Variable Power Supply

[rolycat]

Then perhaps you should inform companies such as Tivoli Audio who still build domestic radios and hi-fi into wooden enclosures.

Why? I don't have any knowledge how these radios are constructed internally. Maybe the PSU is housed in a metal compartment shielding it from the wooden case. Who knows ...

Because you stated categorically that "domestic installations are not allowed in wood enclosures". And then edited that incorrect statement out of your reply.

Wood is not an approved insulator as its properties vary with the sort of wood and moisture etc. etc. and are hard to control.

In the described project, I do not see any form of double insulation within the case.

So yes: For that purpose: Wood is definitively not recommended!

For god sake, you can enclose ANY enclosure (conforming to your local norms) inside a wood box if cooling is sufficient. But to the best of my knowledge, wood should never be used to insulate mains voltages (As it has been in this case!). Maybe however, to block access ...

I think you will find that nowhere did I suggest that the Make magazine project was in any way an example of good design, or that wood is a safe insulator for mains voltages.

[homebrew]

Because you stated categorically that "domestic installations are not allowed in wood enclosures". And then edited that incorrect statement out of your reply.

What on earth has gone wrong here? I did never "edit something out" of any reply !? 

Yes absolutely "domestic installations are not allowed in wood enclosures". At least where I do live (Europe). Here you cannot install a plug in a woodern cabinet without housing it in a plastic or metal box.

[rolycat]

Because you stated categorically that "domestic installations are not allowed in wood enclosures". And then edited that incorrect statement out of your reply.

What on earth has gone wrong here? I did never "edit something out" of any reply !? 

Yes absolutely "domestic installations are not allowed in wood enclosures". At least where I do live (Europe). Here you cannot install a plug in a woodern cabinet without housing it in a plastic or metal box.

The fact that English is (presumably) not your native language may have caused some miscommunication. However, the fact remains that wood is a perfectly suitable material for mains powered electrical enclosures. It goes without saying that this is only true if it is employed by a competent designer, since this is true of any material.

The last time I checked the United Kingdom was part of Europe, and here at least my understanding is that mains voltages can be present in a wooden cabinet as long as they are safely insulated and any conductive penetrations are properly earthed. This does not mean that the entire cabinet has to be lined with either metal or plastic.

If you have specific information to the contrary I would be grateful if you could supply a reference.

[liquibyte]

I finally got the simulation to behave like I wanted.  I'll have to test this in the real world but this is the kind of thing I was after.  Next up, fixing the CC/CV to be more in line with established designs so I'm off to research and model various solutions to see what I can come up with.

The usual solution is to wire the outputs of the two error amplifiers together with some diode OR logic; then either amplifier can pull the output down to limit either the current or the voltage.  This causes the amplifier which is not currently controlling the output to saturate but recovery time is generally fast enough for this not to be an issue and the output transitions seamlessly between constant current and constant voltage mode.

I did some looking around and found various examples of diode logic and can now say I understand it.  What I can't wrap my head around is how to split this apart to apply that in this circuit.  I tried for several hours last night but I think this would really benefit from this if it was redesigned from scratch.  More study is in order.

[AG6QR]

Then perhaps you should inform companies such as Tivoli Audio who still build domestic radios and hi-fi into wooden enclosures.

Why? I don't have any knowledge how these radios are constructed internally. Maybe the PSU is housed in a metal compartment shielding it from the wooden case. Who knows ...

I own a Tivoli model one radio.  I've opened it up in order to clean a dirty volume pot that became scratchy after a decade and a half, and I can report that it has mains inside the wooden box without a metal shield.  I don't have teardown photos myself, but a quick google search led me to this web page where someone else has photos of it.

http://la3za.blogspot.com/2013/12/scratchy-tivoli-audio-model-one.html

The first photo on that listing is showing the radio with the wooden case removed.  You can see the power transformer.  The mains cable is a two-wire one, with no ground lead.   Note that the front and back panels are plastic, while the top, bottom, and sides (removed in that photo) are wooden.

By the way, that site appears to have been written by LA3ZA, a ham radio operator from Oslo Norway.  So if this radio design is faulty, it apparently got through the regulators of at least two countries (I'm in the USA).  I don't know a great deal about this area of regulations, but there's nothing about this radio that stands out to me as an obvious safety hazard.

But this radio isn't high powered, and doesn't produce a lot of heat in operation.  While I don't see a problem with this particular wooden case, I would be cautious about using wood to enclose a linear regulator that could be running close to its thermal limits. 

[rdl]

Funny, I have a lot of stuff that plugs into a mains outlet in the wall. None of them have metal enclosed power cords.