Large Brushed servo setup on the cheap (WIP) - Page 11


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Thread: Large Brushed servo setup on the cheap (WIP)

  1. #201
    Member samco's Avatar
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    The gate resistance should be calculated to work with the mosfet's input capasitence.. but I just used 10ohm. the rest are above.

    sam


    Quote Originally Posted by julius64 View Post
    Hi Sam:
    I am working in a full bridge with mosfets B25NM60N and two drivers IR2111, and I think that I have problems with my driver circuit, I dont have Resistance gate in the mosfet, and it can to be this a problem, but I see your full bridge and I want to make a similar circuit of drivers.
    I have a 3 cuestions:
    The first cuestion: In the side Gate of the mosfet, You have resistance? and if you have resistance: that is a value?
    The second cuestion: you can help me send me a schematic with the resistance and capacitor value and the position in circuit drivers??
    Very thank Sam.




  2. #202
    Member samco's Avatar
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    Very nice looking.. any update.. I know have a puma arm without controls that would be nice to have current limiting. Also - do you have the actual eagle files?

    thanks
    sam


    Quote Originally Posted by kestreltom View Post
    OK!

    I decided to photo-etch the pcb and use my Kasuga to drill the vias and holes.

    I had to expose and etch 2 boards to get it right.

    The drilling went well.

    Here is a screenshot of the drill pattern in Mastercam.



    Here is a shot of the Kasuga milling out the vias with a .025" drill. This toolpath involved 4 tool changes, and was 443 lines of G code. Whew!



    Here is a shot of pcb with a few components. The IR21844 is the small smd chip on the right.




    Tom




  3. #203
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    Red face A cuestion.

    Hi.
    I have a cuestion about same project that I asked a month ago: What is a frequency to gate of mosfet?? I am working with a frecuency PWm of 40KHz.
    Very thank.



  4. #204
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    20 Khz seems to be the most commonly used PWM frequency, I think the higher frequency rates are mainly for low inductance motor's.

    Russell.



  5. #205
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    I finally got some time to work on some of this..

    I added current limit although untested - I have to make a board next.

    http://www.electronicsam.com/images/.../newschem5.png





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    Samco: It looks very impressive. Is there any specific reason to use IR2183 instead of IR2111 as Gate Driver ?
    Cristobal



  7. #207
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    Sorry, I made a mistake writing IR2183;it should be IR2184.



  8. #208
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    mainly because it has an disable pin..

    sam



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    Hey Samco,

    Just a quick note:

    Sorry to be out of touch for the summer. I will have more time to finish my board this winter, and will post the results.
    Yes, I do have the Eagle files. I think I linked to them in a previous post, but I will check and re-post again.

    Tom



  10. #210
    Member samco's Avatar
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    Some progress. I think the board may require a few tweeks. Working so far.

    "http://au.youtube.com/watch?v=fGF07oVkl6M"]YouTube - EMC2 closed loop test with simple h-bridge and pluto-p

    "http://au.youtube.com/watch?v=eUmFKOVepYY"]YouTube - Servo h-bridge running with emc2



  11. #211
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    It's looking good - congratulations!



  12. #212
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    deleted

    Last edited by vrsculptor; 11-10-2008 at 10:15 PM.


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    Hey Samco,

    FYI, here is a link to the final Eagle files that I made. Also contained is a copy of my library file so you won't get missing symbols and defs. There are also some Adobe Illustrator files, Excellon drill files, and dxfs for the film, etc. This link will prompt you to download the 4.5 megabyte zip file.

    Hope this helps.

    Tom


    btw. When you hook up your pins to the HalScope pictured above, what pins are you using as defined in HAL, and what are you using for the trigger? I have not been able to set this up to trigger properly and see meaningful results.
    Any info here would be very helpful.



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    Default Sorry, can't fix the link!

    Hello all,
    I just got an email that the link that I posted above does not work.
    For some reason the CNC zone servers have software daemons the remove
    the underscores from the links & filenames that I have tried to post above.
    I do not have the ability to change the folder names or file names of the source files, so at this time, I cannot fix the above link.
    Sorry!
    Tom

    Last edited by kestreltom; 01-24-2009 at 12:30 AM. Reason: unable to fix file link


  15. #215
    Gold Member acondit's Avatar
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    Quote Originally Posted by kestreltom View Post
    Hello all,
    I just got an email that the link that I posted above does not work.
    For some reason the CNC zone servers have software daemons the remove
    the underscores from the links & filenames that I have tried to post above.
    I do not have the ability to change the folder names or file names of the source files, so at this time, I cannot fix the above link.
    Sorry!
    Tom
    Tom,

    I just added underscores between final and eagle and eagle and files and it worked for me. They aren't visible in the link because of the underlining.

    http://www.foxpointdesign.com/cnc_st...agle_files.zip

    Alan



  16. #216
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    mine has gone thru a few re-designs.. I think this is the final. This was the latest tests. You can hear it current-limiting on revearsals... I totally space out negative voltages across the sense resistor getting into the lm393. That put it into an unknown state. go figure . The video is after I had that revelation.. but adding the diode (schottcy) and a few bypass caps made me re-think the layout again. I wanted the mosfets to set against the back of the circuit board and isolate the isolators better. Getting there. Having fun (hope to mill the new board today)

    "http://www.youtube.com/watch?v=qY-FCN5ZXkg"]YouTube - PICT1396




    http://www.electronicsam.com/images/...wcurrentlimit/



  17. #217
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    still going to look pretty close to this..

    Attached Thumbnails Attached Thumbnails Large Brushed servo setup on the cheap (WIP)-h-bridge-jpg  


  18. #218
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    Quote Originally Posted by samco View Post
    Yes - The servo amps I have been playing with require a PWM signal for CW and a pwm signal for CCW (I call it PWM+PWM). (very simple H-bridge.) Now IIRC - the mesa card only supports PWM+DIR at the moment. Well - unless you buy the servo interface card which gives you +/-10v out. (7i33). SO if you want to do PWM+PWM - you will need a little bit of logic.

    most industrial amps use +/- 10v or pwm+dir.

    sam
    Actually up/down PWM mode is supported by HostMot2 firmware:

    output-type:2



  19. #219
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    Peter! Good to see you here. Yes - that quote is pretty old. The work on the hostmot2 firmware is awesome... hardware stepgen is also available with it. (plus it is just more flexable)

    after I get the bugs worked out with the amps - I have a nice set of 5i20 cards that will do the hard work.

    sam
    aka skunkworks on irc.

    Quote Originally Posted by PCW_MESA View Post
    Actually up/down PWM mode is supported by HostMot2 firmware:

    output-type:2




  20. #220
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    getting there...

    sam

    Attached Thumbnails Attached Thumbnails Large Brushed servo setup on the cheap (WIP)-703qofx-jpg  


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Large Brushed servo setup on the cheap (WIP)

Large Brushed servo setup on the cheap (WIP)