Question

How can control dc motor speed according to colur using raspbeerry pi. Could you write code.

Answer 1

Ans: - We can control the speed of a DC motor using Raspberry Pi by PWM technique [ Pulse Width Modulation]. - PWM is a method for getting variable out of constant power source. I 0% duty cycle - analog Write(o) ort svt 1 1 1 25% duty cycle - analogwrite (64) suni 75%. duty cycle - analogWrite (191) 100% duty cycle – analog Write(255)

- There are 40 GPIO pins in Raspberry Pi. 26 pins can be programmed. - 17 GPIO pins can deliver maximum of 15 mA. And sum of urrents from all pins cannot exceed 50 mA. so, PWM generated by Respberry Pi can not be the DC motor directly. So, use NPN transistor as a switching device which drives the high power DC motor by taking PWM signal from PI. The motor is an induction and so while switching the motor, experience inductive spiking. This spiking will heat up the transistor heavily. So use diode to provide protection to transistor against inductive spiking. In order to reduce the voltage fluctuations, connect a capacitor across the power supply,

CODE - PV THON PROGRAM import RPi GPIO as 10 # Import time # calling header file which helps us use Gpio's of P1 calling time to provide delays in program do not show any warning 10. set warnings (False) # x = 0 10. set mode (10.BCM) # integer for storing the duty cycle value # We are programming the GPIO by BCM pin numbers (PIN 35 as GP1019') # initialise GPIO 13 as an output. 10. Set up (13, 10.OUT) 10. set up (19,10.IN) # intialise GPIO 19 as an input. 10. Setup ( 26, 10. IN) # initialise GP10 26 as an input. P = 10. PWM (13,100) p.start (0) # GPIO 13 as PWM output with 100 Hz frequency # generate PWM signal with 0% duty cycle # execute loop forever while 1: P.Change Duty Cycle (x) # Change duty cycle for changing Speed of motor. # if button! is pressed if (10.input (26) = = False): if (x<50): X = X+1 # increment X by one if x<50 if 7 sleep for 200 ms if button 2 is pressed # time. sleep (0.2) (10.input (19) = = False): if (x>0): X = X-1 time sleep (0.2) # sleep for 200 ms

After executing the program operate the control. We have to use 2 buttons connected to P[ :- - one for incrementing the duty cycle of PWM signal ther for and speed Of DC motor increases. e - Other and for decrementing the duty cycle of PWM signal speed of motor decreases.