Page 1 of 3 123 LastLast
Results 1 to 10 of 25

Thread: Servo Power Regulating

  1. #1
    Join Date
    Feb 2009
    Location
    Waterloo, ON, Canada
    Posts
    38
    Rep Power
    39

    Arrow Servo Power Regulating

    My robot is going to have 10 standard HS422 servos and I am planning to power it with 2 Li-Po batteries which add up to 7.4V.

    I am wondering how much current will all those servos draw. That's because I would have to use a regulator to step-down the voltage to 6V for the servos and I need to know if I should have one regulator per servo or what the current limit do I need for my regulator.
    I heard that the servos can draw up to 3A each when stalling. So with 10 servos, I might have to deal with 30A??
    How do people normally deal with so many servos in one robot?


    Thanks.

  2. Re: Servo Power Regulating

    This Battery Eliminator Circuit is used a lot in the RC market. It will handle the Li-Po batteries and regulate them down to 5+ volts and 10Amps. Those servos draw 150mA with no load, about 600mA with load.

    http://www.castlecreations.com/products/ccbec.html

  3. #3
    Join Date
    Apr 2008
    Location
    Sacramento, CA, USA Area
    Posts
    5,341
    Rep Power
    181

    Re: Servo Power Regulating

    Second the ccbec! I have three and could be very happy with half a dozen more. Invaluable devices.

    Make sure you get the programmer for it if you think you may want something other than 5v at some point.
    I Void Warranties�

  4. #4
    Join Date
    Feb 2009
    Location
    Waterloo, ON, Canada
    Posts
    38
    Rep Power
    39

    Re: Servo Power Regulating

    Thank you very much.

    For that, I don't really have to follow the wiring diagram right? The user manual doesn't have much information in it. Do you have datasheet that talks about what those input and output pins are?


    It said that the non-pro one can only continuously supply 5A current at maximum. And I don't know if there would be chance that each servo draw more than 1.5A. With 10 servos, would it be safe just to use the PRO version then?

    And thanks, I would probably want to drive the servos with 6V instead of 5V. And also, I am wondering if it would be okay to put a 5V linear voltage regulator to step down from 6V supplied from the CCBEC to power my camera and scoring module? This way, there would be lower loss in energy then stepping it down directly from the li-po battery. Or is there other way to do it?

    Lastly, I have never worked with li-po battery before. Are there special things that I should aware of when using li-po battery? I do know that I would need a special charger to charge it. And do I need voltage balancing for two cells (7.4V)?

  5. #5
    Join Date
    Apr 2008
    Location
    Sacramento, CA, USA Area
    Posts
    5,341
    Rep Power
    181

    Re: Servo Power Regulating

    Linear regulators have a drop-out - a certain amount of voltage that gets lost in the process. It's tough to find even a LDO (Low Drop Out) that could provide enough amperage for a wifi camera and xbees with a 6v input for 5v output.

    You'll probably want to put your regulator as a second input from your battery. Choose at LEAST 2A, 3A preferable.

    There would absolutely not be a lower loss. There is loss in every conversion in physics. Converting something converted is lossier than just converting it, in general (with exceptions, for example, a regulator that was close to its input limit and so bleeding substantial heat)

    The ccbec would also be driven at least a couple amps closer to its limit which would be unwise.

    You need to monitor the output from the battery and make sure it doesn't fall below its minimum voltage per-cell during use. Failure to observe that can lead to catastrophic (but exciting) failures.
    I Void Warranties�

  6. #6
    Join Date
    Jul 2008
    Location
    Belgium
    Posts
    633
    Images
    2
    Rep Power
    66

    Re: Servo Power Regulating

    Or, you could just hook 2 high-power diodes in series, getting a voltage drop of ~1.4v.. but then it's not regulated, so the voltage will be dependent on both current draw and battery capacity.
    Artificial Intelligence is no match for Natural Stupidity

    "For a list of all the ways technology has failed to improve life, press three" - Alice Kahn

    Resistance is futile! (if < 1)

  7. #7
    Join Date
    Apr 2008
    Location
    Sacramento, CA, USA Area
    Posts
    5,341
    Rep Power
    181

    Re: Servo Power Regulating

    Yeah, I'd definitely want to regulate the power going into the camera. The Trendnet, for example, has a regulator in the camera, but it's touchy as all get-out - hence the reason it's using a regulated wallwort instead of an unregulated wallwort. Generally, if the device comes with a [more expensive] regulated power supply it's a good idea to feed it regulated power unless you really understand what's going on inside the black-box. That's my take on it anyway.
    I Void Warranties�

  8. #8
    Join Date
    Jul 2008
    Location
    Belgium
    Posts
    633
    Images
    2
    Rep Power
    66

    Re: Servo Power Regulating

    Completely read over the entire camera part. I was under the impression it was only relating to servo power supply.

    Please ignore my previous post
    Artificial Intelligence is no match for Natural Stupidity

    "For a list of all the ways technology has failed to improve life, press three" - Alice Kahn

    Resistance is futile! (if < 1)

  9. #9
    Join Date
    Feb 2009
    Location
    Waterloo, ON, Canada
    Posts
    38
    Rep Power
    39

    Re: Servo Power Regulating

    Thanks!
    And, I was thinking that unregulated power might be better for servos since I don't really need a precise voltage level and this way can eliminate the need of one high-current voltage regulator.

    So at this point, my battery (2 cells 7.4 Li-po) will be powering 1 TrendNet IP camera (2.5A, 5V), 10 HS-422 servos (600mA, 6V), dsPIC33F (3.3V), and a 6V motor for electric airsoft gun.

    Those could add up to about 10A. After checking the max current level for the Li-Po battery that I has in mind, it only supports up to 2A max. Are there high current Li-Po battery or I just have to connect 5 batteries pack in parallel?!!

    And also, according to Castle Creation, I couldn't connect more than one of its switching regulator in parallel. So I would probably have to use one regulator for all the servos, and some how use linear regulator for all the other things including camera? Or do you think that I would be better off leaving the servo unregulated using two high power diode and regulate the camera with the swtiching regulator and other with linear regulator. (Is it really true that I can't have more than one switching regulator without major noise?)

    This is so much more complicated than I anticipated!!


    Thank you very much for your help!!

  10. #10
    Join Date
    Feb 2009
    Location
    Waterloo, ON, Canada
    Posts
    38
    Rep Power
    39

    Re: Servo Power Regulating

    I actually figure that I have to use higher power battery now...
    But I still don't know the second part of my questions..

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Question(s) 4-Motor Servo Kit Power Supply
    By patatoeswizard in forum Power
    Replies: 4
    Last Post: 02-18-2009, 03:04 PM
  2. Contest Entry Roving Servo Bot
    By Pinter75 in forum Project Showcase
    Replies: 13
    Last Post: 02-02-2009, 08:08 PM
  3. RC & Serial Servo Controller Kit
    By Al1970 in forum Garage Sale
    Replies: 0
    Last Post: 01-10-2009, 01:39 AM
  4. Question(s) Phidgets and servo voltage
    By Eric in forum Arbotix, Microcontrollers, Arduino
    Replies: 5
    Last Post: 05-12-2008, 09:32 AM
  5. Kondo web page translated.
    By Droid Works in forum Humanoids, Walkers & Crawlers
    Replies: 4
    Last Post: 10-06-2007, 06:49 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •