What would be the best way to energize 20 timer relays

Projects General Guidance
1

Gentlemen, I would like some help.

In my project I'm using a mega arduino along with some relays. Being that I would like to feed these relays with an external source. However, these relays only have two forms of power: through a microusb port or through the pins.

The intention is to use a single source for approximately 20 relays. So, I ask you: what is the best way to feed these relays?

https://www.gearbest.com/other-accessories/pp_625459.html

I have never seen a power supply with 20 micro-usb cables and I do not know if I connect the V + and V- cables to the power supply will work. The question in this regard is: where does the current flow by using an external source? I know that the Arduino pins work with a maximum of 40mA. Then it is through the IN pin that the current arrives. Or not? But if we connect an external source will not pass current from the Arduino to the board through the IN pin? What would I need to make a link as below work?

If I use a protoboard with external source, would the current be drained from the protoboard?

What would be the best way to energize these relays?

2

Your diagram looks OK except that you need to connect the GND to the Arduino GND. You should be able to use a USB 5v power supply. You may need to make up your own cable to connect it to the red and black wires in your diagram. Get a power supply that can provide about 2 amps.

Another option (probably only suitable for testing) is to power the relays from 3 x AA alkaline cells (4.5v) or from 4 x AA NiMh cells (4.8v).

...R

3

You can use any power supply, from 5-30V, with these modules. The 5V IMO apply to the signal pin (TRIG) level only. As Robin already mentioned, connect V- to both the power supply and the Arduino Gnd.