Both the creators of hobby projects and the creators of professional prototypes share a common problem -- what to do about the cabinet. In the not-so-distant past, creating a prototype printed circuit board (PCB) was the most time-consuming and expensive problem, but now this is much less of an issue. By comparison, acquiring an affordable, professional-looking cabinet remains an expensive undertaking.
Recently, I've been chatting to someone who thinks he has a solution -- EETimes community member Charles Spence. In a recent telephone conversation, Charles was saying that he is thinking of launching a Kickstarter project, but first he would like to "hoist his idea up the flagpole and see how well it flies," as it were, and that's where you come into the picture.
I personally really like Charles's idea, so I asked him to write it up in more detail so I could share it with you. Charles responded as follows:
Dear Max, thank you for giving me the opportunity to share my idea with other members of the EETimes Community. One part of building prototype electronics that continues to plague me is the cabinet. It still seems to be the remaining piece for the hobbyist and professional that forces their work to look amateurish to family and friends or to the customer. While I admire the quick and dirty methods Jim Williams and Bob Pease taught us, only the enlightened few seemed to deeply appreciate the ingenuity of a cookie tin for EMI shielding. However, it takes an understanding wife or boss to accommodate the hoarding of these likely Christmas gifts.
While I am also a fan of the "dead bug" method of circuit prototyping, it tends to hide significant issues with regard to parasitic capacitance or leakage paths that -- if you ever want to replicate your circuit -- will bite you. I also argue that creating a decent cabinet is more time-consuming than creating a prototype PCB. This is because you can go straight to a PCB for little relative cost these days (when I started my first real electronics job, it was $1K for a set of two-layer proto-PCBs; now it's only around $120 on the high end). I create a PCB for all my prototypes -- what seems to remain is the box.
On my last project, I think I came up with a solution I would like to share with your readers. This solution applies principles similar to those that enable low-cost prototype PCBs and even low-cost integrated circuits -- share the panel or wafer.
Current industrial CNC laser cutters can slice up a panel of aluminum quickly and cheaply. What seems to plague the sheet metal business is making a bend cheaply enough for use in prototype cabinets. A simple aluminum extrusion gets past this issue, which inspired the following cabinet design.
This example represents a 3" x 5" x 7" deep cabinet. The panels are intended to be cut from 0.050" thick 5052-H32 sheet aluminum. For the purposes of this example, the extrusions are shown in orange in an effort to make their design more visible. These extrusions are intended to be made from 6061 aluminum hardened to T5 or T6. The extrusions do include a guide channel for a PCB, but the PCB(s) could also be mounted to any panel via standoffs and screws.
In one implementation, the bottom and two side panels could be glued to the extrusions with a cyanoacrylate (Krazy Glue I) like Loctite 380 (Black Max) or an adhesive transfer tape like 3M 465 or 966. The top panel would still be allowed to slide to facilitate easier access to the internal electronics for debugging and testing.
The cheapest way to make this type of cabinet uses raw aluminum. My current estimates show they could be made with custom cutouts for $50 each in quantities of one, assuming several people ordered cabinets at the same time (each cabinet can be different). Furthermore, since the un-assembled cabinet can be shipped flat, it can be sent via USPS Priority Mail bubble pack to most places in the US for less than $6.00.
Observe that this basic design can be extended all the way up to 19" rack-mount cabinets. The front panel can be extended to have rack mounting holes (but it would also need to be made from thicker aluminum, which would drive the price up a bit). A simple bracket could be mounted in the middle to stiffen the center section for cabinets this wide.
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