Question

我尝试学习如何使用PCA9685模块来控制带有覆盆子pi的伺服器。我正在关注adafruit教程，该教程提供以下代码：

# 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)

一切运行良好，伺服正确运动 - 但是当我退出程序时，伺服仍然接收信号强制它进入一个方向。如果尝试添加一个键盘中断和一个break语句，但这会导致伺服加热严重。现在我害怕打破一些东西。所以我想知道如何在退出程序后停止信号？

Answer 1

如果您的程序退出，您肯定想要设置默认状态。在你的情况下，KeyboardInterrupt的处理程序将是你要走的路。确保在处理程序中将伺服输出设置为标称值。

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)

我猜你可能实际上并没有使用PWM占空比确定位置的传统伺服 - 如果是这种情况，伺服器一旦到达所需位置就会停止移动。你应该注意到伺服系统在运行时会产生一些热量。

带PCA9685和Raspberry Pi的伺服控制器

1 个答案: