Need Help! Drive a 1.8 degree stepper at 1 RPM - Page 4


Page 4 of 11 FirstFirst 1234567 ... LastLast
Results 61 to 80 of 206

Thread: Drive a 1.8 degree stepper at 1 RPM

  1. #61
    Registered
    Join Date
    Sep 2011
    Location
    uk
    Posts
    119
    Downloads
    0
    Uploads
    0

    Default

    Another good point, i am going to use a 9.8Ah battery so consumption needs to be kept to a minium especially for the himalayas as charging will be an issue most of the trip.
    I will try to set the motor current as low as possible as torque will not be a problem but to be able to cut power to the motor while the mount is still turned on will be a bonus.

    Ceefna



  2. #62
    Community Moderator Al_The_Man's Avatar
    Join Date
    Dec 2003
    Location
    Canada
    Posts
    24216
    Downloads
    0
    Uploads
    0

    Default

    You could output a drive disable from the PIC whenever the motor sees the home posn. or home input, turn it back on when a move command is issued.
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


  3. #63
    Registered
    Join Date
    Oct 2005
    Location
    Australia
    Posts
    2392
    Downloads
    0
    Uploads
    0

    Default

    Ok, I see a problem with your pivoted plates design as the relationship between motor speed and plate speed is NOT linear, it follows a tangent created by the size of the triangle at any point in time.

    It would be much better to modify the mechanical design so that the drive between the stepper motor and the moving plate is done with circular pulleys or gears (in the typical fashion) so circular motor movement causes circular plate rotation with a linear relationship between motor degrees and plate degrees.

    Secondly are you now saying you want to hike this thing up the Himalayas? Maybe weight (and that includes battery and motor weight) will be an issue?

    Anway I think the first thing to to redesign the mechanicals for circular rotation, it might be as simple as adding a lightweight Tamiya gearbox with a high ratio, driving a o-ring belt via 2 pulleys.

    I suggest a large diameter pulley for the camera plate to dampen any gear tooth effects caused by the stepper or gearbox. Also an o-ring belt won't have any cogging as you might get from a toothed belt and should be fine to drive the very light load of a properly balanced camera.



  4. #64
    Registered
    Join Date
    Sep 2011
    Location
    uk
    Posts
    119
    Downloads
    0
    Uploads
    0

    Default

    Hi please have a look at this production mount.
    http://www.youtube.com/watch?v=4WfIM9HeGPU]NEAF 2008 - AstroTrac TT320 - YouTube

    I can assure you that it works. These cost a mighty £500! My design is the same but I didn't show in my picture that the motor can pivot on the bottom arm, also the arms will only move 160mm apart to give 2 hours tracking so the arc is not an issue.

    Think it was my 4th post in this thread where I wrote that i was going on a motorcycling holiday to the Himalayas July 2112 so that was the reason for this build as the skies will be fantastic, You can see from the video that it will be small and light but we are on Royal Enfield motorcycles so carriage is not a problem.

    Thanks again

    Ceefna



  5. #65
    Community Moderator Al_The_Man's Avatar
    Join Date
    Dec 2003
    Location
    Canada
    Posts
    24216
    Downloads
    0
    Uploads
    0

    Default

    [QUOTE=ceefna;1008016.... we are on Royal Enfield motorcycles so carriage is not a problem.

    Thanks again

    Ceefna[/QUOTE]

    I thought for the minute you were going to be riding antiques! I didn't realize Royal Enfield were still in business.
    Do they still make the square 4? Or was that Ariel?
    Make sure you post pic's or video from the trip when you get back.
    Will you be able to use the MC battery for power?
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


  6. #66
    Registered
    Join Date
    Sep 2011
    Location
    uk
    Posts
    119
    Downloads
    0
    Uploads
    0

    Default

    Yep Al they are still making them in India, under licence though. They are 500cc single cylinder with a massive 26BHP!.
    If you do a search on youtube for ABoriginal Tours and its the Himalayas tour we are doing. Don't think they will be too pleased if i start stripping there bikes down tohook up to the battery. Hopefully there will be an inverter in the support vehicle to charge the battery. Should be able to get some fantastic Milky Way pictures and will post them for sure (if the mount tracks ok!!!!)


