safety rules
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Posts: 46,084
Hello,
There some rules how to insure safety for equipments with both 220V mains
and low level signals on the same board,where can I get these rules?
Thank You
Mohamed refky
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There some rules how to insure safety for equipments with both 220V mains
and low level signals on the same board,where can I get these rules?
Thank You
Mohamed refky
_________________________________________________________________
MSN Photos is the easiest way to share and print your photos:
http://photos.msn.com/support/worldwide.aspx
Comments
The first rule is keep the high voltage seperate from the low voltage !
The second rule is keep the high-voltage wires away from humans !
The final rule is keep the high-voltage wires away from the stamp !
The only common wiring to both high and low, is usually the mains ground
wiring which would be connected to the "earth" or "shield" for metal cases.
In the case of a plastic box, there is no need to wire the ground wire to
anything.
Usually, in stamp apps, the mains is used for two reasons:
1. To provide mains power to the stamp.
2. To switch mains power on and off
In the case of (1) - use a wall cube, it takes the worry of high-voltage
away.
In the case of (2) - use a relay with contacts rated for mains voltages and
an ampere rating at least twice the required rating at AC. Keep the mains
wiring to the relay short, and well clear of any other cables. Wwhere
possible, use rubber or plastic "boots" to cover bare connector wires. Use
wires of sufficent amp rating - as per the relay contacts. Use a fuse in
each lead - rated at 1.5 to 2 times the expected equipment load. Use plastic
panel mounted fuses.
HTH
Tony
Original Message
From: "Mohamed REFKY" <refky@h...>
To: <basicstamps@yahoogroups.com>
Sent: Friday, June 07, 2002 8:25 AM
Subject: [noparse][[/noparse]basicstamps] safety rules
> Hello,
> There some rules how to insure safety for equipments with both 220V mains
> and low level signals on the same board,where can I get these rules?
>
> Thank You
> Mohamed refky
>
>
>
> _________________________________________________________________
> MSN Photos is the easiest way to share and print your photos:
> http://photos.msn.com/support/worldwide.aspx
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
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>
>
>
If safety is your concern this may help, If not, forgive my blabbering
on....
There are great differences between a one-off, or hobby design and a
production design. Too often someone sets off with a great idea that
backfires because they fail to ask the question you just posed.
The set of "rules" you will choose to follow depends upon where you intend
to use and sell your product. If in the US, look up the UL standard for
either the product class or one of the more generic standards for electronic
assemblies. If your target market is more international, you might search
for the appropriate ISO standards.
As advanced warning, it is not likely that you will find everything you need
in one standard, so you will need to buy copies of each that you suspect
will have pertinent info. Standards copies are ridiculously high-priced.
As an alternative, you could hire an experienced standards engineer to
either do your final design, or advise you along the way.
BTW, this is what I do for a living....
Hints I'm willing to give are :
1. Always use line or mains connected components that already have agency
listings or approvals. Then research the criteria that determine whether or
not your use of them is within the terms of the listing or approval.
2. Common to UL standards are two tables for primary circuit spacings and
field-terminal spacings. Field terminals at 220V are therein required to be
1/4 inch apart either over surfaces or air. Other primary wiring at 220V
must be 3/32 apart.
3. There are a good number of other factors that have to be considered, such
as PCB trace weight and thickness, the effects of different types of solder
mask, temperatures of the enclosed assembly, etc...
4. My own rule: Optically Isolate mains from signals whenever possible.
I would follow these even if I was building a one-off.
I got into this some years ago when I realized how costly and time-consuming
it is to design a LEGALLY safe product on my own. It is definitely faster,
hence less costly to get expert advice if any level of production is being
considered, and one wants to avoid future litigation.
Rgds,
Chris
> Hello,
> There some rules how to insure safety for equipments with
> both 220V mains
> and low level signals on the same board,where can I get these rules?
>
> Thank You
> Mohamed refky
>
>
>
>
components for optical isolation, PC board hourses, enclosure mfrs, and
even strain reliefs should all be UL listed, or you will be facing a
re-design problem. Been there done that. Hiring a standards engineer
early on saves time and money down the road.
Dennis
Original Message
From: Chris Loiacono [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=b6xZkueML3Yq7BltOfq1gyS7fbwcou5rrnJHcGXPH_p5xSoXLao4Lf_yHH4amSNftyUZ8HmUoHdUt2UP]chris@m...[/url On Behalf Of Chris
Loiacono (E-mail)
Sent: Friday, June 07, 2002 11:31 AM
To: basicstamps@yahoogroups.com
Subject: RE: [noparse][[/noparse]basicstamps] safety rules
Mohamed:
If safety is your concern this may help, If not, forgive my blabbering
on.... There are great differences between a one-off, or hobby design
and a production design. Too often someone sets off with a great idea
that backfires because they fail to ask the question you just posed.
The set of "rules" you will choose to follow depends upon where you
intend to use and sell your product. If in the US, look up the UL
standard for either the product class or one of the more generic
standards for electronic assemblies. If your target market is more
international, you might search for the appropriate ISO standards.
As advanced warning, it is not likely that you will find everything you
need in one standard, so you will need to buy copies of each that you
suspect will have pertinent info. Standards copies are ridiculously
high-priced.
As an alternative, you could hire an experienced standards engineer to
either do your final design, or advise you along the way.
BTW, this is what I do for a living....
Hints I'm willing to give are :
1. Always use line or mains connected components that already have
agency listings or approvals. Then research the criteria that determine
whether or not your use of them is within the terms of the listing or
approval.
2. Common to UL standards are two tables for primary circuit spacings
and field-terminal spacings. Field terminals at 220V are therein
required to be 1/4 inch apart either over surfaces or air. Other primary
wiring at 220V must be 3/32 apart.
3. There are a good number of other factors that have to be considered,
such as PCB trace weight and thickness, the effects of different types
of solder mask, temperatures of the enclosed assembly, etc...
4. My own rule: Optically Isolate mains from signals whenever possible.
I would follow these even if I was building a one-off.
I got into this some years ago when I realized how costly and
time-consuming it is to design a LEGALLY safe product on my own. It is
definitely faster, hence less costly to get expert advice if any level
of production is being considered, and one wants to avoid future
litigation.
Rgds,
Chris
> Hello,
> There some rules how to insure safety for equipments with both 220V
> mains and low level signals on the same board,where can I get these
> rules?
>
> Thank You
> Mohamed refky
>
>
>
>
To UNSUBSCRIBE, just send mail to:
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UL60950. It is a bi-national standard so if you comply with it you have
complied with requirements in Canada for the most part. It is also
harmonized with EN60950 so in most cases you would comply with the
European Norm too. Getting the document is rather pricy. UL also offers
a practical application guide (PAG) for UL60950 that is very helpful in
understanding the application of the standard. UL60950 replaced UL 1950.
If you can find an old copy of UL1950 and read it you will a very good
idea of what is required. If you have not designed a product to comply
with the UL or EN standards you might look at hiring a safety engineer.
It will save you time and money over the long run. Check out WWW.UL.com
(it might be www.ul.org). Good Luck.
On Fri, 07 Jun 2002 10:25:36 +0300 "Mohamed REFKY" <refky@h...>
writes:
> Hello,
> There some rules how to insure safety for equipments with both 220V
> mains
> and low level signals on the same board,where can I get these rules?
>
> Thank You
> Mohamed refky
>
>
>
> _________________________________________________________________
> MSN Photos is the easiest way to share and print your photos:
> http://photos.msn.com/support/worldwide.aspx
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the
> Subject and Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to
> http://docs.yahoo.com/info/terms/
>
>
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