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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 still use it with some changes.

enter image description here

I'm thinking of using 2.54 m right-angled female headers and connect them to the screw terminals. But I don't know if they can handle 220V. And my track spacing towards the end is too less for 220V, 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.

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  • \$\begingroup\$ At 230Vac, the minimum clearance should be 2-2.5mm for basic insulation. Remember that this is for uncoated tracks and pads. You can increase the insulation by drilling slots between pads like shown here. Of course it's not easy to make it a slot. You can at least drill a hole without deforming/damaging the soldering pads. \$\endgroup\$
    – Rohat Kılıç
    Jun 6, 2020 at 21:24
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    \$\begingroup\$ You could paint over the 3 pin headers with something (for insulation), and then solder directly to the relay pins on the bottom of the PCB? Or you could cut the traces after they pass out from under the relays, and then scrape away the solder mask to make new pads that are farther apart. \$\endgroup\$
    – Drew
    Jun 6, 2020 at 22:36

2 Answers 2

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  • Drill extra top and bottom holes (green) to place a 5.08mm (or 5mm) pitch screw terminal block
  • Cut and remove the trace to the unused holes (sky blue)
  • Cut slots (green) to separate the coil terminals from the relay common
  • Add wires (white) linking the unconnected relay terminals to the terminal block
  • That LED will need to be moved too, and its wiring ripped up

enter image description here

Next time consider using relays that have the contact terminals at one end and the coil terminals at the other end, eg NAIS JW1 series or Omron G5Q series.

The ESP module works best if there is no PCB under its antenna and especially no planes or traces. so you may want to relocate that 5V line too.

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  • \$\begingroup\$ Yup. Board rework like this is just another skill to acquire, like debugging. \$\endgroup\$
    – user16324
    Jun 7, 2020 at 10:52
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You can use a "pcb lacquer spray" to cover the pins where creepage distance is not enough. Most 2.54 connectors don't have the distance so they might need to be modified anyway or wired to a wire connector and protected with potting compound, lacquer won't secure a flexing wire connection.

0.5 A doesn't need a very thick track. You can use an online PCB track width calculator to see the power loss, but it looks like you are going to be fine.

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