5 Pin Relay

Hi all, i´m trying to make a switch for current voltage with a relay.
For first, i was doing it to switch on a LED (better to start with the basics) I bought 2 relays, one 5V and other 12V to test them.
All the references I saw on the internet, forums, fritzing and everywhere, those relays are different from mine, in pin numbers and position, so really I dont figure how to wire it; these have 5 pins

I was following this simple tutorial (in spanish, sorry, but the diagrams are clear to understand, it was the easyest I found, in the fritzing image i think he is missing the 5v wire from the breadboard) :

Any relay expert who can help me? I think I burned the 5V one already, so I want to test the other one properly
Thank you¡ :slight_smile:


That website is nonsense...

You must use a transistor (or MOSFET) to switch a relay, and you must have a free=wheel diode
to prevent the inductive kickback from destroying your transistor and Arduino.

The Arduino playground explains how to do this.

The diagram you post shows how the relay is wired internally, but you can always check with a

I cannot quite imagine how you could "burn" a relay - at least with Arduino-style voltages. You really should however, explain what sort of LED you are working with.

Damaging the Arduino is more of a concern.

Your diagram probably matches the connections of your relays, but is not entirely conclusive. use your multimeter on the "ohms" range to measure the resistance across the coil terminals - if it is less than 330 ohms, it is not suitable for direct drive from the Arduino (nor of course is the 12V one). The meter will also tell you which two contacts are normally closed. Connecting your 5V or 12V to the coil will then allow you to determine which are normally open.

Do you not have a multimeter? If not, that is your most important immediate acquisition. You can use a LED and a 330 ohm resistor to "suss out" the coil and the NC contacts.

Hi Martin,

first try to understand how a relay works, that way you could figure out the pins youself:

Do you have a multimeter?

The relay works this way:

  1. Pin 11 and 12 are “normally closed”, current will flow between them. Pin 11 and 14 are “normally open”.
  2. Apply a voltage (5 or 12 volts, depending on the relay type) to pin A1 and A2 to make the relay “switch”
  3. When the relay switches, it opens the connection between 11 and 12 and closes the connection between 11 and 14.