Separate power supply for 8 channel ac relay

Hi everyone,

I'm working on a home automation/ iOT project where I need to power some ac components with a relay. From my research it seems like the best way to accomplish this is to provide a power supply for the relay to keep the Arduino separate from it in terms of power.

I found a video where a guy just used an old cellphone charger and attached jumper pins to the end of the bare wires, but I want to make an informed decision about the parts I'm using and not just hope what I have lying around will work. How do I determine the best way to provide power to my relay? The model is this one: https://www.amazon.com/Huayao-Channel-Optocoupler-Arduino-Raspberry/dp/B07DNB2NGD/ref=sr_1_1_sspa?keywords=8+channel+relay&qid=1558719163&s=electronics&sr=1-1-spons&psc=1

Thanks for your help in advance!

A good way would be to use an external supply that supplies the Arduino directly with 5V since those relays work with 5V as well (1A sure would be way more than enough). That way you could wire 5V and GND of the relays to the 5V and GND of the Arduino board you're using.

In case you're using a 3.3V logic Arduino board you may want to use transistors or MOSFETs to turn On/Off the relays.

F1_:
A good way would be to use an external supply that supplies the Arduino directly with 5V since those relays work with 5V as well (1A sure would be way more than enough). That way you could wire 5V and GND of the relays to the 5V and GND of the Arduino board you're using.

You can power a relay board and an Arduino from a single 5volt supply, but don't power an 8-relay board (8*75mA) through an Arduino.

Note that you can't have opto isolation with a single supply.
Might be important (extra safety) if you switch mains power with the relays.

You only have opto isolation if you power the relays from a separate 5volt supply (JD-vcc and relay ground),
have the JD-vcc jumper removed, connect relay vcc (not JD-vcc) to Arduino's 5volt pin,
and DON'T connect relay ground to Arduino ground.

F1_:
In case you're using a 3.3V logic Arduino board you may want to use transistors or MOSFETs to turn On/Off the relays.

No. Look at the board's circuit diagram.
The opto LED and indicator LED threshold makes direct connection to 3.3volt logic possible.
Relay vcc must be connected to (Arduino's) 5volt though.
Leo..