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I've designed some PCB's in the past but never really had to worry about load and safety. Now I need to build a small PCB with some 230v AC cirquits. The load will be minimal, but still I have healthy respect for working with AC voltages.

What I need is a few simple push button switches that send an impulse to a connected device. the load here will be about 0.5 Watt.

1) I'm assuming this can be done on a PCB. How do I go about figuring out how wide to design my tracks and what are safe distances?

2) are there any really small push buttons out there (in the 6mmx6mm range) that are able to deal with these voltages? everything I find has contact ratings at 12v.

Thank you for your advise!

EDIT: Let me add some context. I have a bunch of in-wall-switches that I've upgraded to smart switches by adding a Sonoff Mini behind them in the mounting box.

in this setup the original switch functions as signalling switch to the Sonoff, on the Sonoff the swich port is 3.3v DC (i think, might be 5v).

So far, so good.

But, because the space in some of my mounting boxes is very limited I can't always do it like this because the combination of switch plus sonoff is just too deep to fit.

Here comes my project. I've designed and 3d printed a setup that replaces the switch with a plastic contraption that allows mounting of the original switch face plate and that houses 2 micro switches. This saves 15mm of depth compared to the original setup and works great!

my 3d printed jig

All was good in my life.

Now i want to do the same with a Shelly dimmer which is connected thus: Shelly setup

So, the Shelly switch port functions at 230v AC. I contacted Shelly, they gave my the 0.5w specs. (i will measure myself when i receive my dimmers). clearly I can't just hookup my jig now.

So, i'm looking to come up with a solution for this limited space, potentially 230v setup problem. preferably i will over engineer it, because, you know... I can :)

palloquin
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2 Answers2

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1) Trace widths depend on amperage, clearance on voltage, you can find many calculators and tables online, e.g. (based on IPC-2221 norm):

Standard PCB trace widths?

Minimum clearance between two traces that have a potential difference of 1000VDC

Generally when using traces for power distribution, you can go "as wide as you can" to avoid power losses and when using dangerous voltage, keep the clearances as big as you can unless you really need to cut down on PCB dimensions.

2) Never seen such, bigger and more robust ones of course exist. Also if you want to have a small button switching directly 230 V on its pins on a PCB, I would keep my hand far away from it. I would probably use a small button triggering triac or relay if you have some DC voltage available on the PCB. Differences are well described here:

Triac versus Relay

MartyCashew
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This question was recently addressed here: Mains voltage PCB design

That said, I suggest using a relay to control the 230V, and use low-voltage push-button switches to control the relay. Then the high voltage is kept far away from human touch.

hacktastical
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