This page last updated on Thu, 19 Jan 2017 00:44:17 +0000

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A FREQUENCY COUNTER PROJECT - Part-4
(Designing and Producing the Printed Circuit Board)
Dieter (Diz) Gentzow -- W8DIZ                                             w8diz@tampabay.rr.com
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PREFACE:
Part-4 is the final chapter of the Frequency Counter Project.
In Part-1, we installed Linux Mint as the PC Operation system environment for the project.
In Part-2, we created a schematic using free tools from http://expresspcb.com
In Part-3, we learned about Assembly Code using AVRA and uploading firmware using AVRDUDE.
This final chapter, Part-4, we will designing a PCB using free tools from http://expresspcb.com
All addendums and/or corrections to this project are available at http://w8diz.com/qq-fc-project/

DOWNLOAD TOOLS AND DOCUMENTS:
It is assumed that you have followed this project from Part-1 thru Part-3. If not, you will
need to go to http://w8diz.com/qq-fc-project/part-2/ and install WINE first,
followed by EXPRESSPCB.  If you are on a Windows machine, go to
http://expresspcb.com and download and install their free CAD software package. In both cases,
install EXPRESSPCB using all the default settings.

LEARNING TO USE EXPRESSPCB SCHEMATIC CAPTURE PROGRAM:
ExpressPCB has been my Printed Circuit Board Vendor of choice for ten years.
They are not the cheapest PCB vendor by far, but they are reliable and provide an end product that is second to none,
and their free proprietary software is very user friendly and easy to learn.
ExpressPCB offers a "MiniBoard" service, which uses a predefined board size of 2.5" x 3.8".
Cost to have three such PCB prototypes mailed 2nd day air to your door is about $60.
Production runs of 100 "MiniBoard" PCBs produce boards at a cost of about $5 each.
Double-click the ExpressSCH.desktop icon on your desktop.
Ref http://w8diz.com/qq-fc-project/expressPCB.gif


Click on "Help" in the Menu Bar and review their User's Manual and the Quick Start guide.
Play with all the buttons and try the examples and suggestions in the guides.  When you think
you can move around the program, close the program and restart it.

Let's check out the default PCB layout options: Click on "View" followed by "Options".
Ref http://w8diz.com/qq-fc-project/options_pcb.gif

Since we are dealing with 1/10 inch PIN spacing on the sockets, the default GRID SPACING of ".100" works well.

We will now create several components for placing on the screen, starting with the IC sockets
for the ATtiny2313 and the 16 pin DIPS.  Click on the "Place a Pad" button. 
Ref http://w8diz.com/qq-fc-project/select_hole.gif


Then select the pad/hole size. 
Ref http://w8diz.com/qq-fc-project/select_size.gif


A pad/hole size of 0.065/0.035 will accomododate ZIF socket pins as they are larger than normal socket pins.
For normal socket pins, select a pad/hole size of 0.056/0.029
Also note that you can select either a round or square pad.  Select the square pad for PIN-1.
Place one SQUARE pad on the layout sheet followed by 19 ROUND pads.
Spacing is 0.1 inches for each row of inline pads.
Position the pads in two rows, spaced 0.3 inches apart.
Click the "Arrow" button and Select the entire part per the picture below.
This is done by positioning the cursor past the upper-left corner of the part,
holding down the right mouse button, drag the mouse to the lower-right corner
and then release the mouse button. This selects the entire part. 
Ref http://w8diz.com/qq-fc-project/select_comp.gif

Now click on "Edit" and then "Group".
Ref http://w8diz.com/qq-fc-project/group_pcb.gif

We have just created a 20 pin dip component part that we can move anywhere on the layout sheet.
If the created part is still GRAY in color, click the background of the layout sheet.
Click on the part and mouse-drag it anywhere on the layout sheet.
Now let's create a standard 16 pin dip part, including some artwork in addition to the holes/pads.
Replcate the procedure to create the 20 pin part but create a 16 pin dip component.
Ref http://w8diz.com/qq-fc-project/dip16.gif

Click on the "Place a Trace" button and select the YELLOW line color on the top Menu Bar.
Replicate the artwork per the above picture. Group the elements of the part just as you did for the 20 pin DIP.
This finishes the creation of the IC/Socket components.

