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Servo question — Parallax Forums

Servo question

stevertrstevertr Posts: 14
edited 2010-06-01 18:06 in BASIC Stamp
Hi all,

I need to order a few small servo's for our project, but they will be operating at very low temperatures. (-40F)
The ones on the parallax site seem to not be rated for cold temps. Can anyone recommend one that would work and would just plug right into my BS2 chip.

Regards

Steve

Comments

  • hover1hover1 Posts: 1,929
    edited 2010-05-26 21:43
    Most Hitech and Futaba, (and others) servos will work down to -20C (-4F). -40F/C is going to a specialized item. Maybe try and search for a Mil Spec servo?

    Jim
  • Peter KG6LSEPeter KG6LSE Posts: 1,383
    edited 2010-05-26 21:50
    the Berings( and Lube's ) are what I suspect are the most sensitive to cold .

    Peter KG6LSE

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    "Carpe Ducktum" "seize the tape!!"
    peterthethinker.com/tesla/Venom/Venom.html
    Never underestimate the bandwidth of a station wagon full of tapes hurtling down the highway. —Tanenbaum, Andrew S.
    LOL
  • hover1hover1 Posts: 1,929
    edited 2010-05-26 22:02
    Something is not right. If you pick a Titanium gear servo on Servo City:

    ·http://www.servocity.com/html/hsr-5990tg_servo.html

    They claim : Operating Temperature Range: -20 to +60 Degree C (-68F to +140F).

    Not the same numbers after conversion.

    Manufacture site does not spec Temp range. Strange.

    Jim
  • ercoerco Posts: 20,257
    edited 2010-05-27 20:36
    Are you building a deep-water robot to cap the BP oil spill? I know it's cold down there! Godspeed!

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    ·"If you build it, they will come."
  • Steph LindsaySteph Lindsay Posts: 767
    edited 2010-05-27 21:33
    Will the servos be exposed to the elements, or working in an enclosure? If they are working in an·insulated enclosure there will be some heat generated by the operating electronics.
  • hover1hover1 Posts: 1,929
    edited 2010-05-27 21:34
    It's only 40F down there at 5000 ft. I have never dove more than 150 feet, but you could feel the temperature drop.

    The servo should not have a problem with temp, but I don't know if they would warranty it a 3000+ PSI.

    Jim
    erco said...
    Are you building a deep-water robot to cap the BP oil spill? I know it's cold down there! Godspeed!

  • Steph LindsaySteph Lindsay Posts: 767
    edited 2010-05-27 23:22
    hover1 said...

    It's only 40F down there at 5000 ft. I have never dove more than 150 feet, but you could feel the temperature drop.

    The servo should not have a problem with temp, but I don't know if they would warranty it a 3000+ PSI.

    Jim
    erco said...
    Are you building a deep-water robot to cap the BP oil spill? I know it's cold down there! Godspeed!

    I'm guessing the servos will be going up, not down!

    http://forums.parallax.com/showthread.php?p=908604
  • stevertrstevertr Posts: 14
    edited 2010-05-29 00:50
    Still servo searching... I tried those two manufacturers (thanks for that referral by the way), and the temp ratings will work fine, but now I'm having an issue with the rotation. I need a micro servo that can rotate 120 clockwise from rest, and then 120 degrees counter clockwise from rest (without me having to take them apart and modify them since I'm barely smart enough to do this much).

    Also, while the servo is at rest, I just want to make sure it's not drawing current because I don't want to burn up all my battery power in my board just to flick a servo for half a second (twice).

    Any ideas welcome o course...

    Steve
  • hover1hover1 Posts: 1,929
    edited 2010-05-29 01:22
    Most servos will max out at +/- 90 degree. You could look at some gear driven that will do 360 degree, (and leave you some room):

    ·http://servocity.com/html/spg425a-360_360o_rotation.html

    is just one example I found quickly. There may be others.

    At rest, you can just stop sending signal to the servo. No power is used. If the servo is under physical load with no power, it will tend to migrate to the pulling load, that is to say, it will not hold a load in position if there is no signal applied.

    Jim
  • stevertrstevertr Posts: 14
    edited 2010-05-29 22:45
    Looks like we'll just use some servo linkage to make it work at 90 degrees to allow a wider servo selection.
    Question, I'm thinking of this servo. http://www.servocity.com/html/hs-82mg_servo.html
    It indicates things about RC controllers etc...in terms of mking it work. Obviously, we're using a BS2.
    Will the servo pin have enough to send a 2400Us pulse? Does it go both ways?

    In other words, can we send a 600um pulse at time X to rotate it 90 degrees counter clockwise, and then later at time Y send a 2400um pulse to rotate it 90 degrees clockwise?

    Steve
  • W9GFOW9GFO Posts: 4,010
    edited 2010-05-29 23:29
    stevertr said...
    In other words, can we send a 600um pulse at time X to rotate it 90 degrees counter clockwise, and then later at time Y send a 2400um pulse to rotate it 90 degrees clockwise?

