Resistor needed for: Arduino Micro + 12V Pump + HF3FA/005-ZTF relay

Question

I am using an Arduino Micro to turn On/Off a 12 V Water Pump. I am using a HF3FA/005-ZTF relay --> Link

Here's how I connected everything:

I control it with this code:

const int GO = 12;
void setup() {
pinMode(GO,OUTPUT);
}
void loop() {
digitalWrite(GO,HIGH); //WaterPumpON --> ON
delay(60000);
digitalWrite(GO,LOW); //WaterPumpOFF --> OFF
delay(60000);
}

Everything is working as it is supposed to:

QUESTION: Since I'm new electronics I would like to know if I need any kind of resistor somewhere within that circuit? I did not find similar circuits while googling and the only useful info was in this video: YouTubeLink_german and he does not use any resistors but he uses a different relay.

Answer 1

The relay you are using requires a coil voltage of 5 volts. Assuming that your Arduino Micro is able to supply the 5 volts at 72 milliAmps, then no resistor is needed.

Normally a resistor is used when the driving voltage is greater than the coil voltage. The resistor then "drops" the extra voltage across it so that the coil receives the correct voltage. So in the case of your relay, if you were using this relay but wanting to drive the coil with a 12 volt source, you would place a ~100 ohm, 1 watt resistor in series with it (7 volts / 72 mA).

^{simulate this circuit – Schematic created using CircuitLab}

Answer 2

DC Current per I/O Pin 20 mA source: https://www.arduino.cc/en/pmwiki.php?n=Main/arduinoBoardMicro