 to 1500 to 1900 down to 1200 to 1500 to 1800. Notice that 1100 to 1500 is 400 while 1200 to 1500 is 300 -- I.e. 75%. This is what counts.

In terms of the reduction in servo travel the relevant number is 25 out of 100, not 25 out of 200 (12.5). Forget 200!

To put it another way, the relevant measurement is ultimately the physical throw on ONE side of a servo, not both sides.

The longer story was explained by João.

tonnie78
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Re: "Weight" vs "Limits"

Post by tonnie78 » Thu Feb 16, 2017 5:29 am

If you set limits doesn't that mean that the last 25% input from the stick doesn't make the servo move further? So the last bit of the stick movement doesn't do anything?

While the weight takes 75% of the stick input and send that to the output.

Both will limit your endpoint to 75% but with setting weight to 75% you keep a linear relation between stick and servotravel while limit, really limits your servo movement after the stick input gets over 75%?

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jhsa
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Re: "Weight" vs "Limits"

Post by jhsa » Thu Feb 16, 2017 9:17 am

Nope, 100% of the stick movement should be equal to the limit values, as long as the mixer is set to 100%.. Good way to find out, try it, very easy.. :)

João
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Kilrah
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Re: "Weight" vs "Limits"

Post by Kilrah » Thu Feb 16, 2017 11:12 am

Limits don't only limit, they also scale.

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