When designing a PCB for a low-voltage circuit that connects to the mains, how much clearance must be used between the mains or primary side and the low-voltage or secondary side of the circuit? This may sound like a trivial question but, unfortunately, it isn't. A typical example would be a mains-switching relay controlled by a microcontroller. (Do you know you can back this project? It is an Elektor Jumpstarter!)

In the first part of this series, we concluded that IEC 62368-1 is the safety standard that applies to our situation. It provides a number of criteria to determine the clearance and creepage distances. In part two we will have a close look at every one of them.

Resources & Links

- IEC 62368-1 draft 4b
- IEC 62368-2 draft 4a
- Clearance & Creepage Part 1
- Clearance & Creepage Part 2
- Clearance & Creepage Part 3