Build the Adjustable Twin LED Flasher

To make the Adjustable Twin LED Flasher, simply add a 10K ohm potentiometer to the device. The flash rate can be adjusted to make the on/off toggling slower or faster. The Fritzing diagram in Figure 4-7 along with the circuit schematic diagram shown in Figure 4-8 will allow you to build the Adjustable Twin LED Flasher. The MakerShield Adjustable Twin LED Flasher is shown in Figure 4-9 and the Adjustable Twin LED Flasher sketch is shown in Example 4-2.

Figure 4-7. Adjustable Twin LED Flasher Fritzing diagram

Figure 4-8. Adjustable Twin LED Flasher circuit schematic diagram

Example 4-2. Adjustable Twin LED Flasher sketch

/*
  Adjustable Twin LED Flasher
  Two LEDs will flash at a specified rate
  based on the 10K potentiometer setting.

  01 Jan 2013
  by Don Wilcher

 */

// Two LEDs with 330 ohm series resistors wired
// in parallel connected to pin 9.
int led = 9; // pin D9 assigned to led variable.

// A 10K potentiometer center pin wired to pin A0.
// One pin is wired to +5V with the other connected to GND.
int PotIn = A0; // pin A0 assigned to PotIn variable.

int Flash; // Flash variable to be used with "delay" instruction.

// the setup routine runs once when you press reset:
void setup() {
  // initialize the digital pin as an output:
  pinMode(led, OUTPUT);
  // initialize the analog pin as an input:
  pinMode(PotIn, INPUT);
}

// the loop routine runs over and over again forever:
void loop() {
  Flash =analogRead(PotIn);  // read 10K pot, store value in Flash variable
  digitalWrite(led, HIGH);  //  turn the LED on (HIGH voltage level = on)
  delay(Flash);            //   wait for a Flash time delay in seconds
  digitalWrite(led, LOW); //    turn the LED off by making the voltage LOW
  delay(Flash);          //     wait for a Flash time delay in seconds
}

Figure 4-9. MakerShield Adjustable Twin LED Flasher