    Ceefna



  7. #67
    Community Moderator Al_The_Man's Avatar
    Join Date
    Dec 2003
    Location
    Canada
    Posts
    24216
    Downloads
    0
    Uploads
    0

    Default

    I guess you are renting the bikes then?
    Do the Sherpa guides ride M.C.s now?
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


  8. #68
    Registered
    Join Date
    Sep 2011
    Location
    uk
    Posts
    119
    Downloads
    0
    Uploads
    0

    Default

    Yes we are renting the bikes and I think the sherpa's have helicopters these days!!!


    Ceefna



  9. #69
    Registered
    Join Date
    Oct 2005
    Location
    Australia
    Posts
    2392
    Downloads
    0
    Uploads
    0

    Default

    That Astrotrac device is very nice!
    Astrophotography Made Easy - Home

    As you suggested it does use a scissor frame and leadscrew. It also uses two microprocessors. Obviously they have solved the problem of the trigonometry processing, using the microprocessor to compensate the tangent and produce steady angular motion by varying the speed of the motor over time.

    I still really advise you change to a rotational drive system where the steady motor speed will cause steady frame rotation.



  10. #70
    Registered
    Join Date
    Sep 2011
    Location
    uk
    Posts
    119
    Downloads
    0
    Uploads
    0

    Default

    Hi, you are right the design has problems. The Astrotrac as you say must use software to compensate or when they have there custom drive rod machined they machine the rod to compensate for the error.

    Have done another poor drawing of "drive v2" please have a look:-
    http://img401.imageshack.us/img401/9...eradrivev2.jpg

    All the dimensions are the same and with a friction drive I do not have to worry about the error that gears introduce. I really do not want to use any sort of pulley/belt config as I want to keep the mowing parts down to a minimum for transportation etc.

    My version 2 design would do away with any need for a rewind as the motor could be moved away from the top arm and reset manually. The only issue I can see with this I will loose a lot of resolution i.e if I use a 4mm motor drive then my gear ratio will be 8x less than with the 0.5mm rod design. Suppose I could gear the stepper down but it would be much better to simply fasten it under the lower arm and direct drive to the top arm.

    Any thoughts on the new idea/ friction drive etc?

    Ceefna



  11. #71
    Registered
    Join Date
    Oct 2005
    Location
    Australia
    Posts
    2392
    Downloads
    0
    Uploads
    0

    Default

    It's inovative and simple for sure, that's a nice design.

    What worries me is that a telescope is a high power magnifier and even the tinyest error or jump in degrees will move the image and wreck your timelapse photography. For instance if the friction roller glitches in any way it will directly affect your angle. And friction rollers generally need a deformed rubber element (rubber tyre under compression etc) which may not translate perfectly to movement.

    Personally I would look at something like a 5" fully circular pulley on the arm, say a 0.5" pulley on the drive (giving 10:1) and say a 50:1 or 100:1 gearbox on the stepper motor. That's still quite portable.

    Or another (better) idea, use a 3" or 4" plastic gear, and a simple pinion on the stepper shaft (as a work drive).

    Hopefully others will speak up, or you might want to post in the "mechanical designs" section of the forum. There may be someone who has done a very high precision rotational drive that would be perfect for your needs.



  12. #72
    Registered
    Join Date
    Sep 2011
    Location
    uk
    Posts
    119
    Downloads
    0
    Uploads
    0

    Default

    I agree with you that a friction drive is not the best idea so have a look at Version 3!!!!!!
    http://http://img855.imageshack.us/i...95/drivev3.jpg

    The flexible plastic rack gearing would be perfect to follow the slight curve involved. I was thinking If I used 2 lengths of rack gear and a deep pinion gear then if I set the two lengths of rack gear with the teeth a fraction of a mm out of line then this would act as an anti backlash setup?
    This setup is the highest resolution design to date.

    Just like to add i really appreciate all the time you are spending helping me with my project.

