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is this circuit ok? 1amp 5volt stepper robotic arm — Parallax Forums

is this circuit ok? 1amp 5volt stepper robotic arm

willy1067willy1067 Posts: 107
edited 2007-03-02 07:25 in Robotics
Just got my first Basic stamp, and trying to control a 1amp 5.1 stepmotor.
I change the transistor from page 264 on "What's a Microcontroller" with a bigger transistor.· will this circuit work?

Thanks in advanced

Fernando Gomez

Post Edited (willy1067) : 3/2/2007 6:46:52 AM GMT

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2007-03-02 05:59
    The IRF510 can certainly handle 1A of current. The diagram you posted doesn't really show the reverse EMF protection diode, but page 86 of the Industrial Control tutorial shows it (download here www.parallax.com/dl/docs/books/edu/ic.pdf).
  • willy1067willy1067 Posts: 107
    edited 2007-03-02 06:09
    Thanks Mike, I did put the diodes, I just didn't wired them right I guess.· I see that I need 4 instead of just two as my diagram.·· I will make the changes;·· I also read page 86 as you sugested and it saids (optional)· Should I add them or not?··· also.... can a 9 volt battery run the homework board and the stepper?

    Post Edited (willy1067) : 3/2/2007 6:42:19 AM GMT
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  • Mike GreenMike Green Posts: 23,101
    edited 2007-03-02 06:20
    The diodes are not optional for a solenoid or motor. When the magnetic field collapses as the transistor turns off suddenly, a high voltage can be produced that can destroy the transistor. The diode dissipates the energy in the field.

    A 9V "radio" battery doesn't have very much capacity. Fortunately, the homework board doesn't draw much current by itself. If you were to leave a couple of LEDs lit with the Stamp, you'd run down the 9V battery in a couple of hours ... and that's only tens of milliamperes. You're talking about a motor with currents on the order of an ampere (at least 100 times as much). You need a separate power supply for the motor for two reasons. 1) To supply the motor with enough current at the voltage it requires. 2) To isolate the Stamp from the electrical noise and power surges caused by rapid switching of the large amounts of current needed by the motor.

    I'm sure it's mentioned somewhere in the tutorial, but you do need a common ground connection. There are noise issues there, but that's a longer discussion.
  • willy1067willy1067 Posts: 107
    edited 2007-03-02 06:31
    I made the changes to the circuit by adding the 4 diodes, are they in the right location?·· with the issue of separating the power supplies, should I just not connect the two wires Vdd to the homework boards, but to·the second power sourse or should I just connect the homework board to a bigger power supply?

    Pasience with me, I am new at this.· I am more a mechanical person than electronics or programming, but with generous people like you I will achive the understanding necesary to complete my project.·· Thanks again.

    Fernando Gomez


    Post Edited (willy1067) : 3/2/2007 6:36:45 AM GMT
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  • Mike GreenMike Green Posts: 23,101
    edited 2007-03-02 07:25
    1) Just follow the diagram in the Industrial Control tutorial for connecting the transistor/ diode/ motor coil

    2) Best to connect the motor (transistor switch) grounds to the ground terminal of a power supply just for the motor. You'll need a power source for the homework board. Something that puts out 7-9V at anything over 100ma should be fine. Connect the ground on the homework board to the ground terminal of the motor power supply.
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