Lysignal DC 5V 8 Channel Relay Module Interface Board for 51/AVR/AVR/ARM with Optocoupler Protection

Although this relay board comes without wiring instructions, you can work out the wiring with a little experimentation. The pinouts are:Vcc - Positive voltage connection to optical isolator and indicator LED.RY-Vcc - Positive voltage connection to relays (can be same as Vcc if jumper used to connect them, see below).GND - Ground (low voltage connection) to relays.IN1...IN8 - connect to digital I/O pins on microprocessor. Voltage high is off (note the orientation of both the indicator LED and opto-isolator LED: IN1...IN8 must be at low voltage for them to be forward biased and therefore switch on). IN1..IN8 act as the low voltage connection to the optical isolator and indicator LED when the corresponding digital I/O pin is set to low.COM - common pin of relay. Connect whatever you want switching to this pin for normal operation.NC - Normally closed pin of relay. When the corresponding digital I/O pin on your microcontroller is high, the relay is 'off' which means the NC is connected to the COM pin.NO - Normally open pin of relay. When you set your Digital I/O to low, the optical isolator switches on the appropriate relay (via transistor T1) which disconnects NC and connects NO to the COM pin.There are therefore two main ways in which you can switch the relays - one of which provides optical isolation between the microprocessor power supply and the relay power supply, and one of which does not. I've drawn up a couple of schematics to show the difference (only one channel is shown for clarity).In the non-isolated setup, the GND and 5V outputs of the microprocessor are connected to the GND and Vcc of the relay board respectively. The jumper is then used to connect the Vcc and the RY-Vcc pins so that both the relays and the optical isolators are powered from the same source.In the isolated setup (useful e.g. if your microprocessor can't supply enough current to operate all of the relays and optical isolators / LEDS, or if you are experiencing noise in your circuit):1) The jumper is REMOVED.2) The GND connection between the microprocessor and Relay board is REMOVED.3) A SEPARATE power supply is used to power the relays. Positive is connected to RY-Vcc and negative to GND.The relays are operated in exactly the same way via the microprocessor, but this now only turns on / off the optical isolator. The isolator then switches T1 on/off and power to the relay is provided by the separate power supply. Hope this helps!

No problems at all with this relay shield, switching currents below an amp anyway. In use for a couple of months now

Dose the trick but with all relays engaged it is a little current heavy will need a bigger power supply for most applications the board is neat and glad to see it has air gap brakes for use in 230v applications if desired but use at your own risk.

I bought two of these and both of them have intermittent contact faults.

Ad you described 👏👏👏👏👏

Spot on