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Re: [SeattleRobotics] servos

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  • Jeff Spencer
    Here s the options I know of: 1) Replace the pot with two resistors to generate a center resistence. 2) Cut the shaft off the pot to roughly the center and
    Message 1 of 4 , Jun 30, 2000
      Here's the options I know of:
      1) Replace the pot with two resistors to generate a center resistence.
      2) Cut the shaft off the pot to roughly the center and glue it.
      3) Cut the shaft off the pot, cut a new slot, bend the pot to face sideways
      and drill a hole for screwdriver access to make it adjustable while the
      servo is assmbled (this is on the web somewhere but I don't know where).

      Options 1 and 2 require that you then adjust the pulse width until you've
      found the center pulse width. This value will be unique for every modified
      servo.

      Option 3 allows you to program your desired center pulse width then adjust
      the pot to match it.

      It looks like you've chosen the 2nd option. So now you have to
      experimentally determin the correct pulse width to represent stop between
      forward and reverse.


      ----- Original Message -----
      From: <Reconbot@...>
      To: <SeattleRobotics@egroups.com>; <oopic@egroups.com>
      Sent: Friday, June 30, 2000 10:38 PM
      Subject: [SeattleRobotics] servos


      > I just hacked my first servos and I have a few questions.
      >
      > What do i need to do to set up a servo (after all the wireing. I know you
      > need a center position and the position that you want it at but how do
      they
      > coralate? What exactly is the center position? Despite the information on
      the
      > SRS web page the info to hack the servo was for a difernt take on my
      hitech
      > servos (same model but there differnt) I kept the pot and just crasy glued
      it
      > so it wouldnt turn. How would i find out the value its at? and how do i
      use
      > all this to drive the servo?
      > This is all after the wireing so its all programing and the info I'm
      looking
      > for isnt spific to an OS (I'm useing an OOpic) but I just need to know
      these
      > simple things and what there used for.
      >
      >
      >
      > Thanks a million and my first bot is on its way.
      >
      > Francis
      >
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    • Bryan E. Daniel
      These links are about modifying a hobby servomotor to rotate 360 degrees (or more): http://www.rdrop.com/users/marvin/other/servo.txt
      Message 2 of 4 , Jul 1, 2000
      • Kevin Ross
        Steven, I guess I am not exactly sure what you are trying to accomplish. It appears that you are attempting to drive a servo motor without a CPU? Are you
        Message 3 of 4 , Aug 13 12:06 PM
          Steven,

          I guess I am not exactly sure what you are trying to accomplish. It appears
          that you are attempting to drive a servo motor without a CPU? Are you
          attempting continuous rotation or positioning?

          What format are you saving your .BMP files in? When I attempt to view them,
          they appear to be a quick time movie or something along those lines. I am
          unable to view them.

          Kevin

          ----- Original Message -----
          From: Steven Frankel <TSFrankel@...>
          To: <SeattleRobotics@egroups.com>
          Sent: Sunday, August 13, 2000 5:55 AM
          Subject: [SeattleRobotics] servos


          > Did anyone notice my servo mod idea? Check out post 1174 and tell me
          > what u think.
          >
          >
          >
          >
          > To unsubscribe from this group, send an email to:
          > SeattleRobotics-unsubscribe@egroups.com
          >
          >
          >
          >
        • Pete Miles
          I once juiced up a Futaba S-148 to 18V just to see what happens. It was fast, and had lots of torque. But only did this for only a few seconds. It didn t
          Message 4 of 4 , Sep 7, 2000
            I once juiced up a Futaba S-148 to 18V just to see what happens. It was
            fast, and had lots of torque. But only did this for only a few seconds. It
            didn't fry! Probably really lucky here.

            The primary circuit inside these servos is rates to 7.2V max.

            Just don't be surprised when they die because being overloaded too much.

            Pete Miles
            petem@...

            > ----------
            > From: Reconbot@...[SMTP:Reconbot@...]
            > Sent: Thursday, September 07, 2000 2:59 PM
            > To: seattlerobotics@egroups.com
            > Subject: [SeattleRobotics] servos
            >
            >
            > I rember a while back that someone was looking for information about
            > giving a
            > servo more power. Just now I found this off the Lynxmotion web stite.
            >
            > Servo Power Requirements:
            > Author: Jim Frye
            >
            > Have you ever wondered what the limits are to servo power? Well I have
            > been
            > doing some research in this area, and have found some interesting facts.
            > The
            > servo is rated for 4.8 to 6 volts. This is representational of 4 AA Nicad
            > b
            > atteries for 4.8 volts, or 4 AA Alkaline batteries for 6 volts. However
            > the
            > servo is an analog device, which means there is a certain amount of
            > tolerance
            > inherent to the design. A rep from Hitec has assured me that the
            > electronics don't smoke until about 12 volts is applied. I have also
            > found
            > that it is considered very common for some remote control race car folks
            > to
            > power the servo directly from the 7.2 volt sub-C battery pack used by
            > the
            > drive motor. Also the servo is quite a bit faster, which can result in
            > more
            > torque when moving an item with more mass. If anyone has any usefull
            > information on measuring rotational torque using simple cheap fixturing
            > I
            > would love to here from you. Below is a list of servo supply voltages,
            > and
            > the estimated torque values. These values are based on the assumption
            > that
            > from a given percentage of increase in voltage, approximately 68% of
            > that
            > increase will be reflected as an increase in torque. For example,
            > increasing the voltage from 4.8 vdc to 6.0 vdc is a 25% increase. So 25
            > x
            > .68 = 17%, which means the increase in torque should be 42 + 17% = 49.17
            > oz/
            > in. Of course these are just estimates based on limited technical specs
            > from
            > Hitec, your mileage may vary...
            >
            > Ratings for a Hitec HS-300 Standard Servo
            >
            > -20% of rated voltage
            > 4.8 vdc = 42 oz/in
            >
            > Rated voltage
            > 6.0 vdc = 49 oz/in
            >
            > +20% of rated voltage
            > 7.2 vdc = 55 oz/in
            >
            > +50% of rated voltage
            > 9.0 vdc = 67 oz/in
            >
            > The really great part to using the 7.2 volt sub-C packs are, there
            > availability. You can visit your local hobby shop, or mail order the packs
            > f
            > rom Lynxmotion for around $20.00, we also carry the MRC Super Brain 809
            > high
            > quality peak detection quick chargers for $46.00. You can even get the
            > quick
            > disconnect plugs to wire onto your robot. Disclaimer Use this
            > information
            > at your own risk! I have several robots using the 7.2 volt battery
            > packs,
            > including a Hexapod II with 12 Futaba 9202's. It is strong enough to do
            > a
            > one handed pushup, with no hesitation. I trust the electronics enough to
            >
            > risk $720.00 worth of servos. But don't even complain to me if you blow
            > up
            > something. ;-)
            >
            > To unsubscribe from this group, send an email to:
            > SeattleRobotics-unsubscribe@egroups.com
            >
            >
            >
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