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Servo transistor control — Parallax Forums

Servo transistor control

AndroidAndroid Posts: 82
edited 2013-09-23 07:56 in BASIC Stamp
Hi everyone i am trying to
control a continuous servo motor with a 2N3904 transistor. Not sure how to connect the servo to the transistor . Anything helps!
-Android

Comments

  • Duane DegnDuane Degn Posts: 10,588
    edited 2012-10-29 19:08
    You shouldn't need a transistor to control a servo. The Basic Stamp just sends pulses on the logic line and the servo is powered from 4.8V to 6V. Lots of Basic Stamp boards have servo connections to make this easy. The Stamp itself doesn't directly power the servo.
  • AndroidAndroid Posts: 82
    edited 2012-10-29 20:11
    I would like to use the transistor and potentimeter so that when i spin the potentimeter it increases/decreases in speed. I want to use as little programming as possible i am short on time.
  • Duane DegnDuane Degn Posts: 10,588
    edited 2012-10-29 20:51
    I'm not familiar with a technique that uses a transistor for servo control. Maybe someone else knows?

    I will probably help if you describe in more detail what you wish to accomplish. Are you using a Basic Stamp?
  • W9GFOW9GFO Posts: 4,010
    edited 2012-10-29 21:11
    The only way I have used a transistor in the control of a servo is when it is part of a 555 servo tester circuit - no microcontroller required.

    SSTschematic.jpg


    What you want to do would require very little programming if using a Basic Stamp.
    SSTschematic.jpg
    1024 x 594 - 52K
  • ercoerco Posts: 20,256
    edited 2012-10-29 23:00
    So you're using a continuous rotation servo and you want manual potentiometer speed control? If so, you can just use one of these $2 servo testers and it's all done for you. http://www.ebay.com/itm/multi-Servo-tester-3CH-ECS-speed-controler-tester-Power-CHANNELS-CCPM-meter-/280929965473?pt=US_Character_Radio_Control_Toys&hash=item4168bb15a1

    Here's how it works with a standard servo: http://www.youtube.com/watch?v=oVs00r-K53Y
  • AndroidAndroid Posts: 82
    edited 2012-10-30 16:50
    Thank you all for helping! I solved the problem, I was focusing to much on the transistor and wasn't thinking about the potentiometer.
    Once again thank you for all the help!
    -Android
  • benybeny Posts: 2
    edited 2013-09-23 07:56
    @Android this is not a big issue, a transistor can be used a switch and with faster switching you can control a servo. As suggested earlier in this post, you can control it using a 555-timer or you can just use the motor diver circuits available on the manufacturer's website. The great thing about using servos and motor controls these days is that one doesn't need to derive any driver circuits. Almost every type of driver circuit one needs is available on the internet. You can also try looking at the datasheets given with the servos which not only contain the maximum limits but also the appropriate ICs that can be used to drive them.
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