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Construction Techniques
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Construction Techniques

Presented here are many ways the experimenter may assemble electronic circuits. Some are inexpensive and easy to make from readily available materials. Others are more expensive, not very reliable or perhaps even obsolete. All of these techniques are showcased here because it is useful to be aware of all the possibilities and options. When in a pinch or a hurry, you can resort to the technique that best suits the situation.

 

Point-to-point wiring

Point to point on acrylic

Components are wired directly and suspended in air or mounted on an insulating material such acrylic, Plexiglas or Lucite. Components may also be soldered to metal terminals or posts mounted on teflon standoffs. This technique is used when dealing with very high voltages in excess of 1KV or higher or when you want the lowest possible leakage currents.

Applications
Advantages
Disadvantages
High voltage, power components, ultra low leakage currents Simple, no special hardware required Bulky, not suitable for complex circuits

 

Terminal Posts

Point to point on posts DEC prototype card

Metal posts are commercially available which can be mounted in many types of insulating materials. Component leads and wires are wrapped around the posts and then soldered to create a sturdy joint.

Applications
Advantages
Disadvantages
High voltage, power components, ultra low leakage currents Simple, no special hardware required Bulky, not suitable for complex circuits

 

Tag/Lug/Terminal Strip

Solder Lugs

When assembling bulky components such as large power resistors, rectifiers, capacitors, transformers (you guessed it - as in building a power supply) it may be easier to just bolt or screw terminal tags or lugs on to the chassis, whether metal or wood.

Applications
Advantages
Disadvantages
Power supplies Simple, low cost construction Bulky, not suitable for small components

 

Breadboard and screws

Breadboard and screws

This is perhaps the origin of the first "breadboard". It is the simplest, cheapest, easy to make and modify, durable, robust and perfect for school projects and classroom demonstrations. Now, don't go and use mom's breadboard if you want to eat dinner tonight but get yourself a scrap piece of softwood like white pine, about 1cm or 1/2" thick and any suitable size. Of course, if you choose to use plywood instead, this is called SOP technology, or Silicon-On-Plywood : )

Sand the edges to remove any splinters. Find some #6 x 1/2" pan head metal screws and you're all set to go. You can mount the screws any place you like or you can pre-drill the board with 3/32" holes on a 1" grid pattern. Flat washers on every screw will help to secure your wires.

Applications
Advantages
Disadvantages
Prototype, school projects, classroom demonstrations Simple, no special hardware required Bulky, not suitable for complex circuits

 

Battery Terminals

Project board

You can be creative by reusing old battery thumb caps. These are perfect for creating classroom demonstrations.

Applications
Advantages
Disadvantages
Prototype, school projects, classroom demonstrations Simple, low cost, readily available material Bulky, not suitable for complex circuits

 

DEC Jumper Cables

DEC cables DEC modules DEC wiring

Here is a great way to get young folks involved in building electronic circuits. I happen to have a large collection of DEC (Digital Equipment Corporation) jumper cables with mini-banana plugs on the ends from olden days of using DEC Flip-Chips®. I have put these to good use by creating various modules with lights, switches, meters, motors, battery holders and even those annoying greeting card noise makers. The nice thing about these plugs is that they are stackable, allowing you to plug one on top of another. Sockets are made by winding brass wire around a suitably sized nail.

Applications
Advantages
Disadvantages
Prototype, school projects, classroom demonstrations Simple, versatile, easy to rewire Bulky, not suitable for complex circuits

 

Spring Clips

Spring clips demo Spring clips

You may still be able to find a supply of these spring clips which plug into perforated hardboard, Masonite or pegboard. The springs serve the same purpose as terminal posts except you do not solder the joints, allowing for easy modification. Component leads and wires are held in place by the metal springs.

Applications
Advantages
Disadvantages
Prototype, school projects, classroom demonstrations Simple, versatile, easy to reconfigure Bulky, not suitable for integrated circuits

 

Perf Board

Perf board - top Perf board - bottom

Perforated phenolic or fibreglas boards can be used for point-to-point wiring of leaded components. It is a good idea to use sockets for ICs to allow for easy replacement of ICs. Wire wrap sockets will give you a longer pin to work with.

