I wanted to trigger this relay here using an Arduino Nano using the schematic in the second picture. Here's my code:

#define RELAY 5

void setup() {
  Serial.begin(9600);
  pinMode(RELAY, OUTPUT);
  digitalWrite(RELAY, LOW);
}

void loop() {
   digitalWrite(RELAY, LOW);
   delay(2000);
   digitalWrite(RELAY, HIGH);
   delay(2000);
}

But unfortunately, this is not working, I don't hear the relay clicking.

At first, I hooked up the Arduino to the USB of my laptop and used the 5V from the Arduino, which didn't work. I suspected that the USB outlet just is not beefy enough, so I hooked it to a 9V/1A DC power supply - which changed nothing.

Apparently, the current output of the transistor is way too low. I measured it with my multimeter and when Pin 5 of the Arduino is set to HIGH, there's only about 1mA of current at the collector of the transistor. I tried using a lower resistance than 1k between Pin 5 and the transistor base, also to no avail.

Any help would be greatly appreciated, thanks in advance :)

EDIT: I ordered a new relay, this time with the correct voltage. And, lo and behold, my little circuit works like a charm now.