When finally be there one for all hobbyist desktop FormFactor ? - Page 1
Forum section: electronics / projects

author: unitedatoms
author_rank: Frequent Contributor
timestamp: January 11, 2020, 01:33:52 am
content: I mean when can I stop thinking about mechanical aspect of placing a 2D board into 3D real enclosure ? Similar to Eurocard standard, Music synthesizers tradition, or Kamak or LXI chassis or old PC style butsmaller, to fit on our shelfs and tables.I envision a shallow300 mm deephorizontal enclosure100 mm highand may be200..400 mm wide. With vertical slots populating a simple 50-100 pin backplane, and metal front panels with all the knobs, connectors, LEDs, buttons. It should have a variety of integer multiples of widths from say 20 mm to 100 mm. Well agreed upon pinout of backplane. Backplane can be just a flex flat cable based on IDC female connectors. And someone will sell plugin DIY kits for power supplies, control CPUs, USB, TCP bridges,screens with real bezels, etc.It should be available at 2 (or low 3) figure dollar costs per enclosure kit, or component or kit for building a slot member. Or barebone kit with ~20..40..60W power supply and choice of favorite controller with debugger and AC power cable included... When ?

author: james_s
author_rank: Super Contributor
timestamp: January 11, 2020, 01:38:56 am
content: For what type of projects? I don't think backplanes and plug-in modules are common anymore outside of certain areas like the modular synths you mention. Certainly most of my projects are a single PCB and maybe a power supply or display module in a box. I like the clamshell style desktop enclosures, Pac-Tec makes a series of them as well as other manufactures.What I wish is for the multitude of Chinese sellers offering enclosures and protoboards would get together and make boards that actually fit the enclosures with screw holes that line up with the bosses in many of the boxes.

author: mariush
author_rank: Super Contributor
timestamp: January 11, 2020, 01:45:53 am
content: I'd be fine with enclosures which can fit an ITX motherboard (170x170mm)I feel like it's time we move on from IDC headers though, and anything imperial (ex 0.1" pitch headers). Maybe we should move to 2mm or 2.5mm, or 0.5mm/1mm flex strips.The ITX reuses the atx standoffs, but the distance between center of holes is 132.08mm if my math is right, which should be close enough to 132mm.. just make the screw holes a bit bigger than unc 6/32 and maybe use m3 screws and standoffs and you'll have enough play to handle both.

author: unitedatoms
author_rank: Frequent Contributor
timestamp: January 11, 2020, 01:51:39 am
content: @james_s:I'd define this type of projects as "playground builds with chance of becoming permanently useful". Mostly for software/firmware minded people with no mechanical experience. Power supplies with digital or analog controls, acquisition boards, low cost lab test and measurement designs, may be somewhat non-demanding RF, or real RF with metal boxes placed on plugin boards and coax jumpers running from plugin to plugin on front panels, standalone or headless Spectrum analyzers, Scopes, CNC controllers etc. Anything bigger than single naked board or Arduino with one shield.Even for Arduino, those 20 or so pins can be reserved forever for Arduino to keep it acceptable as main controller if user prefers.@mariush:I am not mechanical experienced. I only have an instinct, that boards should have only one or two strong constraints for dimensions, not all 3. Say the thickness is between 1..2mm, height is always 100 mm. Length is anything up distance to front panel (0..300 mm). Eurocard allows a rigid inserts and crews for plugins. But it forces user to make design full sized. What If I only need 100x100 mm. Then my front panel (piece of metal with knobs) can have just wires in air reaching an edge of a board.

author: IDEngineer
author_rank: Super Contributor
timestamp: January 11, 2020, 02:05:10 am
content: "The nice thing about standards is that there are so many different ones to choose from."Or, in cartoon form:

author: unitedatoms
author_rank: Frequent Contributor
timestamp: January 11, 2020, 02:27:41 am
content: Quote from: IDEngineer on January 11, 2020, 02:05:10 amHa ha. I will try to list 14 standards to justify a need for 15th one.1. LXI … No thank you, I will keep my money for myself and sanity for a real job2. Desktop PC … No, it is shelf thing, should be small and I have no 8 projects to fill it, only 4 at most.3. 19 inch Rack … No, it is shelf and very shallow and narrow one. Also there is no that much money I am willing to spend on metal and shipping4. Arduino … No. Is it even a backplane ? How do you address the shields when you have more than one ?5. USB hub with star of cables … I already have it and I am not full time writing high level software or Signed Certified Device Drivers, thank you6. Kamak … Too high, it is named "Crate". I don't live in nuclear bunker next to particle accelerator7. GPIB … I can possibly build things that can fit inside this connector alone8. Eurocard … No, the backplane is rigid and pinout is taken for who knows what purposes, but I will take your aluminum profiles for panels with screws if sold for reasonable price.9. PC104 … No. It looks like very expensive Arduino10. PCI-Express … No, I am too old to learn FPGA and too poor to pay for identificators or whatever is there involved, I only need few bytes to bit bang11. Automotive Radio Formfactor … No. Too small to be a crate, too large for single project.12. Some random HP or Tektronix frame... No the formfactor is there, but size is unyieldy13. VME .. No. It is vertical and obscure14. Some other standard I am not aware about … No. Because that is exactly the reason: the fact that I am not aware bout this standard.Conclusion: need the standard number 15

