4 Channel Relay Shield

I recently purchased a box of 4 Channel Relay Shields from China for a control project. The quality of the boards is excellent but there was no documentation supplied except for an image or two on the original web site. Below is the relay board publicity shots so you get an idea of the board. I was planning to use them to switch 24VAC coils so no high voltages would be present around the Arduino or Shield. The 24vac would then drive externally (DIN rail) mounted 240VAC contactors.


Module features are as follows:

  1. Standard for Arduino Shield interfaces and shape.
  2. Can continue to stack other for Arduino expansion board (relays use Digital output Pins 7,6,5 and 4).
  3. 3x M3 screw positioning holes for easy installation.
  4. High Drive (5V or 3.3V) normally open contact closure.
  5. Onboard relay indicator (red)

Special Note: If mounting on an Arduino Uno, verify that the pins of the green terminal blocks do not interfere with the USB interface (which is higher than normal).



The circuit diagram for the shield is pretty basic, take note that the drive signal from the CPU pin to the relay drive logic is not drawn correctly.

UT8DfacXaXeXXagOFbX2And the board layout diagram is:



Relay Shield Interface: (the last picture show)

  • Relay: sky- 5V DC relay , model HJR-4102-L-5V, which Relay1 behalf of the 1st relay , the other and so on.
  • Power Interface : 5V DC power interface
  • Indicator: four lights are red when the relay is driven high , the corresponding indicator will light up .
  • Relay Terminals: Terminal high-power , high-current high voltage can be connected to the device . The 1st foot ( i.e. NOx) is a normally open pin , NCx pin is normally closed , COMx is common, i.e., when the relay is not driven , NOx and COMx open between two pins , NCx and COMx connection ; When the relay (x) control signal pin is high drive relays , NOx and COMx connection open between NCx and COMx.

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