Applications
Advantages
Disadvantages
General purpose discrete components and thru-hole ICs Simple, no special hardware required Time consuming

 

Foam Board

Foam board example

Here is a clever, creative and attractive way to construct hobby projects. Standard foam board 5mm thick consists of foam sandwiched between two layers of cardboard. Punch holes for leaded components and wire wrap sockets. Wire the same way as for perf board construction.

Applications
Advantages
Disadvantages
General purpose discrete components and wire wrap sockets Simple, low cost, attractive  

 

Wire Wrap

Wire wrap prototype board Wire wrap bottom and tool

With the advent of digital integrated circuits in DIP packages, there was the need to assemble fairly complex designs with lots of connections. Wire wrap techniques came to the rescue and entire mini-computers (e.g. DEC PDP-8, PDP-9, PDP-15) were assembled using wire wrap. This and Scotchflex were the quickest way of getting your prototype up and running. This technique is not particulary useful for analog circuitry since component carriers have to be used for mounting discrete components.

Applications
Advantages
Disadvantages
General purpose, digital circuits Fast to assemble and easy to modify Wire wrap sockets are expensive. Not good for discrete components.

 

Scotchflex®

Scotchflex example Scotchflex example

The Scotchflex® breadboard system made by 3M™ is a great time-saving method for prototyping large microprocessor systems that contain a large number of peripheral components and memory chips. This system allows you to bus address, data and control lines from chip to chip with a single wire without having to strip, wrap or solder the wire. At the time of appearance on the market place, this was a great idea which worked well for circuits using DIP components. Microcontrollers today are fully integrated with an assortment of memory and peripherals and hence have made this breadboarding system redundant.

As with wire-wrap sockets, you have to use component carriers to mount discrete components.

Applications
Advantages
Disadvantages
Computer memory and bus systems Fast prototyping of DIP components Expensive, obsolete

 

Component Carriers

Component carrier

Component carriers are DIP (dual-inline package) plugs on to which you can solder leaded components such as resistors, capacitors, diodes and transistors. These can then be plugged into standard DIP sockets. These are handy, not only for prototyping, but also if you want to be able to reconfigure your circuit easily, for example, change the gain or roll-off frequency of an active filter.

Applications
Advantages
Disadvantages
Mounting leaded components into DIP sockets Easy way to reconfigure a circuit  

 

Polyurethane Enamel Coated Wire

UEW example UEW dispenser

Another method of speeding up the wiring of bussed systems is to use polyurethane enamel coated copper wire or UEW. The wire can be dispensed from a simple hand tool which can be homemade as demonstrated by other creative electronics enthusiasts. The heat from the soldering iron melts the polyurethane plastic insulation on the wire and bonds the wire to the solder joint. You keep soldering from point to point and then cut off the wire at the end of the run.

Applications
Advantages
Disadvantages
All applications Fast wiring of digital buses  

 

Solderless "Superboard", "Superstrip", "Wishboard"

Superstrip Superstrip breadboard

The solderless breadboard system is by far the most versatile system available for prototyping both leaded and DIP components. Surface mount devices (SMD) can also be included if you use SMD to DIP adapters or carriers. Prototyping is fast, reliable and easy to modify. Every experimenter should have at least one of these breadboards. For simple portable prototypes you can use a single board and a 9V battery, 3V coin battery or AA or AAA battery packs. For the serious experimenter, build yourself a larger board with three or four boards on top and include a built-in power supply that provides 5V, +12V and -12V, (or +15V and -15V). This will allow you to prototype both analog and digital systems.

Applications
Advantages
Disadvantages
Experimenting, analog and digital circuits Most versatile, easy to modify, leaded and DIP components for prototyping only

 

ISA Prototyping Board

ISA prototype

Well, here is an imaginative solution - a superboard stuck onto an ISA prototyping card. This gives you all the versatility of the superboard while plugged permanently into an PC. Unfortunately, this is now obsolete since they don't make PCs with ISA slots anymore.