author: DaJMasta
author_rank: Super Contributor
timestamp: January 11, 2020, 02:45:25 am
content: It sounds like you're describing a half width rack chassis or so? Maybe 2-3U high?Works great for larger products, and there are some chassis available in that sort of size, but big enough to be a little pricey and a bit heavy/large on the desk for a smaller project. Most of my stuff doesn't need nearly that much space, and 300mm deep is most of a shallower workbench.If you can keep the size in a 200mm cube and avoid needing to use the chassis for heat sinking, you could probably 3d print a chassis... may be the easiest way to deal with chassis these days, though you can get laser cut wood or acrylic to do larger/different looks pretty easily.

author: unitedatoms
author_rank: Frequent Contributor
timestamp: January 11, 2020, 02:53:38 am
content: Quote from: DaJMasta on January 11, 2020, 02:45:25 amGood keyword, but, half width rack is to fit into rack. I only need to fit plugins into enclosure, not enclosure into rack. But OK. I remember trying to look for half width rack stuff. It is not available in raw enclosure form, or I was not searching well enough. Anyway. If someone is selling a steel enclosure (3D print enclosure is fire hazard) withcompatiblefeatures for incremental population slot by slot, (available pieces of aluminum profiles, rails, brackets) I will like it a lot. Most of users do not have machine workshop, at best everyone has a drill and tap and screwdriver.B.T.W. I think the depth of instruments historically comes from CRT tubes. Those are gone. Now the 2D real estate is occupied by flat screens. But I don't see too many hobby projects using any reasonable screens. With no screens and the depth dimension being now free the obvious choice is vertical slots with plugins sliding-in horizontally.

author: DaJMasta
author_rank: Super Contributor
timestamp: January 11, 2020, 03:23:50 am
content: You say they are a fire hazard, but there's no concern unless you're using a fair bit of power or with very high voltages (or something else that needs the chassis shielding). If the temperature of the stuff in it gets hot enough to melt the plastic, yes it's not suitable, but at least most of my projects don't involve that kind of power consumption. There's also flame retardant plastics available, though they are not as common. Part of the problem with a universal chassis is that something like a bench power supply needs to be rugged and have some heat dissipation capability while something like a benchtop filter, amplifier, or some other piece of gear could probably fit into a much smaller case with no such power related requirements.I think a smaller aluminum chassis could be viable - but to some extent there is a supply of those out of China - but not in the benchtop form factor, really. There are some more bench-top options available, but they are $30+ each in my experience. It may actually be easier to find a commercially available metal box to house something else entirely - then the standard can just be how to arrange regularly sized things inside of it.

author: unitedatoms
author_rank: Frequent Contributor
timestamp: January 11, 2020, 03:38:27 am
content: Quote from: DaJMasta on January 11, 2020, 03:23:50 amAgree. The heat is a major concern. And it requires a metal, even at the x10 fold cost. And it requires a mechanical engineering talent.Another problem is thatnone, zeroof available metal enclosures have any features to mount PCBs. As if the designers have a goal to develop a passable shell, but only useable to store a bag of sand, not a PCB, transformers, plugins.

author: awallin
author_rank: Frequent Contributor
timestamp: January 11, 2020, 12:51:47 pm
content: Quote from: unitedatoms on January 11, 2020, 02:27:41 am15. CPCI-Shttps://en.wikipedia.org/wiki/CompactPCI_Serial(open hardware backplane there:https://ohwr.org/project/diot-crate-hw/wikis/home) - not sure what the connectors cost? hopefully not too much. They seem to use 220mm or 160mm deep cards, while 100mm would be nicer for small projects and racks.

author: Rerouter
author_rank: Super Contributor
timestamp: January 11, 2020, 01:17:17 pm
content: If you wanted to be a bit of a mad hatter, you could always grab a server drive shelf chassis and re purpose the hard drive sleds into slots for your equiptment, could even replace the backplane with your own