2

I know servo :

1 ms is 0 degree
1.5 ms is 90 degree 
2 ms is 180 degree

I also know servo motor has period of 20 ms and PWM from 1-2 ms, but i totally confused how to calculate angle like 30 or 60 or any angle between 0-180 . So I want to enter angle and the angle will be converted to dutycycle. than can be used in p.ChangeDutyCycle

import time
import RPi.GPIO as gpio
gpio.setwarnings(False)
gpio.setmode(gpio.BOARD)
gpio.setup(7,gpio.OUT)
pwm = gpio.PWM(7,100)
pwm.start(2.5)
def change(k):
    pwm.ChangeDutyCycle(k)
    time.sleep(1)

try:
    while True:
        k = float(raw_input("enter angle: "))
        k = (1+(float(k)/180))/20
        change(k)
except KeyboardInterrupt:
    pwm.stop()
    gpio.cleanup()
    exit
Improve this question
1
  • As originally written the question had nothing to do with the Raspberry Pi. However subsequent edits showed the use of the Python module RPi.GPIO which only runs on the Raspberry Pi. – joan Dec 2 '14 at 10:48
4

For the Raspberry Pi Python RPi.GPIO module (which seems to use dutycycle values between 0 and 100).

dutycycle = ((angle/180.0) + 1.0) * 5.0

so angle=0 gives 1.0 * 5 (5%), angle=90 gives 1.5 * 5 (7.5%), angle=180 gives 2.0 * 5 (10%), angle=45 gives 1.25 * 5 (6.25%) etc.

The RPi.GPIO ChangeDutyCycle method is not a reliable way to control servos. It uses software timing which will cause servo glitches.

Improve this answer
9
  • its pwm not ducty cylce, need to convert it to duty cycle??, – Hackaholic Dec 1 '14 at 13:06
  • pwm = duty cycle – Werner Kvalem Vesterås Dec 1 '14 at 13:08
  • @Hackaholic I edited the calculation to give dutycycle values as I think are used by RPi.GPIO. – joan Dec 1 '14 at 13:10
  • @joan yea i am using RPi.GPIO, it totally confused me – Hackaholic Dec 1 '14 at 13:11
  • ahhh i was so stupid i was using this formula but i was multpling it wiht 100, ohhh, we dont not to multiply to 100 – Hackaholic Dec 1 '14 at 13:13

Not the answer you're looking for? Browse other questions tagged or ask your own question.