Controlling Pan Tilt by 3-Axis Accelerometer

[roy]

[Subject]
Controlling Pan Tilt by 3-Axis Accelerometer


[Board]
a. PHPoC Blue (P4S-342)
b. bread board extend board for PHPoC Blue



[Sensor/Module]
a. Servo Motors * 2: RB-65PG Pan Tilt Type (Up-Down, Left-Right)


b. 3 Axis Accelerometer: AM-3AXIS Ver.03


[Connection]


[Description]
1. Get acceleration values of each of 3 axis(X, Y and Z) via an accelerometer
2. Control an angle of servo motors according to extent of gradient of an accelerometer due to gravity
3. Control servo #1 by gradient of X-Z axis
4. Control servo #2 by gradient of Y-Z axis

[video]

[Source Code - task0.php]

<?php

include "/lib/sd_340.php";

$g_arr_value = array(0, 0, 0);

function init_ht($dev)
{
    $pid_ht = pid_open("/mmap/ht$dev");
    pid_ioctl($pid_ht, "set div us");
    pid_ioctl($pid_ht, "set mode output pwm");
    pid_ioctl($pid_ht, "set count 1500 20000");
    return $pid_ht;
}

// init and start servo motors
$pid_ht0 = init_ht(0);
$pid_ht1 = init_ht(1);
pid_ioctl($pid_ht0, "start");
pid_ioctl($pid_ht1, "start");

// main loop
while(1)
{
    for($i = 0; $i < 3; $i++)
    {
        // get adc input values
        adc_setup(0, $i);
        $value = ((adc_in(0) / 4095.0 * 3.3) - 1.65) / 0.66;
        if($value > 0)
        {
            if(($value < 0.1) || ($value > 1))
                $value = floor($value);
        }
        elseif($value < 0)
        {
            if(($value > -0.1) || ($value < -1))
                $value = ceil($value);
        }

        $g_arr_value[$i] = $value;

        // calculate offset
        $offset = round(($g_arr_value[$i] * 800));
        $width = 1500 + $offset;

        // control servo motors
        switch($i)
        {
        case 0:
            pid_ioctl($pid_ht0, "set count $width 20000");
            continue;
        case 1:
            pid_ioctl($pid_ht1, "set count $width 20000");
            continue;
        }
    }
}
?>