Building a quality enclosure, particularly internal component mounting

[jmalcovitch]

This might be a very basic (and even stupid?) question, but need takes me into an unfamiliar area.  I must build a small Arduino appliance into a handheld enclosure, and the results must be reasonably professional looking.  I'll be building 8-10 units, and while I could be required to generate another handful I do not expect to build them again.  The project is based around Arduino Micro and uses USB output, a serial LCD, and 5 switches... three momentary and two persistent state.  One of the latter is a power switch, the other is an input switch.

I've been researching various aspects of building a project in a good-looking enclosure -- my projects have historically been a pile of wires on a piece of plywood -- and have done the following:
- selected an enclosure with 9v battery bay
- arranged with a machine shop to do whatever I need to it
- found an inexpensive source for a graphic overlay, providing a clear viewing window for the LCD

What I have not found is any resource or information about how to effectively mount the components in this situation.  The enclosure has mounting bosses (terminology?) on both the top and bottom halves.  I assume a few things:

1 - that I want to fabricate a piece of perf board that screws to the top's bosses, and mount my LCD, switches, and Micro to this board
2 - that the Micro mounts near an edge such that its micro USB connector pokes through a matching hole in the front or side of the enclosure
3 - that I use tactile switches on the perf board below matching holes in the top, and there's some sort of plunger that floats above them

Of particular concern is that the LCD (standard 1602A) is thicker than the mounting bosses are tall.  If my enclosure hole is the size of the viewable area, I need to space the perf board off the bosses to create additional clearance.  Is it preferable to machine the case such that the bezel also protrudes through the case top?  I have not checked thickness of the case front to see if it ends up flush or not.

I would greatly appreciate any feedback on my circumstance, plus any pointers to reference materials on the internet or in print covering these issues.  Also very interested in thoughts on what switches and/or plunger things, since I've never used tactile switches and have no familiarity beyond their existence.

My immense thanks in advance for any help!
Jason

[rollatorwieltje]

Try to find one of those chip-on-glass LCD modules, that saves a lot of height. These EA DOG modules for example are Hitachi compatible and very flat.

[jmalcovitch]

Thanks for your thoughts on the LCD height issue.  I'll look into a lower-profile unit as you suggest!

Anyone with switch information?  Does one use such "plungers," and if so what are they actually called (or in which category to they live at Mouser)?

[rollatorwieltje]

There are tactile buttons with caps on them, so you only need to make the right size hole in the front panel, like these from sparkfun. Hole size and alignment is very important though. A bit of space is needed around the button, but not too much otherwise the shaft will tilt and the button won't register properly (or actually destroy the switch internals).

Another possibility is a foil front with tactile dome buttons. I haven't used those personally, but at work they are used quite often. Not sure how expensive that is. I would avoid those if you need to press the button often or when timing is important, they generally feel quite nasty.

[peter.mitchell]

I use... I can't remember the name but they used to be used on computers for power and reset switches,  they're 5.8mm x 5.8mm 6 pin through hole.  They have a keyed actuator so you can easily put caps on them,  and the actuator rod is keyed into the switch housing so it has very little play compared to standard tact switches.

For the LCD,  if you can't find one thin enough,  could you route a hole in a PCB,  mount the LCD on the underside and mount it like that?

[ivan747]

This has helped me a lot:


Oh, and Newhaven Displays make really nice, thin Chip On Glass (COG) displays. They come in parallel, I2C or a weird SPI-like interface, are very very small and the backlight is good. The viewing angle is average, better than typical character LCDs.

http://www.newhavendisplay.com/lcd-chiponglass-character-cog-c-3_111.html

I have used this one:
http://www.newhavendisplay.com/nhdc0216cizfswfbw3v3-p-2930.html

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Also this:
https://www.eevblog.com/forum/manufacture/electronic-enclosuremachining-supplier-list

[jmalcovitch]

My thanks for the information!  rollatorwieltje, that switch pointer is very helpful.  Peter, I have been contemplating that.  I'm reasonably certain that routing the PCB so the components on the back of the LCD drop through and the mounting holes sit flush on the PCB will deliver a nice fit.  I hadn't considered moving from that standard el cheapo display to something that better fits my needs, but one of the Newhaven units (or some other manufacturer) might be quite a lot better.  If I switch to a 12x2 I can orient it in the case the way I'd like, while the 16x2 forces the case to landscape orientation.  I had actually seen that video, Ivan, and it's a great idea.  For this project, my parts must all be on the large side... it's a handheld device for interaction by the holder.

If there are any additional resources related to my questions, I would certainly appreciate pointers.  You folks have, however, really come through to set me on a productive path!

Thanks,
Jason