Copyright 1999 R.G. Keen All rights reserved
Dots and Dashes
Point to Point
Printed Circuit Board
If you're into building your own electronics, having a vast array of prototyping skills and tricks is incredibly useful. The urge to build something doesn't always happen when it's convenient or when you have just the right materials. Here's a collection of useful methods and tricks for building circuit boards.
Some things are common to all the various ways to build circuits. Any way to connect parts that satisfy the common necessities will result in a working circuit. Some of the critical items are:
You have to interconnect the parts correctly
You have to mechanically support the parts. Usually, the part leads themselves are NOT enough to hold the whole mess of parts together all by themselves (as in the Hanging Garden style) and you have to have some way to hold the bodies of the parts firmly. While the leads support the parts on PCB's and other board-style setups, they don't support all the other parts as well - the board does the heavy duty holding, while the leads just hold the one part to the board.
You have to have some way of supporting connections to parts that are not physically close to the circuit - for instance panel mounted jacks and pots. I refer to these as "off-board connections"
You have to be able to mount the circuit inside some kind of enclosure for all but the most temporary, bench top testing. This usually means some kind of supporting board for the circuit with holes in it so you can screw it to supports, but may mean some kind of edge guides as well.
I'll refer to "nodes" - a node is a connection between two or more components. If two resistors are connected together in series, the connection between the two of them is a node. If a transistor base is connected to the junction of the two resistors, it's still just one node. For most circuits, lots of things connect to power and ground. The power supply point is one node with lots of things connected to it. Same for ground.
From the true, original meaning. Get a piece of wooden board, lay out the parts in the arrangement that they actually fit well on the board, then drive a small nail at each "node". Wrap the leads around the nails, trim and solder the leads to the nails. The nails provide mechanical stability for the connections, the board holds the whole assembly together. The earliest "breadboarded" circuits were actually built this way, on an actual kitchen cutting board, and it's where we get the term "bread board" for prototype circuits.
Notice that if you use a thin piece of something like 1/8" luan plywood and brass brads, this can actually be a very useful technique. You could do a very workable simple circuit this way. I'm thinking of making a Fuzz Face clone in this style just to take it's picture.
Also note that while Breadboard can accommodate anything with an extended lead, parts like integrated circuits which are pre-clipped for printed circuit use are very difficult to include. You could, of course, wire up an IC socket with small wires going to one nail/node per IC pin in a partial use of the Dead Bug technique noted later, but there are better ways to breadboard with IC's.
If we'd like to get away without the bulky, wooden board, we can dispense with the board altogether and just lay the parts out on a flat surface and solder them where the cross, maybe twisting the leads together at joints for reliability. The circuit can usually be laid out to closely follow the schematic diagram in many cases if no integrated circuits are involved, and so it's fairly easy to see how to debug. The down side is that without some means of supporting the lattice of parts, the whole circuit is mechanically fragile and almost certain to fail with the slightest bending or twisting. To avoid this, the whole circuit can be laid on a bit of cardboard, plastic, etc. and some casting resin poured over it. When the resin hardens, the circuit is going to still be functional, and now the resin will prevent most bending, twisting and shorts.
The Hanging Garden Style will accommodate IC's to the extent that you are careful about wiring to the IC leads. It helps if you bend every other lead on the IC (or socket!) out at right angles to the orientation of the other pins just to give yourself some room to work.
Which leads us to dead bug building. This is a variation of the Hanging Garden that gives a nod to reliability. The parts are first glued, leads up, into place on some substrate, like a bit of phenolic board or even Plexiglas. The leads are then formed to make the joints, soldered, and trimmed. When the circuit is tested and proven to do the proper task, the whole thing can have reliability poured over it in the form of casting resin just like the Hanging Garden. Note that the resin can be a minimal layer just to bond the parts permanently to the substrate if you have a solid substrate like phenolic, Plexiglas, countertop laminate, glass-epoxy board, or something similar. It can also be poured in a thick layer if the substrate is something that will not supply much support, like cardboard. You can cover the whole mess up entirely if you like solid-block circuits.
Dead Bug can accommodate IC's fairly easily.
