Scratch building projects can be very satisfying. However I see two things as deterrents to us average hams.
Getting started on the project, and making it look good when its finished. If you’re an above average ham, read no further (you know who you are).
Getting a Project Started
I’ve become a fan of the Manhattan style of building from scratch. Nothing seems to get me started on a project as quickly as gluing a few pads and melting some solder. The actual gluing process has been described in print often, but how does one decide where to put them? There are many ways, here’s mine..
I like to pick the enclosure first, that’s right, before building the board.. This may seem like getting the cart before the horse , but this allows me to place it on a piece of paper and trace a line around the bottom, outlining the amount of space in which the board must fit.. Then by referring to the schematic, pads and components can be sketched on the board outline. (Fig 1). It won’t look beautiful but it will get you started. One of my favorite sayings is “Getting started is half done”. Besides, beauty is in the eye of the beholder.
Once the layout with the pad locations is finalized, cut around the outline of the enclosure bottom, allowing for wall thickness. This will become the dimensions of your board. Then punch holes in the centers of the pad locations with a pin. I use a bulletin board style straight pin with the little plastic gripper button. Place what has now become a template (Fig 2) over the board and mark the pad locations with a fine point marker. Then trace around the outline and cut out the board and glue your pads on the marks. The board is now sized for your chosen enclosure and the pads are glued. You’re already “half done” - quick and easy... From this point on, it’s place and solder the parts, but you have used an organized approach which will speed up the whole building process..
Nothing finishes off a good homebrew project like a good label. My step by step process is pretty simple, but works for me. Some of this information was presented last April at OzarkCon, and some of our local club members have duplicated it successfully. See Fig 3, for some typical labels made using this process..
First you’ll need some Tools of the Trade..(Fig 4). Software is very useful but not absolutely necessary. Manual printing, calligraphy, label makers, and typed labels are all useful here. Having said that, I have to say that I use Microsoft Publisher. It makes all the shapes I need, and has very accurate vertical and horizontal scales. If you draw a 2”x2” square on the monitor, when it’s printed it will be 2”x2” on the paper. That transfer of accuracy to the printed page is a very important requirement of any software you might use.
The first step is to draw a rectangle the same size as the front panel of your enclosure. Then print it out and doodle around (in pencil) with the placement of switches, leds, knobs, jacks, etc. Just rough it in so as to get some idea as to what you want the panel to look like. (Fig 5) Do the same for the rear panel, locating any power cord grommets, switches, fuses, etc.
Then make up the final label. Make sure to account for not only the centers of pot, led, switch holes – but also the diameters of the knobs, leds, etc.. I also use a copy of the final label as a drilling template to mark hole locations on the face of the enclosure. The procedure is the same as the one used to locate Manhattan pads noted above, punch with a pin and mark through the hole with a fine tip marker.
After drilling or punching the front panel of the enclosure, print out another copy of the final label. This one we’ll finish off and apply to the face of the enclosure Cover the face side with clear shelf contact paper to protect the printing. Strip off the protective cover and make a bow in the film when you place it on the label. (Fig 6) Smooth it down working from the center out so as to avoid air bubbles. Don’t cut it out of the paper yet. I print the final label on yellow paper, plain white seems pretty plain to me. Use a color you like, it adds some pizzazz to your project.
Next apply double stick tape to the backside in as many strips as necessary to cover the whole backside. I use 1.5" wide tape. Just butt the strips against each other running in the long direction. Some of my labels have had 3 strips on them. Don’t worry too much about the joints between the strips, they wont show through. You may want to get them a little closer than the one in the picture (Fig 7) , but even it looked fine from the top. I use tape sold as carpet tape, and it works very well for this application. It’s thin and has a fairly high tack so the labels stay put. In fast they’re quite difficult to remove up after they’ve been applied.
Turn the label over and cut the whole sandwich out, carefully. I like to go fairly slow with sharp scissors, and use strong lighting. Especially go slow around the radii...The older I get, the stronger the lighting requirement. The trick is to cut as smoothly as possible along the outside edge of the border.
After cutting, I pass a marker around the edge of the label sandwich (Fig 8) Use a color that matches the color of the enclosure, and the border. I attribute this great tip to Chuck Carpenter, W5USJ (QQ Fall 2003 p 18) and George Baker, W5YR (SK). My favorite colors are black enclosure, yellow label, black text and black outline, so I color the edges with a black Sharpie. If you have different color enclosure, color the border and edge to match it. The edges of the label will disappear, and when you look at the front you see the sharp printed inside edge of the border, minor outside edge imperfections won’t show..
Next is a critical step, but its not difficult at all. Attach 2 pieces of “magic” tape to the top edge of the label. Position the label on the enclosure panel, holding it firmly in place with your thumbs while smoothing the tape over the edge of the panel with your index fingers (Fig 9).These will be hinges to maintain the position while attaching the double stick tape. Lift the label up and remove the protective covering from one of the carpet tape strips. (Fig 10) Lay it back down, smoothing from the center out, sticking the label down. Remove the 2 pieces of “magic” tape (hinges) and then stick down the remaining part of the label. (Fig 11) There, you're nearly done! It takes more time to read this than it will to do it after you’ve had some experience with a few. Try it out on 1 or 2 samples before tackling a real panel. Just stick 'em down on a piece of cardboard for practice.
We still have to mount the components on the panel. I use the hobby knife with the triangular blade to cut out the little disks of label material in the component holes. A sawing action from the front of the panel works best here. When I install the pots, switches, LEDs, etc., I tighten them from the backside of the panel, that prevents the clear covering from wrinkling. I ground some small open end wrenches thin for just this purpose. A trick to use for tightening BNC and RCA phono jacks is to first finger tighten the jack Then install the plug on the front, and grip it with a pair of pliers while tightening up the nut on the backside. This allows you to tighten it nice and snug without scarring the exposed part of the jack.
In Conclusion Installing a project in an enclosure was the least enjoyable part of a project for me. I far more enjoyed building the printed circuit boards. However that pretty much limited me to building kits, or doing my own boards, which I viewed as too time consuming and less successful than I care to admit...
Now I can build from a schematic fairly quickly using Manhattan pads, look forward to installing the board in an enclosure, and making a good looking label to put the finishing touches on it.
I hope you will find these tips to be useful in your building process, from the schematic to a great looking finished project.
This article appeared in QRP Quarterly Magazine, Summer 2005
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