Shop OBEX P1 Docs P2 Docs Learn Events
Power for Servos from SX Tech Tool Board — Parallax Forums

Power for Servos from SX Tech Tool Board

John KauffmanJohn Kauffman Posts: 653
edited 2005-05-11 14:34 in General Discussion
As you guys know, I am developing a course for kids that are comfortable with STAMP and want to try SX. The course focusses on redoing the WAM activities with SX/B. THen in a later course we will start them on Assembly Language.

I am now planning the servo sections and the question arises: WHat is the best way to power the servos when using a SX Tech Tool board? (Logic signal connection is not a problem). There is no Vin like Homework board or servo headers like BOE. They are using the Parallax wall wart of 7.5 volts, but there is no good connetion point.

The kids have bought WAM and will buy SX Tech TOol Kit for this course. I don't want to hit them with additional cost for this course.

My ideas to date:

- Solder leads to the female power jack on the board and attached leads to the servo black & red

- Power servos from a WAM board sitting nearby (servo red and black to Vin and Vss, servo white jumpers over to SX Tech Tool board)

- Power the servo from a 6 volt battery off to the side

- Find or make a Y shaped splitter (one female to two male) to attach to the wall wart male that would give·an extra output that could be hooked to the servo power lines.

- (My favorite, from the days when you had to hack a phone line in a hotel to connect a modem): Two·safety pins stuck through the insulation of each conductor in the wall wart output line and the servo red and black leads hooked into the the closure snap of the safety pin

You guys have any other suggestions (remember, no extra components beyond WAM and SX Tech Tool Kit)?

·

Comments

  • Jon WilliamsJon Williams Posts: 6,491
    edited 2005-05-05 15:17
    Since you're just experimenting, why not use the regulated supply? This will prevent a high voltage input to the SX Tech Board (say, 12 vdc) from cooking your servos. The only thing you'd need to add is an extra cap to keep servo noise from affecting your SX -- that's easy.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Jon Williams
    Applications Engineer, Parallax
    Dallas, TX· USA
  • John KauffmanJohn Kauffman Posts: 653
    edited 2005-05-05 16:48
    When you say the "regulated supply," you mean:
    - Vdd and Vss on the SX Tech Tool header socket?
    or
    - The "regulation" voltage that is coming out of the wall wart (7.5 volts) at the female power in jack?

    Also, why is "just for experimenting" an issue? Is it because:
    - We would expect short periods of time that the servo is powered by only 5 volts which is lower then servo's spec?
    - We woudl expect short periods of time and that reduces the time that the Sx Tech Tool regulator has to carry the higher current of the board + the servo?
    - Other?

    THanks.
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2005-05-05 20:12
    Yes, use Vdd and Vss from the header near the breadboard.

    Am I wrong, or aren't servos spec'd for 4.8 to 6.0 volts? Why would 5vdc be a problem? Okay, you don't get quite as much torque as at 6vdc, but the BOE-Bot is really not that heavy.

    The regulator on the SX-Tech board is fairly beefy and has a heat sink; I think it will handle the SX and a couple servos without problems.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Jon Williams
    Applications Engineer, Parallax
    Dallas, TX· USA
  • PJMontyPJMonty Posts: 983
    edited 2005-05-06 05:12
    Jon,

    I use 5V regulated for RC style servos all the time. They work great with it.
      Thanks, PeterM
  • Russ FergusonRuss Ferguson Posts: 206
    edited 2005-05-11 13:07
    Does the 'SX Tech Tool board' have any features that are not on the new Development Board?

    Would the 'Development Board' be a good substitue for the 'SX Tech Tool board' for a person that is just getting started with the SX tool kit?

    I'm I going to want to start out using the 'SX Tech Tool board' and then move to the 'Development Board' after I have the basics down?

    Russ
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2005-05-11 13:15
    The SX Tech board is a great place to start because it has a small solderless breadboard to plug components into. The "proto" boards that we're working on are reall intended for more permanent projets; they have a through-hole component area where you would solder your project components in. Our goal is to be able to offer the proto boards at a cost low enough to justify using it for one-off projects. Stay tuned.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Jon Williams
    Applications Engineer, Parallax
    Dallas, TX· USA
  • John KauffmanJohn Kauffman Posts: 653
    edited 2005-05-11 13:25
    For completeness on the forum, let me post that I found an answer in the literature:

    Servo connections to the SX Tech Tool board are covered in Daubach's 2 ed. page 427 (Application - SX on BoeBot frame)
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2005-05-11 14:34
    I've attached a template for an SX/B robot that will control two servos and two IR LEDs.· This is based on Guenther's book project.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Jon Williams
    Applications Engineer, Parallax
    Dallas, TX· USA
    sxb
    sxb
    Robot.sxb
    4K
Sign In or Register to comment.