I would just like to ask if my wirings for a power control box is correct. I am planning to power 4 independent outlets to actuate pumps and other devices on mains, and control these independent outlets using a 5v relay for an automation project. With that, by what I understand I should wire the four outlets in parallel to independently switch the four AC channels. Here is my wiring so far

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I've split the power cable to take the live wire to connect it to the NO port of the relay (most right), and share the power to the other three as shown in the connection. From there, I'll connect the individual COM ports to a respective outlet on its Live connection. I would just like to confirm if the neutral (blue) wire is supposedly as shown?

By what I understand, the GND lines should connect as such to share current return paths, but as for the neutral I am not entirely sure but I do understand it works similar to GND as well for providing current return path. Moreover, I also plan adding a fuse or some type of breaker in the future to provide extra safety for the circuit. As for now, I am connecting the plug to an OMNI extension outlet which provide safety switches and built-in breaker as well.

The relay is opto-isolated, working for 250VAC 10A max rating, where in our country, 220V 10A is provided off mains. Similar max ratings with the outlet.

Thank you very much for any response in advance.

  • \$\begingroup\$ Which coutry this is, or rather, what kind of mains sockets are those? Even if it looks technically correct, I would consider switching only one wire of the socket a safety hazard and would switch both wires of the socket. \$\endgroup\$
    – Justme
    Feb 20, 2022 at 9:19
  • \$\begingroup\$ Philippines. These are Bull 2 gang universal sockets, 250V 10A, here is a link locally shopee.ph/… \$\endgroup\$
    – Guorishix
    Feb 20, 2022 at 9:24
  • \$\begingroup\$ It seems that is a polarized socket, so in theory, which pin is live should be guaranteed. But when existing sockets are miswired, disconnecting only one wire means your box cuts only neutral and live still goes to all devices which is a hazard. Make sure what the regulations in your country are, is it enough to switch only one wire or do you need to switch both L and N for safety reasons. \$\endgroup\$
    – Justme
    Feb 20, 2022 at 10:05
  • \$\begingroup\$ I believe only the live wire should be switched here. Regardless, do correct me but, shouldn't the neutral also be grounded as well? as mentioned also in local standards it says that we're also using a grounded system. Moreover, I've actually tried this using one socket and only the live wire was being switched to actuate my device. \$\endgroup\$
    – Guorishix
    Feb 20, 2022 at 10:25
  • 1
    \$\begingroup\$ The neutral is earthed already at some point in your electrical system. Your box must keep them separate. If you are unsure how to build this safely then please don't build it. \$\endgroup\$
    – Justme
    Feb 20, 2022 at 10:36

1 Answer 1


The GND/Earth wires are for safety - no current should flow in them except when there's a fault. The normal return path is the blue neutral. Do not confuse mains gnd/earth with the one on your electronics!

You need to be careful with those generic relay boards. Many of them are not safe or suitable for connection to the mains network due to insufficient creepage distance. The rating on the relay case is for the relay, not the assembled circuit. How are you going to mount the relay board and ensure safety? You don't want to burn down your house and/or electrocute yourself.

I can buy complete WiFi controlled power outlets for far less than I could assemble one. I do not have to touch any mains wiring and the circuitry is certified to local standards. I'd suggest you find something similar in your part of the world and avoid potential problems.

  • \$\begingroup\$ I do plan on connecting the plug off an extension outlet with built breakers, and have the whole circuitry inside a junction box. Screwing the boards on some type of panel inside to ensure it's all fixed. I thought that those setups would suffice. As for the wires, yes, I do understand the neutral and GND wires are different. I understand and will consider doing the wireless approach, but for clarity, so the neutral wires are correctly wired ensuring each outlet is independently switched? \$\endgroup\$
    – Guorishix
    Feb 20, 2022 at 7:55
  • \$\begingroup\$ I've actually controlled using one outlet before this, now i'm hoping I could use the same setup for controlling 4 channels though I'm just quite not sure if the parallel connections for the return paths are correct. \$\endgroup\$
    – Guorishix
    Feb 20, 2022 at 7:57

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