Way to mount custom pcb/perfboards/arduinos to a NEMA cabinet? - Page 1
Forum section: electronics / projects

author: Red Squirrel
author_rank: Super Contributor
timestamp: December 13, 2014, 02:58:22 am
content: I am redesigning my home environmental system, which currently consists of a DIN rail as cross connect and power distribution going to individual relay controller and an arduino sitting in a little plastic case on a rack shelf. Really it would be more efficient to have that all neat and tidy inside a nema enclosure separate from the server rack. I'm just not sure what is the best way to mount the PCBs. I would have one or more arduino, some circuit board for relays/terminals and most likely a raspberry PI to act as the server to communicate with the arduino(s). What is the best way to mount the PCBs, would something like these be adequate?http://www.ebay.ca/itm/100PCS-3mm-Mounting-Hole-Nylon-PCB-Supports-Spacers-Tension-Type-Standoff-8mm-/390991127817?pt=LH_DefaultDomain_0&hash=item5b08e32509Or is there a better way? This would be in a metal cabinet. I don't have special tools to make threaded holes to use threaded type standoffs though, otherwise I'd use that.

author: SeanB
author_rank: Super Contributor
timestamp: December 13, 2014, 06:00:58 am
content: You get empty DIN rail clippable cases that have screw terminals as part of the moulding for DIY equipment. Otherwise a regular case and some plastic clips to hold the board, as used in most consumer equipment like VCR and DVD players.

author: calexanian
author_rank: Super Contributor
timestamp: December 13, 2014, 06:22:16 am
content: Most NEMA 4 or IP 66/67 style boxes will have mounting bosses inside them to either allow direct mounting of a DIN rail system, or are offered with a backplate that can be drilled as needed for mounting anything. I like the BUD NBF series enclosures. Hinged lids with nice latches and available with either opaque or clear material and for a small extra cost outdoor versions can be had. They have every rating under the sun available.

author: Red Squirrel
author_rank: Super Contributor
timestamp: December 13, 2014, 06:04:41 pm
content: Don't have access to a 3D printer, but never thought of epoxy, would it hold up strong enough if I was to epoxy nuts in place and then screw in regular metal standoffs? Ex: would it fall over time or pretty much be a permanent bond? Then I can screw the standoffs in the nuts and then screw the pcb in. There's all sorts of neat standoffs/extenders on ebay too, might even experiment with pcb stacking to save on space. The enclosure I have does not have any special mounts as mentioned or anything like that. I had trouble even finding one. Digikey sells them but they get expensive fast as you move to larger ones or go with ratings other than 1. I probably wont have a din rail in it but might have one outside. That, or a bix block for cross connecting. The cabinet may also act as a prototype for a potential project so figured it be easier to leave the cross connecting to the user as environments vary. Technically you can just wire everything in directly. (there will be screw terminals on all the circuit boards)I could put the nuts on the back of the case too but it will make mounting the actual cabinet to the wall a bit harder as it wont be flush, and if it gets loose it would be hard to tighten.But yeah think I'll go with the epoxy idea, seems like the easiest and no need to drill holes in the cabinet.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: December 13, 2014, 06:29:39 pm
content: DIN Rail Arduinohttp://www.industruino.com/DIN Rail RasPi casehttps://www.modmypi.com/din-rail-raspberry-pi-caseThere are plenty of other DIN-rail mounting cases for various shapes & sizes from Camden, Phoenix & others

author: ajb
author_rank: Super Contributor
timestamp: December 13, 2014, 08:39:09 pm
content: I'd be really wary of trying to epoxy a nut into an enclosure, especially if that enclosure is subject to substantial temperature changes. A basic tap and drill set can be had pretty inexpensively in metric or imperial sizes.If you can afford to lose a bit of depth in your enclosure, a back plate is definitely the way to go, especially if you're not using DIN rail. Mount four standoffs in you enclosure (if it doesn't already have bosses), and then you can make whatever threaded or unthreaded holes in the back plate you need for mounting your components without compromising the NEMA/IP rating of the enclosure. You can also attach all of your components and do all of your internal wiring on the backplate before it goes into the enclosure.

author: Red Squirrel
author_rank: Super Contributor
timestamp: December 13, 2014, 09:34:09 pm
content: Ended up ordering the following:http://www.ebay.ca/itm/181505967000http://www.ebay.ca/itm/221558620505http://www.ebay.ca/itm/330884050679Funny how shipping stuff from China is so much cheaper than shipping stuff from the states too. The DIN stuff sounds really cool though but that's rather specialized and probably quite expensive to implement by the time I'd get that shipped and so on.Think what I'll do is drill it and epoxy the nut on the back. At least I still have a mechanical connection so if the epoxy was to fail it would just make the standoff loose and not actually cause it to fail. It's not like this is something that will get unscrewed/screwed very often, just need to be able to in case I blow a board or need to do a modification or something. Only thing the arduino boards really don't have much clearance near the mount holes so I might have to get creative with those but I'll see for sure once the standoffs and other hardware arrives.Actually backplate would not be a bad idea and I can probably afford to loose a bit of depth (did not buy backup battery yet so I can size it accordingly after). What would be the best thing to use as a backplate? Something I can find at a hardware store preferably. I'm thinking some kind of sheet metal like for ductwork or something.

author: ajb
author_rank: Super Contributor
timestamp: December 13, 2014, 10:09:29 pm
content: If the enclosure is reasonably small (say, less than 12"x18"), I'd probably go for 1/16" 6061 aluminum. It's easy to cut or drill and is thick enough to tap. You could get away with 1/8" or 1/4" acrylic, too, as long as you don't mind something non-metallic. If the enclosure is larger, or if you're mounting particularly deep and heavy components to it, I'd probably go up to 1/8" aluminum.You might be able to find the aluminum at a local hardware store, or order it fromMcMaster. Big Box stores will likely have acrylic, but maybe not as thick as 1/*" or 1/4".

author: Red Squirrel
author_rank: Super Contributor
timestamp: December 13, 2014, 10:16:23 pm
content: It's just a 10x10x4 so not too big. I wanted something bigger but could not find any without paying near or even over 100 bucks so I'll have to be creative and fit all my stuff in there. I'll do the cross connects outside of it as that actually takes the most space. I think I recall seeing fairly thick aluminium panels at Home Depot so I'll have to check that out closer. Never heard of a die and tap before and just googled it, looks interesting, might look at buying one and doing my own threaded holes after all.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: December 14, 2014, 03:19:22 am
content: The few cabinets I've seen with DIN rails all had aluminum backplates on standoffs and you used self-tapping screws to attach your gizmoes to the plate.

author: calzap
author_rank: Frequent Contributor
timestamp: December 15, 2014, 02:35:00 am
content: For sheet metal that is thick enough to tap, I use a Klein multi-tap. See the pic. The tip is reversible, and the other end has an additional three taps, making 6 in all. Klein also makes one with only three taps It works great in mild steel, aluminum, and some plastics. Use a drop of cutting oil on it each time. I'd be hesitant to try it in stainless steel. Very common tool used by electricians in the US. Don't know if it's available in metric. Klein's website iswww.kleintools.com.Mike in California