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Author Topic: servo movement  (Read 381 times)

Rob47

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servo movement
« on: March 24, 2020, 05:32:46 PM »


I am trying to run an aircraft side lift by using two 360deg servos, each lifting two chains attached to the lift.  I have tried having them running same direction which is the least successful way, have put a servo reverser in and managed to have them going opposite directions, problem is they twitch and start moving thus putting strain on the lift or one goes faster thus making a wonky lift.  So any ideas how I can achive the level operation of the lift.


Bob
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DaveM

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Re: servo movement
« Reply #1 on: March 24, 2020, 06:16:43 PM »

Bob
You'll have great difficulty running two motors at exactly the same speed (unless maybe they are stepper motors, about which I know very little). My approach would be to use one highly-geared motor, turning both sprockets through a common axle. A relay-based twin switch like the ACTion P44 will allow you to run the lift both up and down. MFA do a series of geared motors https://mfacomodrills.com/gearboxes/gearboxes.html
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Rob47

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Re: servo movement
« Reply #2 on: March 24, 2020, 06:36:36 PM »


Dave
I think I have more chance with two motors than the servos and extra electronics of the reverser, as I seem to be stuck in doors for a while great chance to experiment.


Bob


Bob
You'll have great difficulty running two motors at exactly the same speed (unless maybe they are stepper motors, about which I know very little). My approach would be to use one highly-geared motor, turning both sprockets through a common axle. A relay-based twin switch like the ACTion P44 will allow you to run the lift both up and down. MFA do a series of geared motors https://mfacomodrills.com/gearboxes/gearboxes.html
Dave M
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Taranis

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Re: servo movement
« Reply #3 on: March 24, 2020, 06:41:37 PM »

Another possibility would be to put each servo on its own channel so they can be individually trimmed and combine both channels on one switch or stick
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microgyros

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Re: servo movement
« Reply #4 on: March 24, 2020, 09:34:17 PM »

You only have, and always require, an eyeball on a continuous rotation* servo.
 Is that what you are using, Bob?

Trim implies position control which requires some sort of measuring device.
A quarter turn servo, 1.5, 2, 4 or 6 turn sailwinch retains the original rotary potentiometer that keeps position in check.  A servo slower can then slow the winch down to a scale rate.



* Continuous rotation servo is a misnomer. It is just a geared motor with a crude speed control.
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Rob47

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Re: servo movement
« Reply #5 on: March 24, 2020, 10:43:22 PM »


Yep that's what I am using, annoying thing is I have managed to trim them out so no movement at all, then when I switch off and then back on again its back to square one.  Been playing with motors on an esc and the results look good, and having only to cover 3" think that is my way forward


Bob


You only have, and always require, an eyeball on a continuous rotation* servo.
 Is that what you are using, Bob?

Trim implies position control which requires some sort of measuring device.
A quarter turn servo, 1.5, 2, 4 or 6 turn sailwinch retains the original rotary potentiometer that keeps position in check.  A servo slower can then slow the winch down to a scale rate.



* Continuous rotation servo is a misnomer. It is just a geared motor with a crude speed control.
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microgyros

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Re: servo movement
« Reply #6 on: March 25, 2020, 12:32:53 AM »

Yep that's what I am using, annoying thing is I have managed to trim them out so no movement at all, then when I switch off and then back on again its back to square one.  Been playing with motors on an esc and the results look good, and having only to cover 3" think that is my way forward


Bob
You would likely be adding a glitch filter which would show improvement if the continuous rotation servo did not have the capability.
I would go down the 10 multi turn winch + "servo slower" road.
It's all here:- https://www.google.com/search?&q=feedback+control+system
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C-3PO

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Re: servo movement
« Reply #7 on: March 25, 2020, 08:19:44 AM »

Hi Bob,

What are you going to use to control/switch the lift? - are you intending to switch it from your radio transmitter handset (raise / lower)?

DaveM's suggestion of using stepper motors would work a treat....in my experience slowing a servo always results is slightly glitchy/twitchy movement  - I have tried servos' analog and digital from 2 - 50

What scale is the model?

Regards
C-3PO


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malcolmfrary

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Re: servo movement
« Reply #8 on: March 25, 2020, 08:46:54 AM »

Multi turn sail winch, string, pulleys.  A two turn winch with a 1" drum gives about 6" of travel and is smooth.
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Rob47

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Re: servo movement
« Reply #9 on: March 25, 2020, 10:05:58 AM »


Hi C3PO, latest plan is to use two electric motors with shafts holding the two cycle style chains per end, this controlled by esc from tx, so far bench results are good, with the biggest issues resolved i.e. switching on and off and loosing settings fixed, so hopefully all is ok.  She is 1/96 which give overall length of 9 foot.


Bob


Hi Bob,

What are you going to use to control/switch the lift? - are you intending to switch it from your radio transmitter handset (raise / lower)?

DaveM's suggestion of using stepper motors would work a treat....in my experience slowing a servo always results is slightly glitchy/twitchy movement  - I have tried servos' analog and digital from 2 - 50

What scale is the model?

Regards
C-3PO
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C-3PO

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Re: servo movement
« Reply #10 on: March 25, 2020, 11:41:51 AM »

Bob,

Sounds like you are well on the way to a solution. If you get stuck and want to explore the stepper route very happy to help - total cost approx 15 for 2 steppers and a controller connected to your receiver...

I love 1/96th - lots of space for toys! Currently working on HMS Rodney @ 1/96th with my co-conspirator Peter Ward.

A future project of Peter's is HMS Hermes - this will hopefully have every whistle and bell with cherries on top with regards to functionality, animation & sound and light

C-3PO

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Rob47

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Re: servo movement
« Reply #11 on: March 25, 2020, 11:47:33 AM »


C3PO, thanks for the offer, could I ask you to run the stepper motor option past me in simple terms  :}   I have been following your Rodney posts, very informative, also built Hermes in 1/96 years ago, and have in storage Victorious at 1/72


Bob


Bob,

Sounds like you are well on the way to a solution. If you get stuck and want to explore the stepper route very happy to help - total cost approx 15 for 2 steppers and a controller connected to your receiver...

I love 1/96th - lots of space for toys! Currently working on HMS Rodney @ 1/96th with my co-conspirator Peter Ward.

A future project of Peter's is HMS Hermes - this will hopefully have every whistle and bell with cherries on top with regards to functionality, animation & sound and light

C-3PO
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C-3PO

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Re: servo movement
« Reply #12 on: March 25, 2020, 12:01:39 PM »

Bob - I have pm'd you my email address

Like the sound of 1/72nd Victorious- that must be a sight to behold...



Basic hardware as shown - some hook up wire to cable it together and some simple code for the little Arduino Nano (little circuit board) - could even incorporate micro switch limit controls.

One of the neatest things I have come across is the acceleration/deacceleration as the stepper starts/stops it's movement rather than a sudden hard stop - it looks and works superbly

Regards

C-3PO
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C-3PO

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Re: servo movement
« Reply #13 on: March 26, 2020, 09:58:35 PM »

The video shows the movement of two independent steppers

Total cost than 5 - 15 depending where you purchase components including controller (could have been purchased for 4.87 from China - sure this will all have changed in the future!)

Speed and distance travelled all configurable

https://www.youtube.com/watch?v=yhc5IezyfFM



https://www.youtube.com/watch?v=yhc5IezyfFM

C-3PO
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