- Published: Monday, 19 September 2011
- Written by Jon Chandler
- Hits: 6031
I'm always on the lookout for low cost, nice looking enclosures. I'll present a method of easily making a custom enclosure that looks great on the bench or anyplace else in the house. I touched on this technique in my various comments on the TAP-20 Power Monitor - here I'll spell out the details. Enclosures of this type are perfect for projects using an LCD or LED display, and minimize the machining a panel requires.
A small wood box or frame and a plastic panel make a great enclosure. Clear or colored transparent plastic can be used so that an LCD or LED display or LED indicators can show through the panel with no cutouts required. Cutting nice openings can be a downfall, so this works well.
The first step is to find a box or frame of suitable dimensions for your planned application. A box with a back is great for "finished" projects where you don't need access to the internal circuit boards. For a dev system or projects under development, a frame with an open back allows access for cables, programming and changing things around.
While boxes and frames can be built, I've had good results recycling something from the thrift store or even buying something new at Target, Walmart or Ikea. Desirable features include being big enough to fit your project and having the sides thick enough to use mounting screws to hold the panel. Frames like the one shown below are used to display nic-knacks on the wall. A shadowbox picture frame might also be used if the glass is replaced by plastic.
The box above and the frame below were Goodwill finds - a dollar or two a piece. The back panel of the box above would be a good place to mount connectors bur keep in mind that the panel has to be unscrewed to access the boards inside.
The frame below is designed for wall mounting. Being open at the back, it's ideal for a dev system that may require frequent access. It's deeper than necessary but that makes it stable when it's on the bench.
It even has hardware for mounting to the wall.
The first step is an accurate measurement of the enclosure. Using my digital caliper (a recommended tool available for $20 or less), I measured the enclosure to be just over 7" on a side. I like to make the panel just slightly smaller than the box/frame dimensions so that I have a little leeway in positioning the panel without extending past the edges of the enclosure. In this case, I made the panel 7.00", about 0.04" smaller than the frame.
The next step is to plan the locations of your parts. In this case, I'm building the enclosure as a dev system to hold a 4x20 LCD display, a TAP-20-USB board and a TAP-28 board. Be sure to provide some clearance to the inside of the enclosure.
I've also included locations for 2 pairs of binding posts on 3/4" centers. I don't have any particular applications in mind yet, but these may be handy to have.
No matter how I'm going to machine the panel, my next step is to draw the panel at full size. I use Microsoft Visio which has a lot of flexibility but there are many programs that will work just as well. Google Sketchup might be a good choice. The key feature is that whatever program you use must allow accurate positioning and produce a true 1:1 print.
Show the locations of all the mounting holes, holes for switches, LEDs, connectors and holes for screwing the panel to the frame. I've positioned the panel mounting holes in the corners but this probably isn't the best choice if the corners are mitered. Holes on either side not quite at the corners would be better to prevent forcing the mitered corner apart. The mounting holes should be positioned so that that the screws are in the center of the wall thickness. For mounting boards, 4-40 or 3mm standoffs are the usual choice. A 1/8" or 3.2mm hole works well in either case.
I had the panel laser-machined, so the holes for the binding posts are flatted. If you're machining the panel by hand, this is probably not necessary - two smaller holes can be drilled side by side and filed to shape. To have the panel laser-machined, my local hackerspace needs a drawing in SVG (scalable vector graphics) format with the lines to be cut and nothing else. Until you're sure of your process, it's a good idea to include a 1"x1" square to the side of your panel so that proper scaling may be verified.
If the panel is going to be machined by hand, include centerlines for each hole location to aid in accurate drilling. A plastic panel can be scored and snapped or cut with a jig or bandsaw. When hand-machining, I tape the panel in-place and drill right through it. Drill the holes first, then cut to size so your drawing stays attached.
The photo below shows the laser-cut panel. Notice the smooth edge finish. I like making my panels this way as the holes are precisely where I planned them to be - which unfortunately isn't always where they should be!
To mount the boards and LCD display to the panel, standoffs work well. Either 3mm or 4/40 may be used but be consistent. I have purchased a purchased a several assortments of 3mm standoffs from Chinese vendors to get a variety of sizes.
The photo above shows the standoffs for mounting the LCD display. The length was selected to position the front of the LCD just clear of the panel. Note that standoffs are available in male-female (shown here) or female-female which would take a screw from either side.
This picture shows the LCD mounted with nuts.
Here are the standoffs for the TAP-20-USB board. Two standoffs are needed to get the necessary clearance of the LCD connector. This particular LCD comes with an attached cable and female SIP. The TAP-20 also have a female SIP, so a row of header pins allows them to mate at a height penalty. If the TAP-20 have been assembled specially for use with this display, I would have installed a male header instead of the female SIP. Note that there are only 3 spacers installed. The fourth hole was exactly where I positioned it - but not in the right location!
The TAP-20 board is secured with spacers in anticipation of expansion cards being installed at some point.
Here is the finished enclosure. The four small holes are for mounting a TAP-28 board. For a more finished look, a label could be installed with a cutout for the LCD display. Since this system is just for dev, holding the boards and display where they can be used, I won't be applying any overlay at this time.
A nice option if an LED display or some types of LCDs are to be used, a colored transparent plastic can be used for the panel. For laser cutting, another option is 1/8" thick birch plywood - of course a cutout would be needed for the display. The photo below shows the power monitor with a red translucent panel. It's masked on the back with adhesive film.
This method provides a nice looking enclosure at low cost. For less than a cheap metal box from Radio Shack, a unique, custom enclosure can be made.
Is it really cheap? This is the brown frame shown in this article.