Small enclosures - Page 1
Forum section: electronics / general

author: soldar
author_rank: Super Contributor
timestamp: September 20, 2019, 06:47:55 pm
content: I was just dismantling a project/device I built about 40 years ago and i realize I built it unacceptably dangerous. In a metal, ungrounded enclosure, 230 Vac all over the place, way too close to metal and other electronics. It should never have been built like that.When I started out I sometimes used rectangular metal food cans but I don't think I've seen any in a while.I used to buy aluminum ready-made boxes and also make my own with aluminum sheet which is easy to bend and work.These days when I build something like a 230 Vac triac power control I sometimes end up putting it in a wooden box because it is what I can build quickly with what I have at hand. One negative aspect of wood compared with metal is heat dissipation.Today if I build or use a metal enclosure itwillbe grounded no matter what but grounding means thicker cable and Schucko plug so sometimes I would prefer to not use metal enclosure.I have made some with one half wood and the other half metal. that works out pretty well. You know, the type with two halves shaped like a U, the bottom holds two sides and the top the other two sides. It is easy to built the bottom of wood and then hold the metal top with screws. I think at this point this is the system I find most efficient. Some sheet metal, some wood and it is very straightforward.I have also made some enclosures with PVC but it is a lot of work. Still doable though. I would take a length of PVC sewer pipe, cut it lengthwise, flatten it and then cut and fold as necessary. A lot of work for mediocre results.I know there are enclosures sold commercially but they seem too expensive for what they are. It is one thing if I am building a nice lab instrument like a PSU but if all I need is any box to house a small circuit I do not want to spend on the enclosure more than on the circuit.So this makes me think that there should be products sold in plastic boxes that could be later used as enclosures for electronics but I can't think of any. Can you think of any?Any other ideas?I am surprised that some products like pastries and cookies are still sold in tin cans and not plastic. On the other hand, any plastic food enclosures are too thin to hold anything.I guess commercially sold enclosures begin to look not so expensive.I'd like to hear your thoughts.

author: Kilrah
author_rank: Unknown
timestamp: September 20, 2019, 08:44:46 pm
content: The usual large component distributors have loads of cases, I've been using quite a few of them for some projects. They were in the $10-15 range, so hardly expensive.But nowadays I custom design and 3D print, so much nicer.

author: Richard Crowley
author_rank: Super Contributor
timestamp: September 20, 2019, 09:11:56 pm
content: I like using aluminum extrusions. Mainly U-shape channels.I use them for the sides of the box, typically 1.75 inch tall (1 rack-unit).And then a sheet of metal (or plastic or wood) as the top and bottom.It is easy enough to glue a piece of aluminum foil inside the top and bottom if you need a fully-shielded enclosure.My go-to source of extrusions is:https://www.orangealuminum.com/bar-stock/channels.htmlAnd they have a growing variety of other specialty Al extrusion stock.

author: KL27x
author_rank: Super Contributor
timestamp: September 20, 2019, 10:10:18 pm
content: QuoteLast mains circuitry I needed to enclose was a small transformer, mains socket, output socket, and a switch. I used the screw top plastic jar my shaving cream comes in. It's thick plastic, not like a peanut butter jar or cheap sandwich container. It's basic cheap stuff. Taylor of Old Bond Street. Good lather without being too fatty/oily and the fragrance is subtle.If you are already initiated to a shaving brush, this isn't the normal hard shaving soap in a bowl. It's a cream. If you tried to lather your brush directly in the bowl, you'd just make a mess of the whole thing, and you'd withdraw enough product on your brush to shave 3 gorillas. Takes just a dab on the brush, then lather it in your stainless steel shaving bowl. According to my purchase history, a container lasts me about 6 months. So there's a couple enclosures a year.

author: Red Squirrel
author_rank: Super Contributor
timestamp: September 21, 2019, 02:48:55 am
content: This is kind of niche but when I bought my 24 bay HDD enclosure it came with a bunch of "dummy" drives that were basically a plastic container the size of a hard drive with no top. I would drill 4 holes and put long bolts in it and then use a plywood cover.Pardon the crudity of that, it's an old project... but it's still in service! Runs my HVAC.For a more common option, tupperware containers might be one way to go, they are decently cheap and come in various sizes.As a side note, how concerned should one be about fire if using wood? I want to move towards building my own enclosures for server/computer stuff because rackmount cases are so expensive and selection is slim, so I want to just build my own so I can come up with a design and be consistent. My train of thought is even a catastrophic electronics failure is not going to burn long enough to actually ignite solid flat wood but not sure if I'm right. Ex: try starting a camp fire by holding a lighter to a 2x4 it's kinda hard to get it to ignite.

author: soldar
author_rank: Super Contributor
timestamp: September 21, 2019, 11:46:20 am
content: I used to buy 1.0 and 1.5 mm aluminum sheet and make boxes to my own measurements. I still have some sheet around. They worked but I never really finished them nicely so the results were always kind of rough.I have used Tupperware-type containers for very specific occasions but I do not consider them really suitable. For example, I was a a boat with a 24 Vdc system and had to rig a voltage reducer for my 12 V computer. Because I just needed a temporary, quick and dirty solution, I took a Tupperware container, cut some holes for the wiring and the circuit was just placed inside. (BTW, some days later someone told me the thing, placed in a locker, was smoking. I disconnected it and never said a word to anyone. A fire is the last thing you need on a boat and we were supposed to be extremely vigilant. I don't remember if there was something wrong or just lack of needed heat dissipation.)But I do not consider Tupperwares rigid enough or suitable as a permanent solution. The one advantage they do have is they are watertight and I have used them a lot just to keep things while on boats.Regarding wood, I use it but it is probably not allowed by codes for permanent 120/230 V mains connections. I suppose arcing for a while could start a fire so I just make sure my connections are doubleplusgood. I cannot see any danger in using wood for enclosing low power electronics. Radio and TV cabinets were made with wood and there was much more danger of getting a fire inside.I guess it would not be difficult to line the interior of a wooden box with sheet of steel or aluminum. That should protect against fire pretty well. Aluminum foil would be effective for EM emissions but probably not for fire. Probably 0.2 mm steel or 0.5 aluminum should be enough.I have often had cardboard boxes which were very adequate in shape and sturdiness but I just do not see cardboard as suitable material. I thought a coating of epoxy or something similar might make a good enclosure but I have never tried it.Spending $15 on an enclosure that will house something substantial is more than justified. OTOH, I find myself now trying to get the small mains transformer, diode bridge and capacitor out of the main box and into a box of its own. It is not worth spending almost anything because I can but the entire wall wart for under $5 ... in fact, I can get it for nothing from my junk crate.Ha, I just remembered that for this type of project I have used in the past Twinings tea cans. Decades ago I built a power supply for a girlfriend's audio player in the kitchen and she loved the can could just go among the rest of the tea cans, unnoticed. I remember the opening at the top is narrower and it took some work to get everything inside. I guess I could cut out the bottom if needed. I know I have some of those cans around ... somewhere.One thing I am always extremely careful about is making sure cables are protected from friction and chafing where they enter by rubber grommets or thimbles.