Made The Trick Switch using Arduino microcontroller

Made The Trick Switch using Arduino microcontroller

Resistor-Capacitor Timing Basics
In electronics, sometimes we want to keep a device on for a certain amount of time even when an electrical switch is turned off. Ordinary pushbuttons used to turn electronic devices on and off can easily be operated by a timed delay switch. How awesome would it be to create such a device to delay turning off a simple LED? Such a gadget could be used to trick your friends, family, or even the local Makerspace when they see the LED staying on after the pushbutton has been released. With a few electronic components from the Ultimate Microcontroller Pack, you can make an LED (lightemitting diode) stay on for a few extra seconds when a pushbutton switch is turned off. Figure 1-1
shows an assembled Trick Switch. The electronic components required to build the Trick Switch are shown in the Parts List.

Parts List

  1. Arduino microcontroller
  2. SW1: mini pushbutton
  3. LED1: red LED
  4. C1: 100 uF electrolytic capacitor
  5. R1: 10K ohm resistor (brown, black, orange stripes)
  6. R2: 330 ohm resistor (orange, orange, brown stripes)
  7. Full-size clear breadboard
Figure 1-1. Trick Switch circuit built on a full-size clear breadboard (both the 100 uF electrolytic capacitor and red LED negative pins are wired to ground)
Figure 1-1. Trick Switch circuit built on a full-size clear breadboard (both the 100 uF electrolytic capacitor and red LED negative
pins are wired to ground)

You can create your own electrical circuits and test them using diagrams with an online simulator called Circuit Lab.

Let’s Build a Trick Switch

When you press the pushbutton switch on this device, the LED turns on. The capacitor will begin storing electrical energy from the +5VDC power supply circuit of the Arduino. Releasing the pushbutton switch cuts off the flow of electricity from the source, but the energy stored in the capacitor keeps the Arduino running for a few extra seconds. The Arduino keeps the LED lit until the capacitor’s stored energy is empty. You can build the Trick Switch using the electronic components from the Parts List and the Fritzing wiring diagram shown in Figure 1-2. Here are the steps required to build the electronic device:

  1. From the Ultimate Microcontroller Pack, place the required parts on your workbench or lab tabletop.
  2. Wire the electronic parts using the Fritzing wiring diagram of Figure 1-2 or the actual Trick Switch device shown in Figure 1-1.
  3. Type the Pushbutton sketch shown in Example 1-1 into the Arduino text editor.
  4. Upload the Pushbutton sketch to the Arduino.
  5. Press the mini pushbutton for a moment. The red LED turns on. After one to two minutes, the red LED will turn off.
Trick Switch Fritzing diagram
Figure 1-2. Trick Switch Fritzing diagram

If the Trick Switch device doesn’t work, check for incorrect resistor values, incorrect wiring, sketch typos, and improper orientation of polarized electronic components (the LED and capacitor).

Example: Pushbutton sketch

Pushbutton Sketch
Reads the capacitor voltage at digital pin 2 and turns on and off a light
emitting diode (LED) connected to digital pin 12.
17 Nov 2012
by Don Wilcher
// constants won't change; they're used here to
// set pin numbers:
const int buttonPin = 2; // the number of the pushbutton pin
const int ledPin = 12; // the number of the LED pin
// variables will change:
int buttonStatus = 0; // variable for reading the pushbutton status
void setup() {
// initialize the LED pin as an output:
pinMode(ledPin, OUTPUT);
// initialize the pushbutton pin as an input:
pinMode(buttonPin, INPUT);
void loop(){
// read the status of the pushbutton value:
buttonStatus = digitalRead(buttonPin);
// check if the pushbutton is pressed
// if it is, the buttonEvent is HIGH:
if (buttonStatus == HIGH) {
// turn LED on:
digitalWrite(ledPin, HIGH);
else {
// turn LED off:
digitalWrite(ledPin, LOW);

The ledPin value can be changed to 13 to operate the onboard LED.

Related Project: Trick Switch with On/Off Indicators

Book Reference: Make: Basic Arduino Projects
26 Experiments with Microcontrollers and Electronics
By: Don Wilcher

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