Shop OBEX P1 Docs P2 Docs Learn Events
18 servo's, two PSC boards and 4 problems — Parallax Forums

18 servo's, two PSC boards and 4 problems

poernakapoernaka Posts: 7
edited 2005-04-12 12:40 in Robotics
Hello Stampers.

I have a problem with my two PSC's and 18 servo's

When i try to set all the servo's at once ( 18 times a SEROUT command for every channel). The last four servo's do not react.·The strange thing is that when I remove the first 4 lines of SEROUT command's the last four servo·also start working. It looks like I ca'nt control more than 14 servo's. Strange huh.

I don't get it.

HELP !
confused.gif


·

Comments

  • JonbJonb Posts: 146
    edited 2005-04-11 11:01
    Please post your code so we can better assist you.
    I can see a few possibilities in your code such as addressing which may be causing the problem. How many servos did you place on each PSC? Which ones are not responding?

    Also be certain you have them daisy chained and place the shunt according to the documentation.

    P.S. 18 servos! I have to know what you're up to.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔


    Post Edited (Jonb) : 4/11/2005 1:28:48 PM GMT
  • poernakapoernaka Posts: 7
    edited 2005-04-11 11:29
    Thanx for the replie.

    Oke I have 9 servo's connected to each board. all 9 servo's on the first board work, but only 5 servo's are working on the second board. If I test every servo independent with SEROUT they all work fine. If I repeat 18 times the the serout command for each channel, the last four serout's do not work.

    code:

    SEROUT .......... ' channel 0 psc 1
    SEROUT .......... ' channel 1 psc 1
    SEROUT .......... ' channel 2 psc 1
    SEROUT .......... ' channel 3 psc 1
    SEROUT .......... ' channel 4 psc 1
    SEROUT .......... ' channel 5 psc 1
    SEROUT .......... ' channel 6 psc 1
    SEROUT .......... ' channel 7 psc 1
    SEROUT .......... ' channel 8 psc 1

    SEROUT .......... ' channel 16 psc 2
    SEROUT .......... ' channel 17 psc 2
    SEROUT .......... ' channel 18 psc 2
    SEROUT .......... ' channel 19 psc 2
    SEROUT .......... ' channel 20 psc 2
    SEROUT .......... ' channel 21 psc 2
    SEROUT .......... ' channel 22 psc 2
    SEROUT .......... ' channel 23 psc 2
    SEROUT .......... ' channel 24 psc 2

    If I run the program only 0...8 and 16 .. 20 are working fine. 21,22,23,24 are not working.
    Now if I put a comment sign before serout channel 0 to 3 the other servo's (21,22,23,24) start working. But then servo channel 0 to 3 are not working (but that's logical)

    It looks like only 14 times serout is possible in a row or something like that. Do you have a suggestion.

    Bas.
  • JonbJonb Posts: 146
    edited 2005-04-11 13:03
    Can these same servos(which are not working) be made to work individually on their respective channels?

    Can the power supply provide enough current to power all these servos together?

    Doing a search for "PSC" I came across this post from a not too long ago:

    http://forums.parallax.com/showthread.php?p=530571

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔


    Post Edited (Jonb) : 4/11/2005 1:44:39 PM GMT
  • allanlane5allanlane5 Posts: 3,815
    edited 2005-04-11 14:04
    Really sounds like a power problem. If you are 'browning out' your Servo power supply -- in other words, it has enough current to drive 14 servo's at the same time, but not 15 through 18 -- then this would make sense.

    I don't know what is powering your PSC boards -- but this sounds like the problem.
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-04-11 14:17
    Hello,

    ·· Try placing a 3,300uF capacitor across the Servo power input terminals.· Be sure to check the polarity before powering anything on.· If this doesn't work, let me know and I have another idea to try.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • poernakapoernaka Posts: 7
    edited 2005-04-12 09:36
    I checked the power supply, only 800 mA for 18 servo's. Stupid. Stupid Stupid.
    I got an 3 A. power supply and now its working fine.

    Thanx a lot
  • JonbJonb Posts: 146
    edited 2005-04-12 12:38
    Good to hear that the power supply was the only issue. Stamp on soldier...

    Did you take a look at the link I posted, there are other ways to send commands to the PSC then iteratively sending serial commands and your code can be optimized using variations on that method.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
  • bishopbishop Posts: 82
    edited 2005-04-12 12:40
    18 servo's? must be a walker bot.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    **************

    daniel woolston
    Teksystems Inc.
    www.danwoolston.com
    **************
Sign In or Register to comment.