Prototyping Electronic Circuits

Discussion in 'General Electronics Chat' started by Wendy, Apr 24, 2011.

  1. Wendy

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    Mar 24, 2008
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    This is a work in progress, an article about the various types of prototyping and breadboarding electronic circuits.

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    In any project eventually the next step is building the circuit. This applies to one time knock offs by hobbiest to a professional who is building the 1st round of a circuit before turning it over to manufacturing. For home users the projects may wind up as hardware that will serve some practical application to an experiment that will be disassembled to reuse the parts.

    Many of the terms used for these circuits are ambiguous, so I will define them as I go. Many people will disagree with the specific definitions.


    Prototypes

    A prototype is usually the first attempt at building a circuit that has not been built before. It doesn't have to be the first, occasionally more than one version is built to improve on the previous version, or a hobbiest is building a circuit from a schematic for their own use.

    Generally, when building a prototype of any sort, neatness counts. This can not be emphasized enough. A rats nest of wiring may work, but the neater a project looks the more likely it is to work the first time it is power up. Part of this is the thought you put into the layout means you are less likely to make mistakes, and part of it is the wires are likely to be more point to point. Keeping wires short as possible is important, especially with higher frequencies.


    Breadboards

    This is probably the most ambiguous term out there. It's roots are based in the 1920's and 1930's, where enthusiasts would buy a breadboard (literally, meant to be used for cutting bread) or grab one from the kitchen and start mounting terminal strips and tubes and wiring their circuits. When I was a teenager I used old lumber and these kind of terminal strips to breadboard various types of transistor circuits, mostly oscillators.

    This part is available from Radio Shack (PN 274-688), but many other sizes can be bought from other vendors, such as this assortment from Dan's Small Parts and Kits.

    [​IMG]

    Breadboarding can also mean using a protoboard, similar to this...

    [​IMG]

    My personal definition of a breadboard is any type of construction technique other than printed circuit boards. It is a generic term. Protoboards will be discussed later in this article.


    Perf boards

    This type of prototyping or circuit building dates to the 1950's, when component sizes started coming down, and transistors were just getting started. They were a fiber glass or phenol board with holes drilled at regular intervals. There were also tiny tubes (AKA valves) that were meant to solder into a board similar to transistors. Early perfboards had no copper pads, but latter versions with pads were developed . The more common types use the 0.1" spacing. It is interesting to note that metric is slowly taking over component dimensions, but the American system is still very common because DIP chip packages were well established in the 1960's. Many people start with a blank board and build, but I like to lay it out on paper first. Here is an example of how this would work...

    Project: High Power LED Flasher

    [​IMG]

    It has the advantage of handling medium frequency RF applications very well, especially if the leads are kept short and the circuit layout kept neat. The schematic will offer major hints in how the perfboard should be laid out.

    The number of perf board derived schemes have expanded. A few are shown below. Generally they are referred to as strip boards, because the patterns have strips to allow easier construction.

    [​IMG]

    The ultimate in stripboard is Veroboard, a trademarked in the UK by Vero Technologies Ltd. It is a bit different from other examples in that the hobbiest will need to slice and remove small pieces of copper strip with an exacto knife to isolate parts of the circuit. It can be very neat in appearance, and works well for high frequency applications. Shown below is a drawing of a blank board along with an FM transmitter around 100MHz made with this material.

    [​IMG]
    ............................................................................................................................................Courtesy of AudioGuru

    This material can be hard to get in the southern United States, but is worth mentioning as it is fairly common in the Northern United States, Canada, and the UK.
     
    Last edited: May 8, 2011
  2. Wendy

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    Mar 24, 2008
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    Protoboards

    This is probably one of the most popular standards anywhere. When people say breadboard, this is the first thing many think about, and you will get the occasional argument that the term breadboard only refers to this product. It tends to be one of the first purchases a beginner in electronics makes, due to its obvious utility and ease of use. Many schools and colleges require purchasing one for their course subjects.

    The term protoboard is fairly ambigous, and can refer to several construction techniques. For the sake of arguement this style of protyping will be referred to as a protoboard.

    [​IMG]

    It does not work well for high frequency or RF projects, nor does it handle high current applications well (2A or more). What it does do is allow complete reusability of all the components, including the wire. It was invented in the mid 1970's, and is currently made by several manufacturers. The older models tend to be much higher quality, while the new versions (which are usually made in China) tend to have reliability problems over the long term, although the layout is much better overall. They come in several configurations, such as short and long boards, and are designed to interlock to make even larger circuits than a single protoboard can hold. There are even printed circuit boards that use a layout close to a protoboard to allow the transfer of a working circuit using a protoboard to something more permanent.

    While not good for high speeds (1Mhz or more) protoboards are excellent for audio and ultrasonic, and may work for low frequency RF projects. The problem is the parallel rows of 5 pins act like capacitors, adding an unwanted component to experimental circuits. Protoboards also work quite well for digital projects.

    Most beginners tend to build these circuit haphazardly. They still work, but it can cause a lot of unwanted problems, such as allowing signals to cross talk in the wires. A better approach is to have the wires go point to point, and site flat on the board. I tend to draw this when I illustrate my articles. I suspect many people think this is just the drawing, but it isn't. With complex projects this may not be an option. Basically keep the wires short and neat as possible for an intricate project.
     
    Last edited: May 13, 2011
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