Strong Servo for my bs2.. Why will some servos will work with bs2 and some will

trendtrend Posts: 112
edited 2004-10-27 - 05:24:04 in Robotics
I need a hefty torque servo for my bs2.· Something around 70-90 oz-in.· I have read that some servos work with bs2 and some don't... I was, do you'll have any experience with ones that have similiar torque and have worked with your bs2 project?

And why will some servos work with a bs2 and some will not?


Post Edited (trend) : 10/17/2004 6:45:38 PM GMT


  • aridaiosaridaios Posts: 57
    edited 2004-10-17 - 14:05:30
    there are some big servos I have used here

  • trendtrend Posts: 112
    edited 2004-10-17 - 18:45:34
    Well, I have heard of some servos just not working with the bs2.. Did yours work with the bs2?

    I purchased a GWServo S04:

    and am afraid it will not work with my bs2...

    How can I tell. Is it because some "servos are analog or digital"?

  • allanlane5allanlane5 Posts: 3,815
    edited 2004-10-18 - 19:06:25
    A Servo is driven with a 'PULSOUT' command from the BS2, which is repeated every 20 to 50 mSec.

    The 'PULSOUT' for a Futaba servo is a 1 mSec high pulse, to a 2 mSec high pulse. A 1.5 mSec high pulse should center the servo. 1 mSec will be all the way left, and 2 mSec will be all the way right. A Servo works by comparing a pulse generated by the current position of the shaft to a commanded input pulse. It then runs the motor in the proper direction to turn the shaft so the shaft-pulse equals the commanded pulse.

    As long as a servo is controlled by a 0 to 5 volt pulse repeated every so often, I see no reason why a BS2 could not control it.
    I've never heard of an 'Analog' or even a 'Digital' servo, though...
  • allanlane5allanlane5 Posts: 3,815
    edited 2004-10-18 - 19:14:09
    I've now looked at the spec on that servo. It says it uses the
    Futaba '1500 uSec Center' standard. That should work fine with your BS2,
    as that is the same as the '1.5 mSec Center' I talked about above.
    You do need to supply the servo power with a 4.8 to 6 volt supply, though.
  • trendtrend Posts: 112
    edited 2004-10-18 - 21:12:20
    I bet an analog"" servo is a "industrial size" servo (dc motor + encoder)...

    Thanks, yeah, I actually figured out my problem with my relay, it was a grounding problem.. well i shouldn't say i figured it out.. a fellow parallax forum member told me to figure out how to read this encoder..
  • rounderrounder Posts: 18
    edited 2004-10-27 - 05:24:04
    As to the question on digital vs analog servos.....

    An analog servo uses a lower frequency servo amplifier that pulses around 30 or so times a second. A digital servo pulses at many times that speed, depends on the servo but it's roughly 10x, I think. This increased frequency allows the·digital servo to update it's position at an increased rate, also gives the ability to hold the position accurately under load, and increased precision.·This of course is all·at the cost of increased power consumption, in some cases dramatic increases in power consumption.

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