Project enclosure with IEC power socket?

[cellularmitosis]

I'm surprised I'm having a hard time finding this!

Are there any project enclosures which already have a IEC power socket (with switch and fuse)?

Actually, what I'm really after is a split-tap transformer which is already in a fused, switched, grounded enclosure with an IEC socket on one end and the three output terminals on the other end.  I also can't seem to find that.  I'd rather not deal with mains stuff myself, so if I can buy this as an off-the-shelf unit, great!

[homebrew]

First of all - great to see someone care about safety!

1) What are your specific requirements? What prohibits the use of a normal wall-wart and create a virtual ground? AC wall warts together with a half wave rectifyer would also give you a symmetric supply. But it all depends on the power requirements of your load.

Here is a list for tons of options: https://www.tubecad.com/2018/02/blog0412.htm

2) You could use one of the various DC-DC converters to create a negative rail or even a complete symmetric setup. But that also depends on your load.

[tkamiya]

There are companies that will take one of their standard project boxes, cut  holes customer asks for and sell it to you.  But if you are looking for something like that already done and you can order one off the shelf, I don't think you'll ever find it.

I had contacted one company I kept buying 2U rack cases.  I wanted IEC power socket and RS232C connector hole already made.  A rep said they'd do it.  But in the end, I didn't take that offer.  I just spent 3 hours in bathroom (where my machine shop is) making those holes.

[cellularmitosis]

wow, I had no idea there were that many options for virtual grounds!  I may have to consider that route.

as it turns out, I was able to find something -- if you search specifically for "audio enclosures", some useful hits come up https://www.aliexpress.com/item/4000844058877.html

my requirements are actually pretty meager: I'm just starting my journey down the rabbit hole of DACs and headphone amps, so a virtual ground might be fine.

[cellularmitosis]

"Here is a simple workaround: a center-tapped inductor, which we can locate within the enclosure. Non-center-tapped AC enters and the center-tapped inductor creates our ground terminal."

omg, what a brilliant hack

[james_s]

It takes about 5 minutes with a step drill and a file or nibbler to cut a hole and snap in an IEC jack. I don't think you'll find many enclosures that have that already, there are so many different styles of sockets and many designs will place them in different locations to clear internal components.

[ledtester]

I would check out your local Goodwill / thrift / surplus store for an old piece of electronics that has what you want. Then just replace the innards with your stuff.

[magic]

For small boxes like that the ultimate way to avoid messing with mains stuff is an external transformer. It also helps keep magnetic fields out. Look up, for example, the Objective2 power supply.

[coppercone2]

It takes about 5 minutes with a step drill and a file or nibbler to cut a hole and snap in an IEC jack. I don't think you'll find many enclosures that have that already, there are so many different styles of sockets and many designs will place them in different locations to clear internal components.

eh, if you want my take on things, those snap in jacks are crap, you drop the package and it breaks the snap in (not good for a mains connector IMO).

You need screw holes. Doing it with just a file is annoying, you pretty much need a deburring tool I think.

No one is going to do this off the shelf because the idea of electrical parameters being defined by box size is ridiculous, it could consume 50mA and do precision work or consume 20 amps and be a solid state relay box. Selling one would be insane. Not to mention, E-core, R core or doughnut transformer? what voltages? what VA?

Trying to find a market for a particular box of a particular size with a particular transformer is too much.

And you need to do the full mechanical design to know where to put the IEC connector in any box thats reasonably compact. Trying to fit components into a form factor is a HUGE job. Basically you would need to send the company drawings and schematics of the parts and then mail order the parts for them, its called a prototyping shop.

Have ANYONE do ANY layout work for you effects YOUR job. Better to design it yourself.


Also, once you put a few of these things together, you will see how much easier it is to do the job when you have the parts on a table and you figure out how the wires will go with good clearance and bend radius etc. Going too far from the shop SLOWS YOU DOWN.

[cellularmitosis]

So, it just occurred to me that you don't have to use a common-mode choke in common-mode: you could also use it as a 1:1 isolation transformer.

With that in mind, I could stick to using just one AC wall wart, and my PCB could have two chokes wired up to emulate a center-tapped transformer.

Are there any problems with this approach?  I suppose I need to learn more about impedance and inductance and magnetic saturation to determine how much power a choke can handle.

[cellularmitosis]

someone else had this idea back in 2013.  looks like the issue is finding a choke with sufficient inductance.  https://www.eevblog.com/forum/beginners/using-chokes-as-(non-mains)-isolation-transformers/

edit: ah, I didn't realize there were smaller isolation transformers available, intended for lower voltage SMPS applications.  Every time I searched for "isolation transformer", the only parts I could find were 110V mains isolation trafos.  https://www.digikey.com/product-detail/en/w%C3%BCrth-elektronik/750314597/1297-1165-1-ND/5700109

Perhaps the best route would be to just learn more about trafos and magnetics and wind my own?

[cellularmitosis]

I spent a minute fooling around with the "charge pump" rail splitter.  Looks like it works!

https://www.tubecad.com/2018/02/blog0412.htm

[wizard69]

This is one reason to keep an eye on used stuff.    Especially instrumentation built in standard enclosures, just reuse what is there.

Obviously there is a bit of luck in going the used route.    Considering that you could contact a panel contractor like: https://www.frontpanelexpress.com/.    That might not be worth it to you and you are still left with installing and wiring everything up.

Ultimately your best bet is to learn how to properly work with mains power.    It really isn't that difficult especially if you are going only to the power transformer.    Sooner or later this will be the right way to go about a project.

As for wall warts these can be ideal in some cases.   They are available in so many types and grades that it is very likely that one exists that already has the proper voltage and current levels.   I don't particularly care for this route for the simple reason that wart and its box eventually get separated.    It is far easier to find a missing IEC cord or its replacement, than it is to find a project specific wall wart.

[magic]

I spent a minute fooling around with the "charge pump" rail splitter.  Looks like it works!

https://www.tubecad.com/2018/02/blog0412.htm

What happens to peak to peak ripple magnitude (and output voltage symmetry ) when you replace all the diode networks with two half-bridge rectifiers and connect C3, C4 in parallel with C1, C2?