Applications
Advantages
Disadvantages
PC mounted prototyping Versatile, enclosed in PC Obsolete

 

Stripboard, Veroboard, Vectorboard

Veroboard Veroboard - bottom Veroboard

After prototyping on a superstrip, you can make your circuit reliable and permanent using copper clad prototyping stripboards made by Vero and Vector. These boards are available in different sizes and connection patterns. For versatility, you can't beat the parallel copper tracks of stripboard. You cut away the copper strips by hand as desired using either a sharp X-acto knife, drill bit, or special hand tool. Interconnections are made using the copper strips by carefully choosing the placement and layout of your components. Additional jumper wires are best installed on the component side, unlike perf board construction. SMT resistors and capacitors can be soldered on the copper side. Stripboard is the simplest solution for both digital ICs and analog discrete components.

Applications
Advantages
Disadvantages
All applications, analog and digital Good for leaded and DIP components Can't think of any

 

Double sided copper laminate

SMT example

For the ultimate in modern design, compactness, low noise and when you must use surface mount technology (SMT), it is in fact quite easy to prototype using SMT components. The end result is a circuit that has all of the advantages of SMT and is clean of noise.

First, we take a suitably sized piece of double sided copper laminate. Since we are talking about SMT, think small. You can put a lot of stuff on a board 2" x 2" or even 1 square inch! The goal is to reserve the bottom side of the board for a ground plane. All components are placed on the top side. The copper circuit is created, not by cutting copper traces, but by cutting away copper strips to create spaces about 0.020" to 0.050" wide or what I call "anti-traces". This is quite easy to do using a sharp X-acto™ knife. You score on the outline of the anti-trace you want to strip off, usually a long rectangular channel, lift up the edge of one end and peel away the copper strip. It peels off quite easily, easier than rolling away a strip of sod off your lawn.

If your design does not require low signal noise and you want to make the board even more compact you may choose to place components on both sides of the board. Since cutting the copper layers by hand is time consuming, this is not recommended for complex digital circuitry. It is possible to remove the copper using a fine rotary tool. In fact, numerical control (NC) machines are available which will mill out the anti-traces using information from a regular PCB layout program.

For resistors and capacitors, I like to stay with 0805-sized components since they are easier to handle and I have a better chance of finding them when you drop one on the floor. For integrated circuits, it is easier to work with components in SOIC (Small Outline Integrated Circuit) packages, with 0.050" pitch. Stay away from anything with MLP (Metric Lead-frame Package) since there are no leads on these.

Cutting the anti-traces, laying out a neat design and soldering the components to create your masterpiece can be a very satisfying experience.

Applications
Advantages
Disadvantages
Low noise SMT analog circuits Compact, low noise SMT design Not suitable for complex digital circuits

 

Printed Circuit Board

PCB sample

When you know that your prototype works and the design is frozen, nothing beats the satisfaction of seeing your creation in a professionally made printed circuit board (PCB). You can start out by making the boards yourself or you can take advantage of the internet and have a commercial shop make it for you. With the advent of the internet and higher demand these are actually not expensive to have made, even for a single board.

Making a PCB yourself, while educational, is also time-consuming and messy. Since it is reasonable to have it made commercially, let us examine that route. Since it is easy to make mistakes in your electronic design and board layout, it is not a bad idea to make a prototype first. Many PCB shops offer a special prototyping service at lower costs. These boards are generally double sided with plated holes but without silk screen overlay (component placement and part identifiers) and solder masks (the green protective layer) in order to keep costs low. Mainly because of the setup charge incurred you can expect to pay around CAD$50 to CAD$75 to get a couple of boards made. Turn-around time is usually short, one to three days at the most. After you have tested the prototype and have corrected all your mistakes you can go ahead and make your first batch of 100 production boards! Suffice to say that the experimenter rarely goes into production and is happy to use the prototype service even for a dozen or more boards.

Applications
Advantages
Disadvantages
All applications Professional looking, production quantities Costly for single board

2007.07.29



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©2007 McMaster University, Department of Physics & Astronomy