Controlling the speed and direction of rotation of a large stepper using a single potentiometer

Projects Programming
5

output

 pot    526, spd      0, dly      0, dir  0 Stop
 pot    526, spd      0, dly      0, dir  0 Stop
 pot    514, spd      0, dly      0, dir  0 Stop
 pot    495, spd     -1, dly   1000, dir -1 Rev
 pot    481, spd     -1, dly   1000, dir -1 Rev
 pot    473, spd     -1, dly   1000, dir -1 Rev
 pot    494, spd     -1, dly   1000, dir -1 Rev
 pot    512, spd      0, dly      0, dir  0 Stop
 pot    531, spd      0, dly      0, dir  0 Stop
 pot    551, spd      0, dly      0, dir  0 Stop
 pot    575, spd      1, dly   1000, dir  1 For
 pot    590, spd      1, dly   1000, dir  1 For
 pot    609, spd      1, dly   1000, dir  1 For
 pot    635, spd      2, dly    500, dir  1 For
 pot    656, spd      2, dly    500, dir  1 For
 pot    680, spd      3, dly    333, dir  1 For
 pot    701, spd      3, dly    333, dir  1 For
 pot    718, spd      4, dly    250, dir  1 For
 pot    739, spd      4, dly    250, dir  1 For
 pot    749, spd      4, dly    250, dir  1 For

// speed control pot

const int PotMax = 1023;
const int SpdMax = 10;
char s [90];

// -----------------------------------------------------------------------------
void
loop ()
{
    int pot = analogRead (A0);
    int spd = map(pot, 0, PotMax, -SpdMax, SpdMax);
    int dly = spd == 0 ? 0 : 1000/abs(spd);
    int dir = spd == 0 ? 0 : (spd > 0 ? 1 : -1);

    sprintf (s, " pot %6d, spd %6d, dly %6d, dir %2d %s",
        pot, spd, dly, dir, dir == 0 ? "Stop" : (dir > 0 ? "For" : "Rev") );
    Serial.println (s);

    delay (1500);        // slow prints
}

// -----------------------------------------------------------------------------
void
setup (void)
{
    Serial.begin (9600);
}