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DIY Linear Actuator design

Discussion in 'Motor actuators and drivers' started by wannabeaflyer2, Mar 5, 2016.

  1. ferslash

    ferslash Active Member

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    talking about limit switches... once a limit switch is reached... it turns the motor off... and then...?? what... you have to manually move the rig so the motors can work again... or is there a way to allow the motors to got back "automaticlly" to a safe position once the limit switch is activated? (i hope i made my self clear... as you can see english is not working well today.... :D)

    fer
  2. yobuddy

    yobuddy Well-Known Member Staff Member Moderator SimAxe Beta Tester SimTools Developer Gold Contributor

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    I believe the idea is, it will only cut the motor from running in the direction of the limit switch.
    yobuddy
    • Agree Agree x 1
  3. luky_90

    luky_90 Member

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    hi guys, this is the scheme I use for the project of the actuators, where should I put the microswitches?
    on the engines you told me not to put them I would have too high power returns, where do you recommend me?

    Attached Files:

  4. Pierre Lalancette

    Pierre Lalancette Sir Lalancelot Gold Contributor

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    You are missing a part between the vnh5019 and the motor (it could also be between the PSU and the vnh5019 also). Its a high current relay. It will cut the power to the motors if one of your limit switch is triggered. I plan to do a closed circuit with all my limit switch. If one of them is triggered, every high power relay will be turn off and all of my 6 motors will shut down. I will have to find the cause, reset positions, and start again. Also, a panic button will be part of the limit switches closed circuit.
  5. bruce stephen

    bruce stephen Hammer doesnt fix it, must be electrical

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    The sabertooth 2x32 seems a better value than the pololu vnh5019 at $50.00 each. Are you getting the vnh5019 for less somewhere?
  6. luky_90

    luky_90 Member

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    no I have not found the VNH5019 unless, but I'm very comfortable with this card and even if it costs more I continue to use it.
    as soon as I have time I will also try the sabertooth.
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  7. Jerry Atrick

    Jerry Atrick this is my sim Gold Contributor

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    Hi wannabeaflyer2, I'm thinking of having a stab at a actuator, and would like to know something about lead on the ball screw, can you tell me what lead you selected and why please.

    This would be a real help, thanks in advance.
    Regards jerry.
  8. wannabeaflyer2

    wannabeaflyer2 Well-Known Member

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    hi @Jerry Atrick most of us here have settled on the 1605 ballscrew setup. meaning 16mm diameter ballscrew and lead being 5mm per revolution, I have not been to active here lately , its Flying weather but I regularly check to see what the guys are upto. Some great info to be found and many ways of making these actuators I dare say no 2 are the same so that's a good thing as it means its evolving all the time .. pick the bones out of the various and add your own slant to it , it helps introduce new ways of doing things ands we all benefit ... im lookin at encoders as Potentiometer replacements so watch this space guys i'll have bits to play with soon as im waiting for then to be shipped ... never stop learning guys this forum brilliant melting pot of ideas with Can do attitude that's infectious :)
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  9. Jerry Atrick

    Jerry Atrick this is my sim Gold Contributor

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    Hi and thank you for the info, any help is appreciated; will look forward to the encoders.

    Regards Jerry.
  10. haribole

    haribole New Member

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    Hello Peacemaker105, did you end up using the sabertooth 2X32A for this motor?
  11. wannabeaflyer2

    wannabeaflyer2 Well-Known Member

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    Hi Guys He's 'back as mentioned somewhere in my posts I have had this bee in my bonnet about swapping Pots for optical encoders for feedback on my actuators . well the new journey begins I have now bought Thanos's Encoder2Pos Interface PCB with the intention of doing some trials before commiting to changing out my current ( yes its Still in one piece Pride of joy 6DOF sim ) in my sim room .
    I may well start another Post for this part of the project but here is the target Outline ..
    I'll be using 600cpr Optical encoder ( already had those)

    Each actuator will need 1 Encoder2pos Interface PCB ( Simplist term it Converts Digital Pulses form encoder to Analog Output Suitable for Sabertooths and Barebones Kickstarte AMC Controller

    one Barebones AMC128USB Controller Card

    My spare Linear Actuator fitted with Limit switches and Suitable Gt2 Gear Pulley Ration 1:1 to Drive the Encoder via Looped GT2 Belt ( No Place to Mount Encoder directly to the shaft in this setup :-(

    Initial Trials will use BFF software But followed quickly by Simtools and SMC to cover my Options

    Not been active here for a while so its gonna be painful trying to pick up all the new info you guys have posted as things have moved on at a great pace .. but that's the plan ..

    I have attached some tatser picys but will add nes cad drawings and wiring diagrams as I go along

    1. Just waiting for the gears and belts to turn up then I can make the mounting plate and start connecting wiring
    All togather NOW shout out all Hail Blue SMOKE LOL fat finger freddy is on the case...as they say on THUNDERBIRD or was that STINGRAY " Stand by for action,, (drumbeat here ) anything can happen in the next half hour :) (its an UK thing LOL

    Attached Files:

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    Last edited: Jun 19, 2018
  12. Pierre Lalancette

    Pierre Lalancette Sir Lalancelot Gold Contributor

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    That thing force a lot of new electronic into the mix, but I don't think you're scare of that.

