Tag Archives: Potentiometer

Create a Dimmable LED with a Potentiometer on the Raspberry Pi

June 23, 2022 admin

In this video lesson, we show how to create a dimmable LED on the raspberry pi using a potentiometer. Below is the schematic of the circuit we will be using.

Then we used the following code to read values through the ADC0834 analog to digital chip, and then apply a PWM signal to control the brightness of the LED.

import RPi.GPIO as GPIO
import ADC0834
import time

GPIO.setmode(GPIO.BCM)

LEDPin=23
GPIO.setup(LEDPin,GPIO.OUT)
myPWM=GPIO.PWM(LEDPin,1000)
myPWM.start(0)
ADC0834.setup()
try:
    while True:
        analogVal=ADC0834.getResult(0)
        print('Raw= ',analogVal, 'Vol= ', analogVal/255*5)
        DC=analogVal*100/255
        myPWM.ChangeDutyCycle(DC)
        time.sleep(.2)
        
except KeyboardInterrupt:
    GPIO.cleanup()
    print('GPIO Good to Go')

import RPi.GPIO as GPIO

import ADC0834

import time

GPIO.setmode(GPIO.BCM)

LEDPin=23

GPIO.setup(LEDPin,GPIO.OUT)

myPWM=GPIO.PWM(LEDPin,1000)

myPWM.start(0)

ADC0834.setup()

try:

while True:

analogVal=ADC0834.getResult(0)

print('Raw= ',analogVal, 'Vol= ', analogVal/255*5)

DC=analogVal*100/255

myPWM.ChangeDutyCycle(DC)

time.sleep(.2)

except KeyboardInterrupt:

GPIO.cleanup()

print('GPIO Good to Go')

Arduino, Tutorial

Arduino Tutorial 33: Understanding How to Control Servos with a Joystick

October 22, 2019 admin

In this lesson we show you how to precisely control the position of two servos using a joystick. We derive the math equations which will allow you to get smooth and precise control of the servo. We also add a buzzer to the project to create an audible alarm when the button the joystick is pressed.

If you want to follow along at home, you can order the Arduino Kit we are using HERE.

Typically, the servos in electronics kits are not the best ones, but are suitable to learn with. If you want a more stable and better quality servo, this is the one I user in more of my projects: HiTEC

Below is the code we developed in this project.

#include <Servo.h>
Servo Xservo;
Servo Yservo;

int Xpin=A0;
int Ypin=A1;
int Spin=2;
int XSpin=9;
int YSpin=10;
int buzzPin=7;
int WVx;
int WVy;
int Xval;
int Yval;
int Sval;
int dt=200;
void setup() {
  // put your setup code here, to run once:
Serial.begin(9600);
pinMode(Xpin,INPUT);
pinMode(Ypin,INPUT);
pinMode(Spin,INPUT);
pinMode(XSpin,OUTPUT);
pinMode(YSpin,OUTPUT);
pinMode(buzzPin,OUTPUT);

Xservo.attach(XSpin);
Yservo.attach(YSpin);

digitalWrite(Spin,HIGH);
}

void loop() {
 Xval=analogRead(Xpin);
 WVx=(180./1023.)*Xval;
 Yval=analogRead(Ypin);
 WVy=(180./1023.)*Yval;
 Sval=digitalRead(Spin);


 Xservo.write(WVx);
 Yservo.write(WVy);

 if (Sval==0){
  digitalWrite(buzzPin, HIGH);
 }
 else {
  digitalWrite(buzzPin, LOW);
 }


 
 delay(dt);
 Serial.print("X Value = ");
 Serial.print(Xval);
 Serial.print(" Y Value = ");
 Serial.print(Yval);
 Serial.print(" Switch State is ");
 Serial.println(Sval);
}

#include <Servo.h>

Servo Xservo;

Servo Yservo;

int Xpin=A0;

int Ypin=A1;

int Spin=2;

int XSpin=9;

int YSpin=10;

int buzzPin=7;

int WVx;

int WVy;

int Xval;

int Yval;

int Sval;

int dt=200;

void setup() {

// put your setup code here, to run once:

Serial.begin(9600);

pinMode(Xpin,INPUT);

pinMode(Ypin,INPUT);

pinMode(Spin,INPUT);

pinMode(XSpin,OUTPUT);

pinMode(YSpin,OUTPUT);

pinMode(buzzPin,OUTPUT);

Xservo.attach(XSpin);

Yservo.attach(YSpin);

digitalWrite(Spin,HIGH);

}

void loop() {

Xval=analogRead(Xpin);

WVx=(180./1023.)*Xval;

Yval=analogRead(Ypin);

WVy=(180./1023.)*Yval;

Sval=digitalRead(Spin);

Xservo.write(WVx);

Yservo.write(WVy);

if (Sval==0){

digitalWrite(buzzPin, HIGH);

}

else {

digitalWrite(buzzPin, LOW);

}

delay(dt);

Serial.print("X Value = ");

Serial.print(Xval);

Serial.print(" Y Value = ");

Serial.print(Yval);

Serial.print(" Switch State is ");

Serial.println(Sval);

}

Arduino, Tutorial

Arduino Tutorial 32: Understanding and Using Joysticks in a Project

October 15, 2019 admin

In this lesson we will explain how to hook up a Joystick. The easiest way to think of a joystick is to think of it as two independent potentiometer. Moving the joystick left and right changes one potentiometer, and moving the joystick up and down changes the other potentiometer. Also, pressing the knob on the joystick will activate a simple on/off switch. In this video we show you how to hook the joystick up, and then show you code that will allow you to read from the potentiometers and the switch.

If you want to follow along at home, you can order the Arduino Kit we are using HERE.

