Robotic arm using raspberry pi 4

[C3sarC]

Hey guys,

My name is Cesar Chavez I am a student at Bakersfield College. I am in my last year of the program (Industrial Automation) and I was assigned to a very cool project. Basically, programming a tank robot that has a arm built on arm. I was able to program the robot to move in all directions using bluedot library and I found a simple code for the arm. The problem I have is that the arm is not functioning properly. It uses servo motors with 3 wires (brown orange and yellow) powered by raspberry pi 4. It has an elbow, wrist, and gripper. The issue, when the function for the elbow sleeps for 2 seconds, the servo de-energizes and the elbow goes down. It wont hold its position. The same thing happens with the wrist. When the function for the wrist is over and sleeps for 2 seconds the wrist goes down and doesn't hold its position. I super new to python and coding so I have tried a few things like removing sleeping time but it didn't work, I tried adding GPIO.output(11, True) right after sleep(2) but it doesn't work. Any help would be much appreciated. This is the code I have for the arm:

import RPi.GPIO as GPIO
from time import sleeppython


#funtion to control elbow
def SetElbowAngle(angle):
        GPIO.setmode(GPIO.BOARD)
        GPIO.setup(11,GPIO.OUT)
        pwm=GPIO.PWM(11,50)
        pwm.start(0)
        
        duty = angle / 18 + 2
        
        GPIO.output(11, True)
        pwm.ChangeDutyCycle(duty)
        sleep(2)
        GPIO.output(11, True)
        pwm.ChangeDutyCycle(0)
        
def SetWristAngle(angle):
        GPIO.setmode(GPIO.BOARD)
        GPIO.setup(7,GPIO.OUT)
        pwm=GPIO.PWM(7,50)
        pwm.start(0)
        duty = angle / 18 + 2
        GPIO.output(7, True)
        pwm.ChangeDutyCycle(duty)
        sleep(2)
        GPIO.output(7, True)
        pwm.ChangeDutyCycle(0)
        
        
#funtion to control gripper
def SetGripperAngle(angle):
    GPIO.setmode(GPIO.BOARD)
    GPIO.setup(3,GPIO.OUT)
    pwm=GPIO.PWM(3,50)
    pwm.start(0)
    
    duty = angle / 18 + 2
    
    GPIO.output(3, True)
    pwm.ChangeDutyCycle(duty)
    sleep(2)
    GPIO.output(3, False)
    pwm.ChangeDutyCycle(0)
    
#move to starting position
SetElbowAngle(130)
SetWristAngle(70)
SetGripperAngle(0)

#pick the object
SetElbowAngle(110)
SetGripperAngle(0)
SetGripperAngle(130)

#move back
SetElbowAngle(150)
SetWristAngle(50)

#drop the object

SetGripperAngle(130)
SetGripperAngle(0)

pwm.stop()
GPIO.cleanup()
GPIO.setwarnings(False)

Thank you in advanced !!!

Larz60+ write Nov-12-2021, 10:07 AM:
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