Breadboard
	BC557 transitor
	Arduino Nano
	Green LED
	resistors: 330 ohm, 1000ohm
	Capacitor 20nf
	Breadboard jumpers

Digital out pin 2 is used to flip the switch by sending the base of the transistor alternately high and low.
Code (Same as above):

const int transistor = 2;

void setup() {
  pinMode(transistor, OUTPUT);
}

void loop() {
  digitalWrite(transistor, HIGH);
  delay(1000);
  digitalWrite(transistor, LOW);
  delay(1000);
}

Aside from the LED, an analog input pin is used to read a voltage in the load chain.

Connection:

• BC557
  • Base (B): 330 ohm, Arduino D2
  • Collector (C): Green LED, Resistor 1000 ohm, Ground/li>
  • Emitter (E): 5V
• Capacitor: BC557 Collector (C) => BC547 Emitter (E)
• Voltage read: BC557 Collector (C) => Arduino A0

Download ino (Same as above)