A 2-Channel Relay

Good evening everyone,

I thought it would be neat to do some investigation and research on how each part operates as it arrives in the mail. So the first item is this 2-channel 5V DC relay. You would typically use these units to power higher voltage circuits with a lower voltage. In the project, this relay will be used to open and close my garage through a NodeMCU controller.

Relays have a built-in switch essentially, when a voltage change the electromagnet is charged or not, thus causing the common terminal armature to move between NO or NC.

The Front section of the Relay focuses on connectivity to the External device. 

NC1(Normally Connected Channel 1) COM (Common Pin) NO1(Normally Open Channel 1) NC2(Normally Connected Channel 2) COM (Common Pin) NO2(Normally Open Channel 2)

If you're using a electrical outlet for example, you'd splice the positive the wire to COM and another to NO or NC. Then depending on the configuration of the relay, you would do directly to AC current or be controlled through a Microprocessor.

On the back are the connections to either the micro controller or to AC:

Right: Gnd (Ground) IN1 & IN2(input 1&2) This would go to a controlled pin on a Arduino Left: Jumper settings: JD-VCC + VCC = Power handled from external source rather than Micro Controller VCC + GND = Power handled by Micro Controller

The reason I'd be using a 2-Channel Relay, in the event of a power failure a reboot of the micro controller would typically cause the circuit to activate upon restart. By placing a jumper wire between the two common pins, this operation is prevented.

Full Disclaimer, this is my first time really delving into electronics. If you find any of my data incorrect, please inform me. I want my audience and myself educated the correct way.

Further details can be obtained from Wiki or from this Source and this great source.