K0FF's Homebrew Tips
Home construction practices- EWBs-Home Made Circuit Boards
or Everything that is OLD is NEW Again!
Hello and welcome to another installment of K0FF's Homebrew Tips.
I've been very busy since my last installment tinkering with all kinds of circuits and antennas. My Square Loop (Sloop) copper dipoles for 10, 6 and 2 meters have taken off and been a worldwide hit. A QST article by another author won the Cover of the Year award (remember you saw them on eHam first!). There has been a renewed interest in antenna homebrewing using copper and plastic plumbing parts worldwide, and *IF* I was a small part of encouraging that, I'm happy for it.
Search the Internet for "GEO>K0FF" or George Dowell or just K0FF to see many more of my articles, rig mods and homebrewing tips, the majority of which I intend to update and publish right here on eHam in the near future. Most of my musings concern the methods of making electronics projects for radio and other hobby interests. We will eventually discuss panel layout and artwork, transformer winding, antenna construction ideas, metalwork in the home shop with simple hand tools> shearing, drilling, punching, tapping, bending, measuring, layout, etc. and any other related subjects that reader's request. Toady I want to tackle the most important aspect of ANY electronic project, the Wiring Board.
Since the earliest days of radio, we HAMS have always been circuit tinkerers, starting with solid state (the diode detector), devolving to hollow state (tubes) for a period and then back to solid state again (the 3 legged diode or * transistor *). No matter what kind of components, we always needed a chassis of some kind and wires to interconnect those components. Originally we used mom's breadboard and tacks, advanced to metal chassis and wires, through plastic boxes with PCBs. In my youth, most of my circuits were built up on cardboard boxes with pinholes for the wires and components. Only an important project deserved a metal chassis and I made (and still do) those myself.
I love to play around with transistors, resistors, capacitors and all of the other discrete components, learning long ago from Wayne Green's 73 Magazine articles that any circuit no matter how complicated looking is just a bunch of individual stages, hooked together with coupling capacitors, transformers or other means, sharing a common power supply.
Circuit Boards also referred to as PWB (Printed Wiring Boards) and PCBs (Printed Circuit Boards) are at once a boon and a bane to home construction. We tend to think of PWBs as a child of modern electronics, specifically the transistor and IC era. Actually PWBs were in use for tube circuits too, and many early post WW2 home radios used them to simplify assembly of the famous "All American 5" 5 tube AM radios. Long before even this application, fiber and phenolic boards found their way into WW2 radios in the form of terminal boards, onto which individual components were wired into "modules" for ease of manufacture and physical stability. Anyone who has looked inside an old Army radio has probably seen one or more of these long strips with terminals pressed down each edge in rows and resistors and capacitors wired between the terminals.
Today's compact solid state circuitry would be nearly impossible without some form of PWB, and current production items are relying more and more on leadless, surface mounted componentry with multiple layer PWBs. .
Since a production item is mass produced for the consumer, it is obvious that this type of rigid construction is imperative, especially considering that most PWBs are actually assembled by robots in a big factory by unskilled workers.
Home construction of any well- researched circuit design will also benefit from a traditional PWB as the "homebrewing" becomes simply a copy of the original, and to me nothing but a soldering exercise ( ala Heathkit).
Don't get me wrong, I love kits, especially Heathkit. The builder learns a lot from a well written assembly manual. Often my leisure reading consists of browsing the THEORY section of an old Heathkit manual.
Kitbuilding and HOMEBREWING are different pursuits though and this article addresses a simple way to create a perfectly functional circuit board from inexpensive parts without the need for photo etching, artwork and chemicals. There are other approaches to this problem, each has its own merits, but this approach has some singular advantages when it comes to reproducibility, stability, good looks and extreme accommodation of experimenting in regard to circuit values and modifications.
True homebrewing is an evolutionary process as you start out with a vague idea or design and try different components; add stages together and eventually come up with something that works for the intended purpose. The old saying of "First make it work, then make it pretty" still applies.
