Hello, I'm trying to power a 4 channel relay module using an external 5v power supply and it doesn't seem to work. The 5v supply is connected to the jd-vcc pin and the GND of the supply is connected to the GND pin of the module but my power supply is not supplying any power. It seems to work with the jd-vcc to vcc jumper attached but I saw that it could fry the microcontroller and its best to use a separate supply for the relay itself. Any ideas where I went wrong?
No common ground?
I saw this here ( How to properly use a relay module with JD-VCC from Arduino/Raspberry? - Electrical Engineering Stack Exchange) that no common ground is needed for total opto isolation.
Ok, fair enough.
Is the relay module compatible with 3.3V MCUs?
Oh, the forum has hidden your post... Again... does that sometimes.
What I'm thinking is... The I/o pins can only output 3.3V. To turn the relays off, they need to output 5V, because you connected to the 5V pin.
Try the 3.3V pin instead.
With that circuit, would @laplacee02 lose the benefit of the isolation their relay board provides? From what I remember of the hidden post, that seems to be important to them.
- Yes you are correct, however, the relay contacts supply the isolation from the Arduino and the output loads.
I’m not a fan of this type of relay module design.
- As suggested, 3V3 to Vcc might/might_not work, as there are two (2) LEDS in series.
Say 1.5v for the opto and 1.5v for the series LED = 3 volts