When creating a new part, instead of starting from scratch, it is often easier to copy an existing part, Edit/Ungroup it and reorganize the items into a new part.
Let's create an Electrolytic Capacitor part that is 0.2 inches diameter and 0.1 inch lead spacing.
Click on the "Place a circle or arc" button, then, on the upper menu bar, select the yellow "Silkscreen" layer,
the "Circle" button followed by a radius of 0.1 inches and a line width of 0.010 inches.
Now position the cross-hair cursor to an empty spot on the layout screen, click the left mouse button and drop a yellow 0.2 inch diameter circle.
Click on "Place a Pad..." and place one square and one round hole/pad size 0.056/0.029, spaced 0.1 inches apart, in the center of the yellow circle.
Next, click on "Place a Trace" and draw a yellow plus sign near the square pad. The part should look like the below picture.
Ref http://w8diz.com/qq-fc-project/ec1.gif

Click the "Arow" and Select the entire part.Now click on "Edit" and then "Group".
If the created part is still GRAY in color, click the background of the layout sheet.
We now have an object for a small Electrolytic Cap.  To make a larger capacitor,
click on the new part to "Select" it. Now let's do a copy and paste by doing a CONTROL-C
followed by a CONTROL-V on the keyboard. This action will create a duplicate part in the center of the layout sheet.
Move the newly copied part to an open area on the workarea. While the part is still colored gray (Selected),
click on "Edit" followed by "Ungroup". Now click the background to un-select the new part.
Double-Click on the Circle on the new part and change the Radius from 0.1 to 0.15 inches.
Next, click on the pads and move them 0.2 inchaes apart, keeping them centered in the circle.
Now move the yellow PLUS SIGN lines toward the square pad. Click the ARROW and SELECT the entire part.
Now click on "Edit" and then "Group". We now have a second larger part than the original.

For mounting PCB holes, select a square or round pad/hole size of 0.160/0.125
This hole size is perfect for mounting the PCB using standoffs and 4-40 size threaded screws.

To make connections between pins, select the "Place a Trace" Icon, then select the trace color and width.
The default color for the top layer is Red; Green for the botton layer.
Yellow is the default color for the SilkScreen layer on the top of the PCB.

Ground Planes:
For RF work, it is usually a good idea to have a good Ground Plane on the PCB layout.
ExpressPCB allows you to create an automatic ground plane by clicking the "Place a Filled Plane" button
or create a ground plane manually by using the "Place a Rectangle" button.
I do not like the automatic version, but your mileage may vary; give it a try.
Being a control freak, I prefer the "Place a Rectangle" method.
Another preference I have is to attempt to keep all interconnection traces on top of the PCB (Red Layer)
and place the ground plane on the bottom of the PCB (Green Layer).

Common Errors:
The most common errors made in PCB layout designs are hole sizes that are too small to fit component leads/pins
and creating incorrectly sized components that will not fit next to other components on the PCB.
Another common error is to use 0.1 inch spacing for component leads that have 0.2 inch spacing and vice versa.
After you make these mistakes several times, you will notice a burning in your pocketbook.

Download the completed PCB dsign:
You can download the completed PCB layout from http://w8diz.com/qq-fc-project/ATtiny-FC.pcb
Place this file into your ExpressPCB directory.  Note that there are two halves to the PCB as
only one half of the "MiniBoard" service PCB size is required for the Freq Counter.
The other half of the PCB is my 5 watt A1 amplifier, Ref http://kitsandparts.com/qrp_amp.php

How to order the PCB if you use Linux:
Download the latest pricing file from http://www.expresspcb.com/pricing/
and move the "Pricing.dat" file to your "ExpressPCB" directory.
This directory is located at /home/your_home_directory_name/.wine/dive_c/Program Files/ExpressPCB/
With your PCB file loaded, click on "Layout" followed by "Generate Plot File For Manual Order"
Ref http://w8diz.com/qq-fc-project/plot.gif

Follow the instructions by filling out your personal information, then select "Miniboard Service"
and then "Miniboard", 3 boards for $51.  The quantity defaults to 3 boards.
Enter your credit card information and finally click on the "Plot" button.
This will create a Plot File with a name like "NNAT5381M.PLT". 
Note this name and directory path on a piece of paper or print the screen for future reference.
Now we need to Upload this Plot file by going to http://www.expresspcb.com/submit/.
Once the file is uploaded, ExpressPCB.com will send you an acknowledgement via email.

How to order the PCB is you use Windows:
Download the latest pricing file by clicking on "Layout" followed by "Update Pricing File".
Ref http://w8diz.com/qq-fc-project/pricing.gif

Then click on "Order Boards Via the Internet...". More info is available at http://www.expresspcb.com/ExpressPCBHtm/Order.htm

Finally, I found a doc file tutorial available from the web that may be useful.
Get it at "http://www.usna.edu/EE/ee241/EXPRESS PCB TUTORIAL.doc"
and on my web-site at http://w8diz.com/qq-fc-project/usna.edu.express_pcb_tutorial.doc

ABOUT THE AUTHOR:
Dieter (Diz) Gentzow, W8DIZ, aka WB8QYY before April 2000, has been a licensed ham since 1973.  
Past employment include Honeywell as an Industrial Sales & Systems Engineer,
AC Nielson, Electrical Engineer designing black boxes that monitor TV viewing habits and 
a handful of other hardware and/or software jobs.  
Currently semi-retired, living in sunny Palm Harbor, Florida.  
You can contact Diz, W8DIZ via eMail at w8diz@tampabay.rr.com

NOTES:
Any addendums and/or corrections to this project will be available at http://w8diz.com/qq-fc-project/