On 14/04/2018 23:42, Roger Hayter wrote:
Roger Hayter wrote:

dennis@home wrote:

On 14/04/2018 21:12, charles wrote:
8

a 6v transformer is just a transformer. Isolating transformers do just
that _ they isolate - mains level voltage on the output. Used to be
an essential workshop item when dealing withn live cahssis equipment.


Not all transformers are isolating!
Why do you suppose I said an isolating transformer rather than an auto
transformer or any other type with a single coil?

Not all, but nearly all! Except for special applications for
autotransformers, most applications require not only isolation but an
insulation resistance tested to some insulation resistance standards,
if only to avoid killing people who touch the secondary circuit and/or
tripping RCDs when the secondary circuit is permanently or transiently
connected to earth. Reference to an "isolating transformer" tends to
imply one used *only* for isolation with a one to one ratio of turns.

FAOD, I should have said nearly all *mains* transformers. There are of
course other kinds.



You can say what you like now, but this is a DIY group and some people
won't know what an isolating transformer does or why to use one. Only a
fool expects everyone in a public audience to understand what they say.
Don't give out advice on dangerous stuff unless you make it clear.

Its the same with the advice for 12V supplies people give out, there are
12V supplies that are isolated from the mains but there are some that
aren't and you really don't want the ones that aren't for "projects".
Its hard to tell on ebay/amazon what is and isn't live so I tend not to
buy them when cpc is just as cheap.