How much copper for AC mains

if the breadboard test goes through, how much weight copper would be ideal for a single sided copper clad board where a trace for AC mains is used. The load will be an MOT. The layout is show below.

Insufficient information to give an informed answer but you might find what you want here

If you order this through a board house, then you could make the current carrying tracks double sided.
And maybe also the transformer pins/tracks, for extra mechanical strength.
Leo..

anishkgt:
if the breadboard test goes through, how much weight copper would be ideal for a single sided copper clad board where a trace for AC mains is used. The load will be an MOT. The layout is show below.

Hi,

Normally trace sizes are based mostly on the current handling requirement. In a device that handles AC from the mains you should have a fuse inline and that will have a rating that will specify how much current will be allowed to go though the traces. From there you can calculate the required trace width. If you do not have such a fuse they you really should base it on your areas electrical outlet specification max. For example in most parts of the US the max is 20 amps for a regular home circuit. For an industrial application it could be much higher though and a fuse would really be mandatory. In fact, i would not build a device that connects directly to the mains without a fuse no matter where it was to be used.

Track width and thickness depends on current.

For mains voltage isolation separation is what is important.

There are various standards for this ranging from 1.5 to several mm, depending on humidity etc. and coating.

For a bare board i have seen it mentioned that 5mm is considered safe.

1.5mm is utterly inadequate for mains separation unless you have a proper conformal coating which
is unlikely. Start with more like 10mm, and consider using cutouts too. The kind of spike voltages that
occur on mains wiring when fluorescent lights or motors switch on and off and during thunderstorms
are measured in kilovolts. Its a great idea to incorporate a transient suppressor (MOV) to help prevent
destructive spikes in mains PSUs.

MOT? ministry of transport?

I took that to mean metal oxide transistor.

Another thing to consider is the enclosure , IP rating.
Unfortunately the standards covering these things cost money to read.

On the rare occasions i have done it i always used a coating.

Best to use a wall wart if you can and avoid mains wherever possible.
And preferably put any opto isolators at the 'hot end'.

MOT = Motor?

thanks guys with the feedback. MOT stands for Microwave Oven Transformer, hobbyist use it to weld battery tabs.

The 5mm is actually the width, i was referring to the weight of the copper like how many ounce ? if could get that i could check with some ebay sellers.

Yes the traces will be covered with solder mask and a few cutouts too will be made. My AC mains are rated at 240Vac.

anishkgt:
The 5mm is actually the width, i was referring to the weight of the copper like how many ounce ? if could get that i could check with some ebay sellers.

1 Oz is the common one.

2 Oz is available at a price but uncommon.

thanks

Can't really make up my mind between that 1oz or 2. For my layout attached in the first post would 1oz be ok ?

I have the TVS added at the mains before the transformer and a 2A PTC at the secondary.

If your MOT draws 10 A (you need to measure , i do not know)

2 Oz requires a 10mm wide track.
1 Oz requires a 19mm wide track.

2 Oz are likely to be expensive to have made anyway.

PCB i suggest is NOT suitable for this especially if you have to ask.
Use cable.

The spacing between the pins of your connector blocks is also too small to use without coating.
Solder mask leaves the pins bare and arcing or bridging can still occur.

In a cold workshop where these devices are used there could be condensation.

Your trace size must also consider "duty factor". Tab welding on batteries would be quite intermittent, so the duty factor is quite low. The trace sizes that have been discussed are based on 100% duty factor. The problem is heat generated by the resistance of the copper trace. Low duty factor means low heat generation.

Paul

anishkgt:
Can't really make up my mind between that 1oz or 2. For my layout attached in the first post would 1oz be ok ?

Use an online calculator.
1oz, double sided, would need 2mm (80mil) width for 10Amp, if ~25C temp rise is acceptable.
If you're really that worried, then order the power tracks uncovered with soldermask, so you can thicken the tracks up with solder afterwards. Common practice for power tracks.
Leo..