Hey everyone. I recently designed my first PCB, which uses an ESP-01 to control 4 relays. I planned to use this to control my home appliances, which run at 220V. But I made a rookie mistake, instead of placing screw terminal width holes for the relay's COM, NO and NC terminals, I placed standard 2.54 mm spaced holes. I have the ordered (and received the) PCBs already, so was wondering if I can use it with some changes.



I'm thinking of using 2.54 m spaced screw terminals. But I don't know if they can handle 220V. And my track spacing towards the end is too less for 220V, but is it safe enough for a maximum current flow of 0.5A?

I do not wish to waste these PCBs, so any suggestions on how to use/modify them will be highly appreciated.

And what's the worse that can happen? If my PCB gets a short circuit or something, I believe my appliances will turn on even if the relay is off. Or maybe some other problem can destroy the PCB or damage the components (which are cheap). But can anything riskier happen?

Thank you.

 

Did you look at the data sheet for your screw terminals. 2.54mm is small. I might use a 5 pin with pins 2 and 4 removed.

If you have a flashover across the relay traces, maybe a light is on. You really do not want a spark from power line to ESP-01S. I would increase the space where I circled.
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For safety, the PCB track spacing between your 220V mains and low voltage (SELV) circuits should be at least 4.4mm.

Looking at the track layout, you may not meet this where the low voltage tracks come close to the relay contact solder points. The pin-out of the relays (with the common switched terminal close to the coil terminals) may mean that it is not possible to meet the above requirement with the relay model fitted.

 

For safety, the PCB track spacing between your 220V mains and low voltage (SELV) circuits should be at least 4.4mm.

If you have a flashover across the relay traces, maybe a light is on. You really do not want a spark from power line to ESP-01S. I would increase the space where I circled.

And what about the spacing between the 3 mains voltage terminals of each relay (NO, NC, COM)? What are the chances of a flashover there?

 

Even the named terminal Manuf, such as Phoenix Contact and Weidmuller only rate the 2.54mm to 160v .
Max.

 

Weidmuller only rate the 2.54mm to 160v

Yes. 120ac has a peak of 1.414x120=
I have some of these boards. As you can see the ac connections are larger than 2.54mm.

Here is the back side of another board. They could not get spacing so they cut a slot in the board so air is the insulator not the PCB.

 

The problem with the substandard separation distances (between mains and SELV) is not so much a ‘flash-over’ event – but due to a failure of the insulation, the SELV circuit becomes live with a potential electric shock hazard from the SELV circuit and anything connected to it.