Before and After

This is the final product (on the right-hand side), compared to the prototype it is replacing (on the left-hand side). In electrical terms the prototype and the new board are the same, but the new board is obviously more compact and neater.

Completed

Here's the completed board, with all the components in place.

Capacitors, diodes, transistors.

In a similar manner to the resistors, the other components are added. In this pictures the diodes, capacitors, and transistors has been added. One has to be careful with these, because the diodes and some of the capacitors are polarized, and need to be inserted in the correct orientation. Similarly, the transistors need to be properly oriented, because their three leads are not all equivalent.

Inspection

Once the resistors have been placed and checked it is time to trim. A sharp pair of cutters are used to snip off the leads close to the board. I then used a magnifying glass to inspect each solder joint and make sure that there is a good connection to the conducting tracks.

Resistors

The first component that I put on the board were the resistors. One has to be careful with them, because they are all small and of the same size and shape. They are distinguished only by a colour code painted in rings on the body of the resistor. On the right-hand side I show a resistor that has not been installed yet. Its legs are bent to fit the holes on the printed circuit, inserted, and the soldered on the bottom side.

The printed sheet of paper in the background is the component list of the circuit, extracted by the software from the schematic. I used it to check that the right resistor went to the right place, and that none were forgotten.



This pictures shows the 'solder side' of the board after all the resistors have been placed. See the leads sticking out at the back.

Factory Fresh.

I sent a PostScript file to James at C-Boards, and about an hour later he let me know that my board was ready.


This is what I got from him: my circuit layout in real life. It is a glassfibre reinforced phenolic board, with conducting tracks of copper, plated over with tin, ready for soldering. There are holes of the right size drilled at the right places.

Artwork

When I was pretty sure that everything was OK, it was time to manufacture.
I extracted the 'artwork', i.e. the design that I wanted from the manufacturer. This picture shows more-or-less what I sent to the etching shop.

Checking the layout

In design the question in the background is always "will it work?". One should always try to answer this question as soon as possible.
Here I've made a printout of the board layout, and have laid out the components in their positions to see if there is actual space on the layout, and if all the components on the schematic are the correspond to the ones purchased.
At this point there are no obvious problems in the layout.

The Circuit Board Layout

In real life components have certain sizes, and they need to fit into a certain space. The circuit board layout shows how the components will be arranged on the printed circuit board. The outlines shows the placement of the components, while the labels next to the outlines refer to the symbols on the circuit diagram. The blue lines show how the components will be connected electrically.

The beauty of using software for this job of converting the schematic to a board layout is that when one makes changes in the schematic the board layout is automatically updated to reflecte the changes.

The Schematic Circuit Diagram

This is where it all starts. The electronic engineer designs a circuit, and draws up the schematic circuit diagram. This is the conceptual idea of how the current should flow and how it must be controlled to produce the desired result. It is the language of the electronic engineer, and like any language it can be written well or poorly, and there are different dialects. This is my attempt at expressing the circuit that was designed by my predecessor.

The Printed Circuit Board

Electronic devices are ubiquitious. We casually wear them and carry them in our pockets and let them handle our money and help drive our cars and never give them a thought until they stop working.

Perhaps surprisingly, the basis of electronics are a few types of basic components, assembled in circuits that contain from a few up to thousands of components.

The explosion in electronic devices over the last fifty years is due to a number of technologies, one of which is the printed circuit board.

This in turn depends on a technology familiar to the ancient Romans, called soldering.

In my speech at Wednesday's meeting I will explain and demonstrate soldering and the process of producing printed circuit boards.