Solutions

Questions

1. Answer: They are used to display status in things like alarm control panels, keyboards, monitors, and printers.
2. Answer: Period is the time it takes for a signal to repeat.
3. Answer: Frequency is the rate at which the light blinks on/off.
4. Answer: Duty cycle is a measure of how much time a repeating signal stays on (high) durings its period.
5. Answer: The period, frequency, duty cycle, and the number of times it blinks are ways to manipulate a light blinking.

Exercises

1. Answer: Change sleep(500) to sleep(250)
2. Answer: Make the first sleep value (for pin14.write_digital(1)) higher than the second sleep value.
3. Answer: sleep values of around 5 will achieve this.
4. Answer: (0)
5. Answer: You can use this loop to measure out the number of times a light blinks.
6. Answer:   
   T = t_HIGH + t_LOW
   1 = .25 s + t_LOW
   t_LOW = .75 s
7. Answer:    
   F = 1 / T
   F = 1 / .75 s
   F = 1 ⅓ Hz
8. Answer:
   %DC = [ t_HIGH / (t_HIGH + t_LOW) ] x 100%
   = [ 500 ms / (500 ms + 500 ms) ] x 100%
    =  0.5 x 100%
    = 50%
9. Answer:     
   %DC = [ t_HIGH / (t_HIGH + t_LOW) ] x 100%
   30 = [ 300 ms / (300 ms + t_LOW) ] x 100%
   0.3 =  (300 ms / 300 ms + t_LOW)
   0.3 x (300 ms + t_LOW) = 300 ms
   90 ms + .3(t_LOW) = 300 ms
   0.3(t_LOW) = 210 ms
   t_LOW = 700 ms
   Period = t_HIGH + t_LOW = 300 ms + 700 ms = 1000 ms

Projects

1. Solution

from microbit import*
        
for n in range(0, 20):
      pin14.write_digital(1)
      sleep(750)
      pin14.write_digital(0)
      sleep(500)

2. Solution

from microbit import*

time = 1000
scale = .5

for t in range (2500,0,-100):
    
    pin14.write_digital(1)
    sleep(time)
    pin14.write_digital(0)
    sleep(time)

    if t <= 1500:
        scale = .75
    elif t > 1500:
        scale = 1
        
         time = time * scale