Using the Mini SSC II with Hacked Hitec servos.

edited 2005-06-19 - 13:02:41 in Robotics
Hello All,

I have been researching the use of the Scott Edwards Mini SSC II servo controller for a robotics project.
The information on the net that I have found is very limited in regards to using the Mini SSC II to control
hacked Hitec servos. The servos I am using are Hitec HS-805BB modified for full rotation. The pots have
been left intact with the center position set for 750 (off). Has anyone had any luck using hacked servos
with the Mini SSC II servo controller? I really want to use it as a co-processor to off load the burden to
the Basic Stamp II that I am using. Or should I perhaps look at using serin and a second BS II to do the
same thing? Any recommendations are greatly appreciated!!

Thank you!
Michael G. Jessat


  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-06-18 - 23:36:59

    ·· I'm not sure where you are having a problem using the SSC.· You would control the hacked servos exactly the same as un-modified servos.· The difference is that positions off from center (750) in either direction will cause the servo to continuously rotate in that direction until changed.· To a limited degree, the difference from center (750) in either direction will determine the speed, although once you get a certain point from it, there's no real speed change.

    Chris Savage
    Parallax Tech Support
  • edited 2005-06-19 - 00:07:09

    Thanks for your response, I really appreciate it! I guess I should have been a little clearer on my
    question. I have followed the BOE BOT manual like a bible tongue.gif I like the fact that the BS-II can
    slowly increase/decrease the pulses to the servos to attain a form of speed control. All the data
    I could find regarding the Mini SSC II related to mostly using it to control pan and tilt, along with
    robotic arm/leg uses. No real mention as to the fact if it can be used to control modified servos.
    You did provide me with the answer, that it can be in fact used with modified servos, thanks! I
    do have one more question. What you said in your reply sounds like I may not be able to get
    too much in the form of speed control using the Mini SSC II. Will these servos just move from
    dead-stop to full-throttle with nothing in between? If that is the case then, will using a second
    BS-II as the co-processor be the better alternative? I have over $300.00 worth of the little
    darlings just laying around my workshop, itching to be used yeah.gif. I guess I'm looking for
    what amounts to the best choice between the two devices. I have failed miserably in the past
    with hardware selection. I want this project to shine!

    Again, thanks for you reply!!!

    Michael G. Jessat
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-06-19 - 01:20:40

    ·· If I misled you, I apologize...The SSC would be capable of the same degree of speed control as the Stamp.· The servo would get the same information regardless of which device is controlling it.· The difference, of course, is that the SSC (Or even our own PSC) will keep the servos refreshed (Updated) while your program continues to do other things.

    ·· So, yes, you do have speed control in between stop and full speed.· What I meant was, as with any modified servo, that control is somewhat limited compared to other drive systems, due to the fact that a servo was never designed to function in that way.· It has been hacked.

    Chris Savage
    Parallax Tech Support
  • edited 2005-06-19 - 01:44:25

    Thanks a bunch! You made my day. I can finally unpack the Mini SSC II and give it a go.
    I'll let you know how I make out. Again Thanks!!!!!

    Michael G. Jessat
  • Rick KRick K Posts: 18
    edited 2005-06-19 - 06:31:18
    This may be a small point, particularly in continuous rotation applications, but there are some differences between speed control between the Mini-SSC and Parallax Serial Servo Controller and Stamp.

    The Mini-SSC speed is set as a parameter that has values between 1-255 that correspond to different pulsewidths.

    The Parallax Servo Controller uses values that correspond to 2uS pulsewidth changes, same as the Stamp, so there are 1000 steps in the range from 250-1250 (500-2500 uS)

    For continuous rotation, I doubt you'd have issues being restricted to the 254 steps in pulsewidth/speed changes, but for non-hacked servos, (arms or legged robots) this translates to .36 degrees over a 90 degree range, which can be a little choppy under some circumstances.

    Hopefully, this is helpful. Good luck.
  • edited 2005-06-19 - 13:02:41

    Thanks for the reply. I'm going to give the Mini SSC II a shot today to see how well it performs.
    I have a good feeling about it after having gotten so much feedback concerning its use with
    modified servos.

    Thanks again!

    Michael G. Jessat
  • meenmeen Posts: 2
    edited 2020-05-07 - 09:30:05
    Hey I'm new to this platform, any help is appreciated.
    I have a Scott Edwards Mini SSC II. Can I program this module using the Parallax BASIC Stamp IDE?

    Thanks in advance!
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