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Need Help With Simple Polarity Circuit

Discussion in 'General Electronics Discussion' started by Mack Mahon, May 1, 2017.

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  1. Mack Mahon

    Mack Mahon

    May 1, 2017

    Good day All... I am a New Member, I just discover this group. I am in need of some help, I have a pretty basic understanding of eletronic circuits, it was a hobby as a kid, and now I have a renewed interest, Please let me know if I am posting in the wrong area / Forum...

    I have a nice little workshop out back, that consists of a home Built CNC, a Miling Machine, A Metal Lathe and Two Laser Cutting / Engraving machines.

    MY QUESTION SITUATION:.... Recently I have started to upgrade my K-40 CHINESE LASER... I have purchased a Z-AXIS Table. The table uses a Stepper motor to raise and lower the cutting bed. As you are aware typically, a Stepper motor requires a driver / controller etc to function, however I was able to locate a very basic analog solution, that consists of a 12V ( AC ) Power supply and a Capacitor, and a switch, amazingly enough this basic analog circuit works, and will allow me to raise or lower the Cutting bed with a switch. When I first tested the circuit I use a three position toggle switch, just to make sure the circuit would serve my purposes, and it does... the problem with the toggle switch is that it creates 3 states... 1.) UP-motor turning clockwise... 2.) CENTER- Motor Vibrating ( like an electric razor)..... 3.) DOWN-Motor turning counter clockwise. Unfortunately, because of the nature of this toggle switch the circuit will always be in one of three states, with no actual off switch, I do realize that I could just wire in another switch (DPDT) or another type but there are issues in doing this. What I have decided the best option is...would be to use a Momentary Rocker Switch, that will leave the circuit unpowered when in the center / at rest position.... I purchased a switch that has polarity reversing built into the wiring, I am hoping this will do the trick, if not please feel free to suggest an alternate solution.

    THE PROBLEM:.... I have tested the circuit with the toggle switch as mentioned, and I have sat down wth pen and paper trying to figure out how to use the new reversing switch... but have not been able to figure this out... if this was a simple DC motor, it would of course be a breeze.... however in my situation, has three differences... 1.) The circuit requires a 12V AC power source ( I am using a 12V AC wallwart, works great )... 2.) The Stepper Motor has three connectors as opposed to two on a DC Motor Setup.... and 3.) The circuit uses a capacitior to make the Motor Function in the desired manner

    So what I need is to know how to wire this new switch into the circuit.... I should probably add that one of the reasons that a toggle switch is not the best choice, apart from the AC Vibration issue in the Center position, is that I need to be able to press the button and have it quickly release to position / stop the motor / Bed of the cutter very quickly and accurately, and a toggle switch, is not the fastest way for accuracy.

    The Switch I have bought and am hoping to use is -- Rocker Switch SWT-ROC-MOM-4W With Polarity reversing Circuit ON-OFF-ON Momentary Contact.... To better illustrate my current situation as well as what I am hoping to accomplish, I have included a Diagram that should help out... I

    Any and all help / advise is greatly appreciated. In my diagram in the bottom right corner is the actual Rocker Switch Connection Configuration, ( the pinout may not be accurate, but the orientation and connection aspect of it is correct, and therefore shouldn't pose an issue, if it does I can lookup the actual pinoot numbers. Thats about it, I hope I am clear enough in my request, and again, all help is greatly appreciated.

    Attached Files:

  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    Welcome to EP.
    To be honest I do not fully understand the switch with the "built-in polarity reversing circuit".
    I'd like to propose another solution instead: Use a double-pole toggle switch (DPDT) instead of the single pole switch you currently have.
    The wiring loks like this:
    The second pole serves only the purpose of interrupting the upper power supply line in the center position. In both on positions it connects to the same power output from the transformer.
    Without this connection, your motor should be rock steady in the neutral position of the switch.
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