While it is certainly possible to make etched copper clad boards at home, the effort to me at least winds up being more about making the circuit board than making the circuit. Any changes results in a botched looking project, usually needing a board redesign and days worth of time lost. Simply buying a circuit board from a supplier for a particular project still leaves you lock step in with the rigid original design with little room for individualization.
FIGURE 3- Home Made Etched Boards
This whole process has actually stymied my love of homebrewing for many years, yet I was not ready to go back to the point-to-point wiring of simpler days. For one reason, no matter how cautious I was it never looked as neat and orderly as a PCB version. "Dead Bug" construction got its name for a good reason; it looks like a bunch of dead bugs. Ironically from an RF standpoint the short lead length fostered by Dead Bug is a distinct advantage!
FIGURE 4- Home Made Dead Bug Construction- Surface Mount QRP TX
Presented here is a hybrid approach to WBs or Wiring Boards, an old idea revisited with modern techniques applied.
I call it K0FF's Eyelet Wiring Boards (EWB), and certainly I can't take credit for their invention, but just as with my Copper Antennas, I hope to be responsible for their rebirth.
K0FF's EWB Eyelet Wiring Boards.
Observing all the different wiring methods of today as well as the past, a scheme was devised that would provide a simple, flexible and stable platform for homebrewing electronic circuits at home. Focus was heavy on the adaptability of the layout and ruggedness required for experimental changes, which might require unsoldering components many times during the research stage. One a final layout is determined, it is desired to be able to duplicate the Wiring Board with ease, be inexpensive, and be able to communicate the construction process to others in an article for their use. Time of construction of the WB was to be minimal, use common tools, and to repeat, it had to be cheap.
In a nutshell, we are taking a glass-epoxy or other material BLANK, BARE PANEL, no copper, drilling holes in the appropriate places and installing tin-plated BRASS EYELETS for the connection points. Sound simple? Well it is, but this simple trick has renewed my interest in homebrewing overnight. It is fast, cheapo and FUN! I can turn out 50 1" by 2" EWBs with 21 holes in an hour, for pennies.
FIGURE 5- K0FF's EWBs
First we start by ordering a quantity of fiberglass circuit board material, sans the copper clad. Many eBay sellers will etch the copper off for you and send you the bare, naked board material. I get it in 6 inch by one foot panels, but any size can be had up to 24 inches square at least. Most of my projects are made on fairly small boards, one by two inches being the most common, but three by five inches finding a lot of use too. In many cases, the enclosure dimensions determine the final size. For moderately large reproduction of a single design, large panels are used during the drilling stages and then sheared to size before the eyelets are installed. Primarily I use the .060" G-10 or FR-4 material because scraps are ubiquitous and cheap.
FIGURE 6- Blank-Bare Board Material
Laying out the pattern of holes:
Layout can follow traditional PCB type designs and clones of existing boards are easy.
Try making a Xerox copy of an original board, and then lay the paper copy on a blank panel, mark the hole spots with a stylus or needle. Drill the first panel as the template master using a tiny drill bit, from this many copies can be made and changes can be incorporated.
Layout is facilitated if some common conventions are followed, such as using a 1/10" grid as the skeleton for the design. Xerox copies of PERFBOARDS can give a nice geometric pattern to help get your holes all lined up the way they need to be.
FIGURE 7-TEMPLATE layout on paper
FIGURE 8- Template, Drilled board stack, individual boards sheared from panel.
Once a design is developed, individual holes will bear their GRID COORDINATES so that they can be easily located when transmitting the design to others using email and pictures. Notice how this project kit I make refers to the individual holes simply by a consecutive numbering system.