Typically, the servos in electronics kits are not the best ones, but are suitable to learn with. Heads up that in Lesson 33 we will be using a joystick to control two servos. If you want to get ready for that lesson, go ahead and order your HiTEC Servos.

This is the code that we developed in the video above.

int Xpin=A0;
int Ypin=A1;
int Spin=2;
int Xval;
int Yval;
int Sval;
int dt=200;
void setup() {
  // put your setup code here, to run once:
Serial.begin(9600);
pinMode(Xpin,INPUT);
pinMode(Ypin,INPUT);
pinMode(Spin,INPUT);
digitalWrite(Spin,HIGH);
}

void loop() {
 Xval=analogRead(Xpin);
 Yval=analogRead(Ypin);
 Sval=digitalRead(Spin);
 delay(dt);
 Serial.print("X Value = ");
 Serial.print(Xval);
 Serial.print(" Y Value = ");
 Serial.print(Yval);
 Serial.print(" Switch State is ");
 Serial.println(Sval);
}

int Xpin=A0;

int Ypin=A1;

int Spin=2;

int Xval;

int Yval;

int Sval;

int dt=200;

void setup() {

// put your setup code here, to run once:

Serial.begin(9600);

pinMode(Xpin,INPUT);

pinMode(Ypin,INPUT);

pinMode(Spin,INPUT);

digitalWrite(Spin,HIGH);

}

void loop() {

Xval=analogRead(Xpin);

Yval=analogRead(Ypin);

Sval=digitalRead(Spin);

delay(dt);

Serial.print("X Value = ");

Serial.print(Xval);

Serial.print(" Y Value = ");

Serial.print(Yval);

Serial.print(" Switch State is ");

Serial.println(Sval);

}

Beaglevone Black Rev. C

Beaglebone Black LESSON 10: Dimable LED using Potentiometer

June 10, 2015 admin

In this lesson we will create a dimable LED. We will read an analog voltage from a potentiometer, and use that to set the brightness on an LED. In order to proceed with this lesson, you will need to connect the following circuit:

Potentiometer Reading is Used to Set LED Brightness

Note we are using P9_32 as the reference voltage on the voltage divider, we are using P9_34 as the reference ground, and we are using P9_33 as the analog sense pin. We also using P9_14 as the PWM output pin. Note the current limiting resistor in series with the LED is 330 Ohm.

The object of this circuit is to read the value of the potentiometer and then to use that to set the brightness on the LED. We know that the value we read from the potentiometer will be between 0 and 1. We know that what we can control on the PWM pin is the duty cycle of the 3.3 volt signal. We know that when the potentiometer reads 0, we want a 0% duty cycle on the PWM pin, which would have the LED off. This is our first point:

(0,0)

We also know that when we read 1 from the potentiometer, we want to apply a duty cycle of 100%, or have the LED be full bright. This is our second point:

(1,100)

If we created an equation for the line between these two points, we could calculate the duty cycle that should be applied based on the potentiometer reading. The problem with this is the way our eye perceives changes in brightness. We perceive exponential changes, so if we connected the two points with a linear relationship we would see lots of change at the low end of the scale, but as we continued to move the potentiometer, the brightness would appear to saturate. In order to have a nice smooth transition from full dim to full bright as the potentiometer is moved from left to right, we need to fit an exponential curve between the two points above. We want the LED to be off when the pot is full left, and full bright when the pot is fully to the right. We could use the following exponential equation:

Duty Cycle = C^(Analog Read) – B

This should do the trick, but we need to figure out what the constants C and B need to be. We do this by first plugging in the first point (0,0) from above:

0 = C^0 – B

Anything raised to 0 power is 1, so we have:

0= 1 – B

So B = 1. There, we have our first constant. We use this, and our second point to find C.

100 = C^1 – 1

101=C^1

C=101

Now we have everything we need to calculate the Duty Cycle from the value we read from the potentiometer. The final equation is:

Duty Cycle = 101^(Analog Read) – 1

This Chart Shows how to Map Duty Cycle onto Analog Read

Note that this relationship has the desired properties. When we read a 0 from the potentiometer, we apply a Duty Cycle of 0% to the PWM pin, and the LED is off. When we read a 1 from the potentiometer, we apply a Duty Cycle of 100% to the LED and it is full bright. The exponential shape of the curve between these two points ensures that we will perceive a smooth increase in brightness as we turn the potentiometer up. Math works! It would be very hard to do this by trial and error.

We are now ready to begin developing our code. The video lesson explains the code line-by-line, and we are using commands we learned in the last few lessons.

import Adafruit_BBIO.ADC as ADC
import Adafruit_BBIO.PWM as PWM
from time import sleep
LED="P9_14"
pot="P9_33"
ADC.setup()
PWM.start(LED,0,1000)
while(1):
        analogRead=ADC.read(pot)
        dutyCycle=(101)**analogRead -1
        print dutyCycle
        PWM.set_duty_cycle(LED,dutyCycle)
        sleep(.2)

import Adafruit_BBIO.ADC as ADC

import Adafruit_BBIO.PWM as PWM

from time import sleep

LED="P9_14"

pot="P9_33"

ADC.setup()

PWM.start(LED,0,1000)

while(1):

analogRead=ADC.read(pot)

dutyCycle=(101)**analogRead -1

print dutyCycle

PWM.set_duty_cycle(LED,dutyCycle)

sleep(.2)

The code works very well, and produces a very smooth transition from fully off to fully bright.

Technology Tutorials

Tag Archives: Potentiometer

Create a Dimmable LED with a Potentiometer on the Raspberry Pi

Arduino Tutorial 33: Understanding How to Control Servos with a Joystick

Arduino Tutorial 32: Understanding and Using Joysticks in a Project

Beaglebone Black LESSON 10: Dimable LED using Potentiometer

Making The World a Better Place One High Tech Project at a Time. Enjoy!