Resistor Flex part 2

How to use computers to build devices!

Gaelen Guzman

2025-03-25

Today:

• Review what we talked about last time
• Talk about this mushroom lamp!
• Use a computer to control a circuit
• Brainstorm cool projects!

Quick review

What makes an electric circuit?

• Voltage → Volts (V)

• Current → Amps (A)

• Resistance → Ohms (Ω)

Types of components!

• Types we talked about last time:
  • LEDs
  • Resistors
  • Buttons
  • Light-dependent resistors
  • Transistors

• Types we didn’t experiment with last time:
  • Capacitors
  • Inductors
  • Level shifters
  • Many, many types of sensors

Breadboards make testing complicated circuits easy!

Transistors: Electrical switches

OFF if no current delivered to the Base

ON when even a tiny bit of current flows to the Base

Assemble a night light

Hands on challenge: Night light

Components:

• Breadboard
• 5 V power supply →
• LED →
• 220 Ω Resistor →
• 100 kΩ Resistor →
• LDR →
• Transistor →
• Jumper cables

Let’s talk about inventing!

My mushroom lamp (& making your own!)

The main components of the mushroom lamp

1. A piece of bark

2. Silicone sealant

3. Red-Green-Blue LEDs

4. An ESP-32 microcontroller (a small computer)

5. A level shifter and some resistors to control the LEDs

You can use a computer to control a circuit

Example 1: A blinking LED

// Tell the computer where the LED is
#define LED_PIN 4 // The LED is on pin "5"

// the setup function runs once when you press reset or power the board
void setup() {
  // initialize digital pin LED_BUILTIN as an output.
  pinMode(LED_PIN, OUTPUT);

}

// the loop function runs over and over again forever
void loop() {
  digitalWrite(LED_PIN, HIGH);  // turn the LED on (voltage HIGH)
  delay(1000);                  // wait for 1 second
  digitalWrite(LED_PIN, LOW);   // turn the LED off (voltage LOW)
  delay(1000);                  // wait for 1 second
}

Example 2: Use a button to control an LED

// Tell the computer where the button and the LED are.
#define BUTTON_PIN 0  // The button is on pin "0"
#define LED_PIN 4     // The LED is on pin "5"

// Setup runs when the computer turns on
void setup() {

  // Tell the computer what to do with the button and LED
  pinMode(BUTTON_PIN, INPUT);  // Button with pull-up
  pinMode(LED_PIN, OUTPUT);    // LED for feedback

  digitalWrite(LED_PIN, LOW);  // Start with LED off

}

// the loop function runs over and over again forever
void loop() {

  // If the Button is pressed, turn LED on
  if (digitalRead(BUTTON_PIN) == HIGH) {  
    digitalWrite(LED_PIN, HIGH);   // Turn LED on
  }
  // If the Button is NOT pressed, turn LED off
  if (digitalRead(BUTTON_PIN) == LOW) {
    digitalWrite(LED_PIN, LOW);     // Turn LED off
  }

}

Example 3: Use a potentiometer to control an LED’s brightness

#include <Arduino.h>

// Tell the computer where the potentiometer and LED are
#define Potentiometer_Pin 3 // The potentiometer is on pin "3"
#define LED_PIN 4 // The LED is on pin "5"

// Some information to help the computer make the LED's brightness adjustable 
const int LEDC_CHANNEL = 0;     // Use PWM channel 0
const int LEDC_TIMER_BIT = 8;   // 8-bit resolution (0-255)
const int LEDC_BASE_FREQ = 5000; // 5 kHz frequency

// Run the startup instructions for the computer
void setup() {

  // Tell the computer what to do with the LED
  ledcSetup(LEDC_CHANNEL, LEDC_BASE_FREQ, LEDC_TIMER_BIT);
  ledcAttachPin(LED_PIN, LEDC_CHANNEL);

  // Apply a brightness of "0" to the LED to start
  ledcWrite(LEDC_CHANNEL, 0);  // Apply PWM value to LED strand

}

// Instructions to repeat over and over
void loop() {

  // read the value from the potentiometer:
  int potValue = analogRead(Potentiometer_Pin); // Read the potentiometer value, save it

  int LEDbrightness = map(abs(potValue), 0, 4095, 0, 255); // Convert the potentiometer value to a brightness

  // Turn on the LED at the calculated brightness level 
  ledcWrite(LEDC_CHANNEL, LEDbrightness); 

}