Kootek 2 CHANNEL RELAY 5VDC

Excellent relay, I use it with a Raspberry Pi 3 GPIO and power it with the 3.3v line. Please use Power and Signal from the same source for the relay to work as you expect it to, I use 3.3v since GPIO signals at the same voltage. The relay is activated with a LOW signal, Active Low Relay. Works perfectly fine. I use this to control a 5v DC motor and works really well. Built well. Switches really quickly, stays open as expected. Outside of the Pi, tested to be working fine with 5v, 3.3v.

Product quality is really good! One thing to note is this is mainly meant for Arduino UNO. You need 5v to trigger this Relay. Arduino gives 5v output which you can connect to IN to trigger the Relay. If you are planning to use this directly with a PIR Sensor (Motion sensor) connecting the PIR 3.3v out to this Relay IN will not work. I hacked this by connecting (soldering from back of the PC board) the PIR out directly to the Emitter leg of the Octocoupler on the Relay board. it worked well. You can also use a transistor (BC547 NPN) where you can apply the 3.3v from PIR and push 5v from source to the Relay IN.

The main advantage of this relay is isolation and reverse voltage protection diode.This module has an optoisolator and the relay works fine even on 3.3V (nodeMCU). Don't buy cheap ones especially with green PCB. I was having one with green PCB. There was no reverse protection diode nor isolator. It also stopped working after a week with load of 230V 2A.

I thought its only for hobby But i used it in my project and it works perfectly

Works as expected, it is an active low relay but is uncertain to work with 3.3v logic, in my case the left one worked but right one did not. It will work just fine with 5v logic and above as Vcc