    Ceefna

    Sorry, too many http://'s in that link. Try this:-
    http://img855.imageshack.us/img855/9295/drivev3.jpg

    Romanlini please don't think i am ignoring your pulley/belt ideas I would just like to make the arm design work if possible.
    Just realised that the gearhead needs to be 100/1 not 10/1, am i right?
    Another edit to the calculations in my picture. In the final pulse calculation I forgot to show my formula:-
    Sidereal seconds/gear ratio/microsteps= seconds per pulse i.e.
    86164.1/188495.5592/1200=0.00038093 seconds per pulse. Think that's right!

    Ceefna

    Last edited by ceefna; 10-18-2011 at 03:49 PM. Reason: incorrect link


  13. #73
    Registered
    Join Date
    May 2007
    Location
    US
    Posts
    781
    Downloads
    0
    Uploads
    0

    Default

    I have not read every post in the thread so.

    Have you looked at how this problem has been solved in the past?

    For portability and weight probably hard to do much better then something like this.
    Barn door tracker - Wikipedia, the free encyclopedia
    I kind of like the bend the threaded rod to deal with the tangential errors.

    More stuff
    http://ngc704.home.comcast.net/~ngc704/eq%20platform/



  14. #74
    Registered
    Join Date
    Sep 2011
    Location
    uk
    Posts
    119
    Downloads
    0
    Uploads
    0

    Default

    Thanks for the links Andre', yes I have spent hours trawling through the barn door design's and I am now tending to agree with RomanLini that a simple angular drive is going to be the way to go simply for cost/ ease of build. I spent hours last night on google pricing the parts to build the arm type and it is not going to be within my budget.

    I am going to return to my original plan of a simple eq mount(like a GEM), polar aligned and turned by a stepper through a gearbox.

    My Linistepper kit arrived today great service thanks James, so going to solder that together first job.

    Ceefna



  15. #75
    Registered
    Join Date
    Oct 2005
    Location
    Australia
    Posts
    2392
    Downloads
    0
    Uploads
    0

    Default

    I actually meant "WORM drive" not "work drive" in my last post, in case that typo confused anyone.

    Ceefna- It's cool if you want to stay with a scissor type design, it's your baby after all. I still like the idea of a worm drive, so maybe you could adapt your last "curved rack" design to use a worm pinion on the stepper motor (and mount the motor at 90') instead of a straight pinion.

    That gives 4 benefits; 1; Worm gearing is about 10 to 15 times better, so you can use a smaller motor. 2; This makes stepper motor microsteps much smaller so per-microstep errors will have much less effect on camera movement. 3; The worm pinion can be sprung against the curved rack, removing all backlash. 4; The pinion/worm will average gear mesh nonlinearities, unlike a straight pinion that usually has "cogging errors".

    If you have a CNC machine you can cut the curved rack out of flat plastic stock (a simple 2D pattern) on the CNC machine. For that matter you could cut both main scissor parts from flat plastic stock, making it lightweight and beautiful.

    Thanks too for the links Andre'B they were interesting!



  16. #76
    Registered
    Join Date
    Sep 2011
    Location
    uk
    Posts
    119
    Downloads
    0
    Uploads
    0

    Default

    I wish I had access to a CNC but unfortunatly I only have a pillar drill and a router. I cannot see any benifit in using the complicated to build arm design over a simple GEM type mount.
    I have got 2 of these steppers but can't find the specs for this custom model. Is there any way to tell? resistance across windings or another way?

    eBay - The UK's Online Marketplace
    I will use this type of gearbox:-
    Multi ratio gearbox and motor MFA
    in the 1024 to 1 config driving my 73 to 1 worm gear as a final drive.
    74752 to 1 with 1200 microsteps will provide great resolution.

    Will do another "Microsoft Paint"!!!!! picture of my idea.

    When I am putting my Linistepper together which are the 2 caps I need to change for the step smoothing? also to what value? and lastly does the xtal have a positive pin or will it fit either way? is the centre pin on the one supplied with the kit not used?