FIGURE 9- Speak2me kit
For an original design or improvement of an original PCB, they layout can often be compacted by about one-half by altering the construction methods. This simply involves placing more than one component lead into a single eyelet. By treating the eyelet as a circuit node, most or all of the component leads that are electrically tied together can be inserted into a single eyelet. When the number of leads gets too large for a single eyelet to accommodate, such as a ground or power buss, a string of them are mounted in a line and electrically tied together with fine wire. When distant eyelets need to be connected together, I use fine wire, insulated with clear Teflon tubing or sometimes a Zero-Ohm resistor.
Same circuit three different concepts. Original as manufactured by a big company, direct EWB clone and Optimized EWB version. Optimized version shrinks whole board to 1 in square without cramping!
FIGURE 10-Traditional PCB Vs. EWB style layout
Use of a drilling template simplifies reproduction, with a drill press being the only machine tool needed. For one off EWBs a simple hand drill or Dremel will suffice, and a manual mechanical drill is perfectly fine too. For last minute hole additions, I keep a drill bit in an old radio knob on the bench to hand drill a spot hole in just a few seconds. Making a tiny pilot hole with a high-speed hand tool like a Dremel makes it easier
FIGURE 11-Dremel making TEMPLATES
Drilling many identical panels at once:
After a layout has been perfected and many copies of the EWB are to be made, a drilling template is the best approach. Many circuits can be drilled on a single panel at the same time, and several panels can be stacked together at the same time as well. My method is to first drill a stack of mater templates from an original template on the small Dremel drill press ( Model 220-01), using one of those tiny solid carbide PC bits (Harbor Freight 34640-2VGA ). Stack the panels 3 or 4 high, drilling through the master with the same size bit. Prepare as many master clones as needed to complete all the panels in a project run, always save the master for future.
Stack your master clones on top of up to 5 bare panels for final drilling to the proper size, in my case I use a 4" drill press just for this function (Harbor Freight ITEM 44506-1VGA).
FIGURE 12-Drill press for making 3/32" holes
Larger holes for potentiometers, variable capacitors etc. may either be drilled or punched using any of the common methods, many of which we will cover in the metal working chapter. Odd shapes can be sheared or nibbled with a sheet metal nibbling tool. Routing shapes is also possible using a Dremel and 1/8" solid carbide router bit.
Once the holes are drilled, brass eyelets of the proper size are installed in those holes.
Made by Keystone these eyelets come in a variety of diameters and lengths.
When transistors and 1/4W resistors are the main components I like to use the 3/32" diameter. Naturally the bare board thickness must determine the length selected. I use the .060 thick board material so the eyelets of and .093"(Mouser 534-33) or .125"(Mouser # 534-34) length are fine.
INSTALLING THE EYELETS:
This step is simplicity itself, as shown in the picture you need only a small ball-peen hammer and some sort of anvil. Insert the eyelet fully into the drilled hole and peen it over ion the backside using the round part of the hammer. I made my general-purpose bench anvil from a short piece of railroad track and have them in different gauges and lengths. This particular has its faces milled to be flat and parallel, making it a multi-use tool. Also shown is a small fixture for installing an eyelet in a difficult location, it is made form some cold rolled steel stock with a piece of ¼" rod stock as the anvil. In situations where many wires or large wires are to be inserted into an eyelet, the homemade swedging tool is used to expand the eyelet a bit.
FIGURE 14-Eyelet installation tools
I've sort of rambled in this article but wanted to address as many questions as possible on this topic up front. The photographs should make the text clearer and mostly the whole procedure is intuitive anyway.
In the beginning stages of developing this method, I ordered a hundred eyelets. The next order (only a few DAYS later) was for 1000. Now I order the 10,000 at a time and still run out! The larger the quantity, the cheaper they get. Small orders cost about 6 cents per hole, but we can approach 1.5 cents USD per hole with bulk buys. I may be interested in bulk buying the eyelets and the bare board material and reselling them at reduced cost for small users, and the boards can be supplied sheared to size.
© 2007 George Dowell, Viscom Inc.