ECET 365 week 1 homework Pgs 454-455
Austin Salankey
5/3/2016
DeVry University

8.9 A stepper motor has 24 North teeth and 24 South teeth. What angle change occurs on each step? If a full step is output every 1 ms (and assuming it doesn’t slip), at what speed does the motor spin? ANSWER: 360°/(4n) =
360°/[4(24)] =
360°/96 = 3.75°
Revolutions per Second (4f/N) =
4(1000s)/(96) =
4000/96 = 41.667rps
-or-
41.667rps(60sec) = 2500rpm 8.10 Draw a figure similar to Figure 8.80 showing how half stepping works. D8.13) Design an interface for a +24 V, 500 mA geared DC motor. The time constant of the motor is 10 ms. Include software to adjust the delivered power from 0 to 100%.

Answer:

I chose the TIP120 because it can sink at least 3 X the current needed for this motor.

The base current is:

I_b=I_coil/h_fe =0.5A/1000= 0.5mA
Disired interface resistor =
R_(b )≤((V_OH- V_be ))/I_(b ) = 5KΩ

Now to make PWM 10 times faster than the 10 mS we go to 1mS; or a frequency of 1kHz

// MC912 C32 C
// 1 ms PWM on PT0 void PWM_Init (void)
{
MODRR |= 0x01; // Port T, pin 0 is connected to PWM system PWME |= 0x01; // Enable PWM Channel 0 PWMPOL |= 0x01; // PT0 High then Low PWMCLK |= 0x01: // Clock SA PWMPRCLK = (PWMPRCLK & 0xF8) | 0x04; // A = E/16 PWMSCLA |= 5; //SA = A/10, 0.25*160 = 40 us PWMPER0 = 25; // 1 ms period PWMDTY0 = 0; // Initally off
}

// Set duty cycle on PT0 output

void PWM_Duty0 (unsigned char duty)
{
PWMDTY0 = duty; // 0 to 25
}

D8.14) Design an interface for a +12 V, 500 mA bipolar stepper motor. There are 200 steps/revolution. Write the software to spin the motor at 1 rps.

Answer:

const struct