    Ceefna



  17. #77
    Registered James Newton's Avatar
    Join Date
    May 2005
    Location
    USA
    Posts
    1397
    Downloads
    0
    Uploads
    0

    Default

    Quote Originally Posted by ceefna View Post
    When I am putting my Linistepper together which are the 2 caps I need to change for the step smoothing?
    C5 and C6. Please see:
    LiniStepper, lini, stepper, linear, 6th microstep, linear microstepping stepper motor driver, constant current linear driver, circuit Linistepper boards, LiniStepper kit, hobby stepper, robot stepper driver kit, CNC stepper driver kit for further documentation.

    Quote Originally Posted by ceefna View Post
    also to what value?
    That depends entirely on your motors and how fast the driver will be moving. I would strongly recommend you build it with the supplied components first, then once it is up and running, try increasing the capacitance by adding additional capacitors in parallel and experiment with the effect.

    Quote Originally Posted by ceefna View Post
    and lastly does the xtal have a positive pin or will it fit either way? is the centre pin on the one supplied with the kit not used?
    Insert the XTAL as shown in the picture under step 2 of the assembly instructions at:
    techref.massmind.org/techref/io/stepper/linistep/LiniV2_bld.htm

    Please note the instructions as well: "Next is the 16MHz ceramic resonator (ORANGE). It is a bit tall and fragile, and is best laid down. First bend its legs GENTLY with small pliers, then insert and solder it."



  18. #78
    Registered
    Join Date
    Oct 2005
    Location
    Australia
    Posts
    2392
    Downloads
    0
    Uploads
    0

    Default

    Ceefna, that stepper motor will probably run ok from about 12v and 300mA (0.3 amps). You can also probably run it from much less current (to increase battery life) because you have a lot of gearing so motor torque is not very critical.

    I take it you are going for a design of; motor->gearbox->pulley now?


    Hi James.

    If Ceefna goes with a xtal for highest accuracy (not a resonator) he needs the xtal and two 22pF caps.



  19. #79
    Registered
    Join Date
    Sep 2011
    Location
    uk
    Posts
    119
    Downloads
    0
    Uploads
    0

    Default

    Hi guys , thanks for the info. Yesterday after having an accident with a 1mm cutoff wheel on my angle grinder! a couple of hours at the hospital and quite a few stiches later. Fortunately its my right hand and I am left handed so I am not totally out of action.

    Yes I am going for the tried and tested motor and gear design, much less engineering involved.
    I am just putting the Linnistepper together, the xtal I have got is a 20MHz HC49 which has 2 pins. What i needed to know is do these just fit into the 2 outer pcb holes?(the ceramic has 3 pins) and ignore the centre hole?/ does the xtal need a spacer under it?
    and I take it it does not have a polarity?

    Thats good that the motor will run on such low current, I think I will work out the resistors to run it at 0.2A and see how that goes. If I am running such low current will I get away with a tiny heatsink on the transistors.

    RomanLini while I am recovering from the grinder attack I will work out a last/final and never to be changed/ever pulse rate for you to work your genius on( if you would be so kind!)

    Ceefna



  20. #80
    Registered
    Join Date
    Sep 2011
    Location
    England
    Posts
    32
    Downloads
    0
    Uploads
    0

    Default

    Funnily enough I'm doing the exact same project and using a PIC 16F628A

    With the exception mine is laptop computer controlled using homemade software in visual basic.

    I've done all the leg work of programming the pic and the electronics. I just need to finish the design of the actual camera mount (Pan, Tilt, Dolly) system.

    If you have designs already made up, maybe we could save ourselves the bother by exchanging designs?

    Attached Thumbnails Attached Thumbnails Drive a 1.8 degree stepper at 1 RPM-16f628a-time-lapse-controller-pcb01-jpg   Drive a 1.8 degree stepper at 1 RPM-16f628a-time-lapse-controller-pcb03-jpg   Drive a 1.8 degree stepper at 1 RPM-dom_0005sm-jpg  


Page 4 of 11 FirstFirst 1234567 ... LastLast

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  


About CNCzone.com

    We are the largest and most active discussion forum for manufacturing industry. The site is 100% free to join and use, so join today!

Follow us on


Our Brands

Drive a 1.8 degree stepper at 1 RPM

Drive a 1.8 degree stepper at 1 RPM