    You can easily send a 600uS (PULSOUT 300) or 2,400uS (PULSOUT 1200) pulse with the BS2. You will need to repeatedly send the pulse every 20 mS until the servo has completed its movement though.

    Rich H

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    The Simple Servo Tester, a kit from Gadget Gangster.
  • stevertrstevertr Posts: 14
    edited 2010-05-29 23:36
    Really??? You cant just send the pulse once and have the servo move all the way?? The servo says that it turns at a rate of 60 degrees in 0.1 secs. I can't imagine it would take long to move 90 secs.

    Also, just because I'm an idiot, why is PULSOUT half the number of microsecs you want?
  • W9GFOW9GFO Posts: 4,010
    edited 2010-05-30 00:36
    No, the servo will stop moving if it does not receive a pulse. If you were to send it just one pulse it would only twitch. It wouldn't take long to move 90 degrees but you won't know how long until you try it. The load on the servo will affect it's speed. At the minimum it will take .15 sec which is at least 7 pulses. It's not a big deal though just do something like this;

    FOR i = 1 to 10
    PULSOUT 12, 300
    i = i + 1
    Pause 18
    NEXT

    The BS2 PULSOUT command works in units of 2 uS each.

    Rich H

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    The Simple Servo Tester, a kit from Gadget Gangster.
  • stevertrstevertr Posts: 14
    edited 2010-05-30 00:38
    Thanks.... Sorry to be such a clueless newbie. I'm really an expert at so many things...this just isn't one of them smile.gif
  • stevertrstevertr Posts: 14
    edited 2010-05-30 00:41
    By the way...as long as I'm not being embarrassed about being clueless....what is the english definition of those terms?

    FOR i = 1 to 10
    PULSOUT 12, 300
    i = i + 1
    Pause 18
    NEXT


    Very excited...my first BS2 starter kit arrives on Tuesday.
    I'm sure that after a few days of learning how to get an LED to blink on and off I'll be ready to program the next lunar lander smile.gif
  • W9GFOW9GFO Posts: 4,010
    edited 2010-05-30 01:17
    stevertr said...
    By the way...as long as I'm not being embarrassed about being clueless....what is the english definition of those terms?

    FOR i = 1 to 10
    PULSOUT 12, 300
    i = i + 1
    Pause 18
    NEXT


    Very excited...my first BS2 starter kit arrives on Tuesday.
    I'm sure that after a few days of learning how to get an LED to blink on and off I'll be ready to program the next lunar lander smile.gif

    It's a type of loop that only executes a certain number of times.

    Take a look at What's a Microcontroller? page 43.

    Rich H

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    The Simple Servo Tester, a kit from Gadget Gangster.
  • hover1hover1 Posts: 1,929
    edited 2010-05-30 01:22
    FOR i = 1 to 10···· Do this 10 times when you reach Next
    PUKSOUT 12, 300· Pulse Pin 12 at 300*2us (for BS2)
    i = i + 1·············· Increment i
    Pause 18·············Pause for 18 milliseconds
    Next·················· Go back to FOR instruction until it counts to 10
    Download the Basic Stamp·Windows Editor (IDE)·at:
    http://www.parallax.com/tabid/441/Default.aspx
    In the help menu, you have access to the Basic Stamp Manual and What's a Microcontroller manual. You should spend some time reading these before your hardware arrives.
    Have Fun!
    Jim
    stevertr said...
    By the way...as long as I'm not being embarrassed about being clueless....what is the english definition of those terms?

    FOR i = 1 to 10
    PULSOUT 12, 300
    i = i + 1
    Pause 18
    NEXT


    Very excited...my first BS2 starter kit arrives on Tuesday.
    I'm sure that after a few days of learning how to get an LED to blink on and off I'll be ready to program the next lunar lander smile.gif
  • stevertrstevertr Posts: 14
    edited 2010-05-30 02:51
    OUTSTANDING!!! Thanks so much!!

    It the Basic Stamp editor for Mac reliable at all?
  • Steph LindsaySteph Lindsay Posts: 767
    edited 2010-06-01 18:06
    The BASIC Stamp Editor for Mac is not made by Parallax, but it is·reliable. I believe it does not support one PBASIC command, DEBUGIN. If you use the Mac editor you will likely need specific FTDI drivers· - click the Info button next to the Mac editor software download to get the full details.

    The books mentioned by a previous poster are part of the Help file of the Windows version only, but they are also available as separate pdf downloads. For "What's a Microcontroller?" go to www.parallax.com/go/WAM·and look under Downloads & Resources. For the·BASIC Stamp Sytnax & Reference Manual, click the "BASIC Stamp Documentation" button at www.parallax.com/downloads, and you will find that title in the 5th row of the first table.

    -Steph
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