伺服控制器PCA9685和樹莓派

Question

我嘗試學習如何使用PCA9685模塊與覆盆子PI控制舵機。我下面的教程Adafruit的供給下面的代碼：

# Simple demo of of the PCA9685 PWM servo/LED controller library. 
# This will move channel 0 from min to max position repeatedly. 
# Author: Tony DiCola 
# License: Public Domain 
from __future__ import division 
import time 

# Import the PCA9685 module. 
import Adafruit_PCA9685 


# Uncomment to enable debug output. 
#import logging 
#logging.basicConfig(level=logging.DEBUG) 

# Initialise the PCA9685 using the default address (0x40). 
pwm = Adafruit_PCA9685.PCA9685() 

# Alternatively specify a different address and/or bus: 
#pwm = Adafruit_PCA9685.PCA9685(address=0x41, busnum=2) 

# Configure min and max servo pulse lengths 
servo_min = 150 # Min pulse length out of 4096 
servo_max = 600 # Max pulse length out of 4096 

# Helper function to make setting a servo pulse width simpler. 
def set_servo_pulse(channel, pulse): 
    pulse_length = 1000000 # 1,000,000 us per second 
    pulse_length //= 60  # 60 Hz 
    print('{0}us per period'.format(pulse_length)) 
    pulse_length //= 4096  # 12 bits of resolution 
    print('{0}us per bit'.format(pulse_length)) 
    pulse *= 1000 
    pulse //= pulse_length 
    pwm.set_pwm(channel, 0, pulse) 

# Set frequency to 60hz, good for servos. 
pwm.set_pwm_freq(60) 

print('Moving servo on channel 0, press Ctrl-C to quit...') 
while True: 
    # Move servo on channel O between extremes. 
    pwm.set_pwm(0, 0, servo_min) 
    time.sleep(1) 
    pwm.set_pwm(0, 0, servo_max) 
time.sleep(1) 

一切都工作得很好，伺服正確動作 - 但是我退出程序，伺服仍在接收，迫使它到一個方向的信號。如果嘗試添加鍵盤中斷並結合break語句，但是這會導致伺服器嚴重升溫。現在我害怕破壞一些東西。所以我想知道如何在退出程序後停止信號？

Answer 1

你肯定希望有一種方法來設置爲默認狀態，如果你的程序退出。在你的情況下，KeyboardInterrupt的處理程序將是要走的路。確保在處理程序中將伺服輸出設置爲標稱值。

servo_middle_position = (servo_max - servo_min)/2 

try: 
    while True: 
     pwm.set_pwm(0, 0, servo_min) 
     time.sleep(1) 
     pwm.set_pwm(0, 0, servo_max) 
     time.sleep(1) 

except KeyboardInterrupt: 
    print "User quit! Moving servo to middle position.' 
    pwm.set_pwm(0, 0, servo_middle_position) 

我猜你可能實際上並不使用傳統的伺服其中PWM佔空比決定的位置 - 如果是這種情況，伺服將停止移動一旦達到所需的位置。您應該注意，舵機在運行時會產生一定量的熱量。