Descriptions: 5V 4 Channel Blue Relay Module
4 Channel Relay Module board is used to interface any Microcontroller with Electrical Appliances/Loads. Can also be used in driving high power motors.4-channel relay output modules, relay output contacts 250A 10A. Input IN1, IN2, IN3, IN4, the signal line LOW effective. VCC, GND power input, can relay a separate power supply relay power input of JD-VCC.

What is a Relay?
A relay is an electrically operated switch. Many relays use an electromagnet to mechanically operate a switch, but other operating principles are also used, such as solid-state relays. Relays are used where it is necessary to control a circuit by a separate low-power signal, or where several circuits must be controlled by one signal.

Relays work on electromagnetism, When the Relay coil is energized it acts like a magnet and changes the position of a switch. The circuit which powers the coil is completely isolated from the part which switches ON/OFF, This provides electrical isolation. This is the reason we can control a relay using 5V’s from an arduino and the other end of it could be running an 220 to 240V appliance, the 240V end is completely isolated from the 5V arduino circuitry.

Overview:
Channel: 4 channel
Relay Operating Voltage: 5V
Triode drive, increasing relay coil
High impedance controller pin
Pull-down circuit for the avoidance of malfunction
Power supply indicator and Control indicator lamp
Power supply and relay instructions, lit, the disconnect is off;
The input signal, signal, common Terminal and start conducting;