The Dead Bug technique is also useful for partial circuits, notably when you have an IC that has a different pinout than a printed circuit board was designed for. You glue the IC's top surface to the PCB, legs up (hence the name, "dead bug") and then run small wires to the holes to rescramble the pinout to what the board expects.
One step more modern than the true wood-and-nails breadboard is "Dot and Dashes". This is a trick used by some amateur radio experimenters. For Dots, you cut or punch a number of small bits of printed circuit stock, perhaps 0.2" (5mm) across, out of a bard board of double sided copperclad. There are cheap (US$20.00) hole punch sets at some tools suppliers that makes this easy. If you have access to a shear, this can also shear up rectangular bits of copperclad board (Dashes!) easily. With your dots, you glue or solder the dots down to another board (glue for non-copper clad substrate, solder for copperclad). The dots form solderable, insulated islands of copper over the substrate. Using a copperclad substrate allows the whole copper substrate to be grounded, which is very good for RF building, and usually OK for audio.
Dots and Dashes are too large to easily accept IC leads, as the size of a usable DOT is just too big for the 0.1"/2.5mm spacing of most IC leads. A hybrid version is possible, setting the IC's down in Dead Bug Style and using Dots for everything else.
A quicker and dirtier version of Dots just does a Hanging Garden, but every lead that goes to ground is taken straight down to the ground plane and soldered. The ground leads hold the whole Hanging Garden up off the copper clad and give it a little rigidity. This is probably OK for quick prototyping, but not good for permanent use unless you pour some casting resin over it for permanent mechanical support.
This is one trick that another web site promoted. You do a layout of the parts, as straightforward from the schematic or as extensively and compactly folded as you like (and can follow!), then print the layout on paper. The layout is glued to a piece of thin cardboard, and the component leads simply poked through the cardboard, using a needle or nail if you need help making holes. The leads are then bent together and soldered, very much as in a hanging garden or perfboard styles. Cardboard prototyping can be viewed as a somewhat improved Hanging Garden, or a cheesy, insubstantial perfboard - it's about halfway between them. This is another style where you really have to use some sort of fixative for long term stability, with casting resin or some such. Note that there are some problems here - cardboard absorbs moisture from the air very quickly, and laser printing is slightly conductive, so that circuits with high impedances, like JFET, CMOS or MOSFET devices and IC's, maybe even Darlington transistors, may act strangely on wet days, or when flexed. Casting the whole mess up in resin should seal it permanently, though, so you're only left with the conduction through the layout printing to worry about.
Like Breadboard, Point to Point is a very old technique. In PTP, you use terminal strips to mechanically secure the nodes of the circuit, placing a terminal strip wherever you need one and using insulated wires to go longer distances than component leads. This can produce VERY high quality results if done with care. However, it's big, bulky, and mechanically difficult (drilling and riveting those terminal strips in). It's often thought of as the ultimate vacuum tube technique, though. Maybe not so good for effects. Completely intolerant of IC's except for the trick of using a partial Dead Bug section to paste in an IC.
Another holdover from vacuum tube days is the combined Eyelet/Turret board. In this form of building, an insulating substrate, like glass-epoxy, phenolic-paper, or rubberized fiber board is fitted with either brass eyelets or pressed-in machined turrets as places to form soldered nodes. This is the standard method that Fender used for all of its vacuum tube amplifiers until modern economics forced them into printed circuit boards. The military was the user of most of the turret board assemblies, which tended to be made on thick (1/8" or 3.5mm) glass epoxy boards. The turrets stick up above the surface of the board and make it very easy and fast to wind the component leads once around a turret and snip the lead to length. Additional interconnection between turrets and external controls, etc., is done with wires. Eyelet board is an even faster way to build, just stick the component leads through the eyelet hole and snip to length. However, eyelet board is not as robust mechanically, each solder joint not having that stabilizing wind around the terminal to steady it. Neither Eyelet nor Turret Board is particularly good for effects, but they're great if you're building tube amps - particularly if you can make or buy your own turret boards.
Again, completely intolerant of IC's except for Dead-Bugging a partial section.
Plugboard is a much more modern update of point to point or breadboard. These are the common "experimenter's strips" you see made of white plastic. They have a central split just wide enough to accept the typical legs of a Dual Inline Package (DIP) IC, and rows of five holes running outwards from that. Each group of five holes is connected together by a strip of metal contacts inside the plastic, and the holes and contacts are set up so you can just push the common component leads into the hole and have connections between the leads - that is, every row of five holes is a potential node.
