mains isolation distance on PCB

[Kram]

Hello

What regulations are there reguarding the use of both mains connected equipment and low voltage (mains isolated) components on the same PCB that are connected with each other by opto isolators and relays.

I think that there is some seperation distance required but I dont know what it is or where to find the details. IEE regulations or CE rules or something like that.

Does anyone know? Im in the UK as well just in case there is any difference between US and UK regulations.

Thanks
Mark

 

[Frank Berry]

I'm not sure that there are any regulations that pertain to DIY equipment. I think the regulations only apply to equipment that is manufactured for sale.
As a rule of thumb however, I don't like to mix mains voltage on the same board as isolated voltage.

 

[Kram]

Probably should of mentioned that is is for my uni project and therefore has to be correct.

I have to justify every design choice I make. So when I am writhing the report I can say that the PCB confirms to such and such a standard.

Thanks
Mark.

 

[richie00boy]

If you Google for UK Creepage and Clearance distances I think that will help. IIRC from my brief stint as a small company CE Mark compliance manager/engineer (almost 10 years ago now) that the distance live-earth (for class 1 (earthed)) and live-case (for class 2 (isolated)) equipment is 6mm, so I would presume that it's safe to use this distance for live-lowlevel.

You would be better off researching this properly to make sure you quote the current standard as this will look impressive in your report. I was working to BS-EN60065 back in the day which I believe has now been superseeded.

 

[Kram]

thanks richie00boy,

there seems to be some info on what im after on the IEE website but you have to pay for it, DOH!

Anyway im going to see my tutor now so hopefully he will be able to point me in the right direction.

Thankyou
Mark

 

[Enzo]

Industry organizations may sell copies of the standards, but it is the government that requires their following. I would suspect the government will provide the specs for free.

Hopefully the Europeans standards are all converging, because there is such an alphabet soup of certifications now. US and UK do indeed have differing standards on many things in this area.

 

[Kram]

Hello

one of my tutors has suggested that I look at ISO9000 but I will have to search for a relavent answer. Why are things never easy to find

Thanks
Mark

 

[peranders]

If can touch anything in the secondary circuit the insulation must be 4000 V and 8 mm creepage distance to the mains side.

 

[Kram]

The opto isolators im using to connect between the triac gate and the low voltage side are the MOC3020 and they only come in a standard 6pin dual in line package.

The MOC3020 is mounted in a standard 8 pin socket, so therefor the maximum distance between mains connected parts and low voltage parts is the width of the socket, approx. 8mm.

here is my PCB layout in case anyone can spot anything that is dramatically wrong with it.

 

[peranders]

There are opto couplers with extended "grid". Just check those types with lot's of approval markings.

BTW: Kram = "hug" in swedish

 

[JochenH]

ISO9000 series won't help you because it is no technical norm. Look after EN/IEC-60950-1 or IPC-2221A, but i don't know where to get them free.

Jochen

 

[Kram]

I had a look at some info on the ISO 9000 and it mostly seemed to be about getting your business managment to be in compliance with ISO9000. A bit strange I thought.

Anyway JochenH I will search for the standards you have suggested and see where I get.

Thanks
Mark

 

[sam9]

one of my tutors has suggested that I look at ISO9000

That won't help. ISO9000 just requires that procedure be documented and that the actual practice conforms to the document.

 

[pinkmouse]

Here's an article from EDN that covers some of what you need to know.