This page started on 01/03/01 and last updated 01/03/01

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Quick Prototyping Modules

Ron, Alan and Brynn from "Alan's robot workshop" have listened to me talk about "modules" for two or three years now. The "Web Guy" has put up with my never ending threats to make "modules" for over twnety years! I'll bet these guys are going to be glad to see me finally document my ideas and actually start building my first "modules".


When you come up with a project you want to build you have two choices. Build a prototype to test the concept. Or build a "final" version right away. Depending how you build the final version, some people may consider it to be a prototype anyway. So I classify a prototype as a temporary device to test a concept. By this definition the prototype will be disassembled (or at least not used) once a final version is created.

The reason a prototype may be considered a final version is that the same techniques can be used. One method I use (and always say I will never do it again) is point-to-point wiring on perf board. This requires soldering a wire to each pin you want to connect. This method is very tedious and takes alot of patience. However I usually consider it to be earier than making a "kitchen sink" PC board. The main reason is because I don't have to have it fianlized before I start building. The wired perf board could be used as a final version if it works and you don't want to redo it. Or if you go on and make a PC board then it can be considered just a prototype.

Another method that I prefer to point-to-point wiring on perf board is ProtoBoards. ProtoBoards are white plastic blocks that have built-in socket holes. You can plug ICs and associated parts into the boards. You use 20 gauge solid wire to make connections.

[Picture of a ProtoBoard]
A ProtoBoard with a sample circuit.

ProtoBoards are quicker than soldered point-to-point wiring if you have precut wires. If you have to stop, cut and strip the jumper wires it takes alot of time. But when you reuse the wires for the next project it goes much quicker.

The ProtoBoards have other problems. There is an upper frequency limit due to the construction. The metal socket pins are placed parallel to each other in the plastic holder. This causes an approximate 3pf capacitance from pin to pin. I haven't had any problems with digital circuitry that I could prove came from this capactitance but it could be a real problem if you are building analog circuits. People also complain that they don't get good connections with ProtoBoards. I have noticed that most people that complain seem to have abused their ProtoBoards. If you use too large of wire the sockets get stretched out. And indeed you will get bad connections if you have done that.

The biggest drawback I have found to the ProtoBoards is that I do tear the circuit apart so I can reuse the board for the next project. Although I decided a few projrcts ago that it may be cheaper to just buy another ProtoBoard to do the next project. Mainly because of the time it saves me over doing a soldered point-to-point board. So I may indeed have a couple "final" versions on ProtoBoards...


Instead of building the entire circuit from scratch, suppose you build it from small building blocks.

A good example of building block design is the familiar LEGOs building system. LEGOs allows you to create objects by stacking a variety of small blocks and connectors. Then snap on a motor block, or two. Connect a LEGOs progammable controller and write a simple program to make it go. And this is all done from the parts that they supply in the kits. When you get tired of the current creation, you take it apart and build something totally different out of the same parts. This is exactly what I want to do with electronic parts.

[Picture of a LEGOs creation]
A project built with LEGOs.

Think about how handy it is to have an IC that has several gates in one package. If each gate was separate then you would need far more parts on you project. And you can get highly integrated ICs. A good example of this is the Motorola radio receiver chips. They provide the entire active electronics for the receiver on a single chip. You add external parts such as crystals, capacitors, resistors, etc. Another good example is the microcontroller chip. As a designer you don't have to design the processor from a whole mass of logic gates.

You can create small circuits that perform a specific function. A building block. For instance, you could create a display module. It may have several LED displays and some decoder/driver circuitry. You could create a pulse width modulator module. You could input a number and have it generate an output waveform. You create basic modules that can be "snapped" together, just like LEGOs.

The sample project

I need something to focus on so I can define some modules. I will use my video digitizer project as my model throughout this article. I designed the digitizer from an idea and created a working unit. So I have a good understanding of what it takes to make it run. Now I want to recreate a digitizer with reusable "building blocks".

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