The relay module does not transform the 12v from the power supply to 5v.
The Pi4 does need a 5V power supply - I would buy an official one for that.
The Pi GPIO that you use to trigger the relays have a 3.3V output - some relay modules work with that, some don't. You can test that by applying 3.3V to the relay input - does it switch (click)? but note some relay modules are "active low" so you connect the trigger input to 0V then it switches.
Typically, when the relay is triggered by 5V (or 3V3 or 0V) it closes its contacts to allow current to flow in another circuit powered by a separate 12V supply.
The Pi4 does need a 5V power supply - I would buy an official one for that.
The Pi GPIO that you use to trigger the relays have a 3.3V output - some relay modules work with that, some don't. You can test that by applying 3.3V to the relay input - does it switch (click)? but note some relay modules are "active low" so you connect the trigger input to 0V then it switches.
Typically, when the relay is triggered by 5V (or 3V3 or 0V) it closes its contacts to allow current to flow in another circuit powered by a separate 12V supply.
Statistics: Posted by neilgl — Fri Mar 01, 2024 2:54 pm