1 Channel 3V Relay High Level Driver Module Optocoupler Relay Module for ESP8266 Based Board

I needed a way to control the power on my prusa i3 mk3 printer with octoprint.Octoprint has a plugin named PSU.My octoprint is running on a PI 3B+.The relay runs on 3v.Perfect for the gpio pin on the PI.Works perfectly and I highly recommend this relay for the PI.

I bought 4 of these. ZERO of them work.Powering these with 3.3V and using a digital 3.3V output from an MCU, these relays show the LED blinking, but the relay does not switch.As others have said, these are defective. DO NOT BUY.

Super easy to use and worked great. I’ve had one in switching for a few weeks now with no problem on an RPi Zero

Took me quite a while to figure out why the relay wouldn't turn on (nor would the power LED). In the end, I found bad solder joints on the optocoupler input side (x1) and output side (x2). After remelting the joints, everything worked fine.For anyone trying to figure out what the jumpers are for... if you want to power the relay coil separately from your input signal (this is probably recommended since the relay coil draws more current than most 3v3 IOs are capable of, then remove JP1 and connect your separate 3v3 to the "relay side" of the jumper pin, then disconnect JP2 and connect your separate ground to the "relay side" of the jumper pins.

The units I received were made by the same company but had different components on them and the board design has changed slightly to accommodate them. All the components - with the exception of the jumpers, relay and screw terminals were surface mount. The trigger LED is nice and I can verify that my units worked fine @ 3.3V with the ESP32. The only reason I didn't give this 5 stars is the information regarding the jumpers is somewhat vague/unclear. I believe the jumpers can be removed if you want to run the coil on the relay from a different supply than that of the Opto Isolator. The URL printed on the PCB takes you nowhere.Relay contacts on my unit were rated for 10A @ 250VAC/30VDC.

this was just what I needed to finish a project. worked like a charm. very pleased

Perfect for a high-current output for an Arduino project

Not working at all. 3.7v on signal pin was a no go, directly hitting coil pins worked, showing something was off with the pcb. Not going to troubleshoot something that should have worked out of box. Sending it back.