    Good luck and keep us posted. Glad to see you back.
    • Like Like x 1
  13. SeatTime

    SeatTime Well-Known Member

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    Mate - your soooo yesterday.. :p. Interested to see if it makes much of a noticeable difference. Keep us updated.
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  14. Thanos

    Thanos Building the Future one AC Servo at a time... or 6

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    Don't forget to update to the last firmware. It has some additional goodies for the encoder2position modules...

    https://www.dropbox.com/s/v9y8cjo5zhlhurx/enc_6dof_AMC1280USB_v2.4_rev7_debug.hex?dl=0

    The actuators should move up (limit H) and then down (limit L) to complete the calibration. If not, change the motor direction from the lcd menu (6dof direction).

    Thanks
    Thanos
    • Informative Informative x 2
  15. wannabeaflyer2

    wannabeaflyer2 Well-Known Member

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    Hi Guys more bits trickling in via ebay so fingers crossed weekend should see some headway test setup wise at least , just some more Pic's showing todays tweaks to the cad Model ..

    the 2 x 40Tooth GT2 Gears will be bored out 12mm for motor and 6 mm for Encoder , that'll be tomorrows lunch time mission :)

    will try to document as much of the setup and lesson learnt so hopefully others can see how this thing will pan out.

    attached CAD pdf for visualisation but I have 2 schemes for encoder connection ..
    Option A would be straight swap out for pot and use the existing belt arrangement
    Option B would be the Gear on motor and Encoder with 1:1 ratio

    will need to breadboard the ULN2803 chip initially but further down the road both the encoder and that chip will be mounted somewhere on the actuator to sort of make it self contained ( I stress Sortta) ..

    it appear I need to flash a firmware update so that will be my 1st item in the new posting ... have to ask general uestion ,,would you guys prefer a separate post as this is now Control system area as opposed to tacking it onto this post which was initially just to cover the mechanical assembly of an actuator ??

    Attached Files:

  16. Thanos

    Thanos Building the Future one AC Servo at a time... or 6

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    Hey, you don't need to use the ULN2803 mentioned on the schematic, this is used to relay the limit switch signal to the Servo drives for their internal function and disable the motor from moving to that direction.

    2018-04-01T19_30_46.020Z-Encoder2Position schematic.JPG

    The limit switches are used primarily to detect the travel length of the actuator and remap the encoder pulses correctly to the length of stroke.

    Thanks
    Thanos
    • Informative Informative x 2
  17. bruce stephen

    bruce stephen Hammer doesnt fix it, must be electrical

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    I'm using encoders 1:1 direct to the motor shaft then driving the system with kangaroo and sabertooth. the motion is handled by the kangaroo without converting the encoder to analog. Be sure your not just converting the signal to analog it kinda defeats the purpose IMHO. At that point its not really any different than just using a pot. The main reason I got rid of the pots are the fact that the encoder fits directly to the motor shaft and along with the kangaroo, they completely eliminate the need for belts, pulleys, gears and limit switches. Follow the KISS rule and you will be good(Keep It Simple Stupid).
    Last edited: Jun 22, 2018
  18. wannabeaflyer2

    wannabeaflyer2 Well-Known Member

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    Hi @bruce stephen yeah would have to agree to an extent , I tried the Kangeroo way way way back in the early days when I was using the Electric wheelchair motor and gear boxes for my 1st attempt at 6DOF had issue with getting the teach tuning to work with the Encoders major pain at the time , but as I said it was a newly introduce ed device to DE product range so I guess I suffered from lack of product knowledge syndrome and gave up in the end ...I still have all my Kangaroos but never got round to revisiting that setup...there's a lot to be said for the KISS method but hell its a challenge ( said with Peter sellers inspector Clousoe imitation French accent ) :) high praise for your work mate been checking it out big time :) just rechecked some info and the Encoder2pos interface seems to do a similar job to the Kangeroo in so far as both systems get taught the length of travel via limit switches and then use this remapped span to produce the analoug 0-5 v range .. take that explanation with a pince of salt as im just feeling my way into this test setup.. :)
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    Last edited: Jun 23, 2018
  19. wannabeaflyer2

    wannabeaflyer2 Well-Known Member

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    ok mini update , the easy part the mechanical assembly is done and I have configured the actuator to have both Encoder Position option already fitted , that way I can evaluate each option and settle on the final position depending on how the tests go .. some picys again just for reference

    Attached Files:

    • Like Like x 4
  20. bruce stephen

    bruce stephen Hammer doesnt fix it, must be electrical

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    First off let me say that without your work (and others) I wouldnt have even started down this road so tyhug:.
    The tune has been improved with the kangaroo. if you have them already i would give them a shot. they may need to be updated tho. I don't believe the kangaroo converts to analog. it does allow for analog input but i haven't tried that I just use encoders with reference.
    Were you using pots or encoders the last time you attempted the kangaroos? also I use physical stops to tune the kangaroo, not the limit switches. it doesn't hit at full speed or power so it shouldn't kill your assembly. I look forward to your progress keep us posted. ;)
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