Wiring up circuits on plugboard is fast, effective, and an outstanding way to try new circuits. It's also incredibly UN-reliable, as the twisting of leads in the holes, sprung contacts and general haywired-ness of circuits on plugboard mean that they'll only work for short periods of time, and there is no good way to solidify them - unless you want to pour resin all over your plugboard! This is usually the best way to test circuits or sections of circuits before committing to a final soldered-down prototype, though. Very good at the limited thing it does well.
Plugboard is a natural match for Dual Inline Packaged (DIP) IC's.
This and strip board is where nearly everyone starts. Perfboard is usually phenolic-paper or glass-epoxy sheet, maybe 1/16" (about 1.5 to 2mm) thick, and drilled with a matrix of holes on a rectangular grid, often 0.1" (2.54mm) centers. With perfboard, you just stick the component leads through the holes and then bend, twist, and trim leads to make nodes. When all the nodes are soldered and trimmed, the board is done. Perfboard is forgiving, mechanically stable, and can be very reliable. It approaches the permanence of printed circuit board, and is a great prototyping technique. In fact, about the only drawback of perfboard compared to printed circuit board is that you'll be tempted to make another one - and then it hits you: each perfboard is a separate work of art, with custom bent leads and wiring. I find that I can only stand to make about two of any one thing on perfboard. However, if you're only ever going to make one, perfboard is a good choice.
Some perfboards have a copper pad around each hole. If you can get this stuff, it is a full notch superior to ordinary perfboard, as you can hold parts in place by just soldering the lead to the pad around the hole it pokes through.
Perfboard with rows/columns on 0.1"/2.5mm spacing is a natural match for IC's.
Perfboard is kind of a PCB minus, and recently Aron Nelson suggested that all it really needs is a way to "paint" traces on the bottom, especially if you have the kind of perfboard with pad-per-hole copper. There are a few ways to do this.
You can think of stripboard as perfboard on steroids. One side of the perfboard is covered in printed circuit traces all running parallel in one dimension. All the holes along one strip would be connected together if you just poked wires through the board and soldered. The whole trick to stripboard is preliminary layout. You place components and dual in line IC's on the blank, non-strip side perpendicular to the parallel runs of strip on the bottom/soldering side. You use the strips as side-to-side printed circuit wiring, and cut the strips apart where you don't need holes connected together. This way, the pre-printed strips can be used for a great deal of the interconnections, and the components themselves make many of the between-strips connections. Jumper wires do the rest. Stripboard is much easier to replicate than perfboard, as there's much less "arts and crafts" manual bending and forming needed to make a second copy. About the only disadvantages of stripboards for protoyping is that they're less modifiable than perfboard, as you had to cut those strips, which customizes the layout of the board, and they're inevitably going to be bigger in physical size than either well-laid-out perfboard or PCB for the same circuit, as really using the strips well necessarily means placing parts in a less compact layout than either perfboard or PCB.
Depending on what you're doing, PCB's are either the King or his evil twin. PCB's are not good for prototyping at all, as the circuit is already cast in concrete in the more-or-less intricate interconnections printed on the board. In fact, it's a bit foolish to waste the time making a printed circuit board for a circuit that you have not already tested and know that additional components are not needed.
However, if you're making your second (or third, or fifty-seventh) copy of a circuit, PCB's are a godsend. PCB's were invented explicitly for making hundreds - or millions! - of copies of circuits that come out right first time, every time. PCB's have the highest possible component density of all the circuit building techniques, and the highest chance of making successful copies, as all the guesswork about what to connect to what is gone.
What's best? Like they say, it all depends. I like to think of all of these as ways to attack circuit problems, and I'll use any one, or any combination of them as needed. Here's a table to summarize the lot of them, on scales of 1-10 for well-executed, well thought out circuits:
|Style||Planning needed||Care needed in Assembly||Modifi-
|Smallness||Lightness||Reliability if done well||Easy IC's?*||Ease to copy|
|Dots and Dashes||2||3||5-10||3||6-8||6||N||2|
|Point to Point||3||5||5||1-5||4||7-10||N||4|