This tutorial is to help a novice design a simple Printed Circuit Board. It provides a step-wise guidance in using the software AUTOTRAX to design a PCB for the circuit shown in fig 1.
2) In the screen shown in fig 2 press any key to start the software.
3) In the box that is displayed enter the path and the filename to load an existing file, or press Esc to begin with a new file
Note: AUTOTRAX stores files with a .PCB extension.
4) In the screen shown in fig3, the
square area with a pattern of dots is the board area on which all components,
tracks, pads are laid.
How to design the PCB ?
begining to design a PCB follow whichever of the two is convienient, either
make rough sketch of the layout on paper or go on straight with the software.
The Inductance in the circuit can be realized on a PCB as a circular arrangement of pads as shown in fig 4 with a diameter of 1 inch. pinds would be soldered through the holes and a wire would be wound around the circular arrangement of pins.
An easy method of placing the pads in a circular fashion is to place a pad of 1'' diameter and then place pads of the required size along the circumference of the 1'' pad and then deleting the it.
Making the layout using AUTOTRAX
The Autotrax software provides us with a main menu called 'AUTOTRAX 1.61' and a number of sub-menus with various options to help us design our PCB.
1)Components placed on the board shown in fig 3 will appear too small to work with, so we need to zoom into the board area.
2) Invoke the main menu by clicking the left mouse button, by pressing the enter key or by pressing Ctrl m .
3) Click on the zoom option in the main menu.
4) In the ZOOM menu that appears click on WINDOW option. This is to define a window and to zoom into it. On choosing this option, the text 'SELECT FIRST ZOOM WINDOW CORNER' will appear on the status bar at the bottom of the screen.
Note: Always keep your layout as lose as possible to the origin of the board. The grid co-ordinates or are shown on the status bar.
5) Select one corner of the required window by left clicking the mouse at that point and then the diagnally opposite corner in a similar manner as shown in fig5, this will zoom into the window defined.
6) To change the change the unit of the grid co-ordinates to METRIC (mm), select the 'CURRENT' option from the main menu.
7) Choose the GRID option in the menu that appears. Menu named GRID SYSTEM appears.
8) Select the METRIC from this menu. the co-ordinates displayed in mils on the status bar now change to mm.
9) Select the MAIN MENU --> PLACE --> PAD OPTION.
10) place the pad by clicking the left mouse button at the desired location.
Note: Always remember to deselect an option afterusing it, by pressing Esc.
11) The pad placed needs to be edited to the desired size.
12) To do this select MAIN MENU --> EDIT --> PAD option.
13) As per the status bar indication select the pad to be edited by clicking on it.
14) On selecting the pad to be edited, menu called EDIT PAD will appear. Select X-SIZE option in this menu. A box called PAD X-SIZE will appear.
15) In this box, enter the size of the pad as 25.4 (1 inch) and press the enter the key.
16) Press Esc.
17) In the menu GLOBAL CHANGE PADS that appears, select 'ONLY THIS PAD' option. A pad of 1'' diameter appears on the screen.
18) Following step 10 and step
11, place pads along the circumference of the 1'' pad as shown in fig
19) To delete the 1'' pad, select MAIN MENU --> DELETE --> PAD option.
20) Click on the 1'' pad. The pad will be deleted, but
the screen will appear as shown in fig 7.
21) To refresh the screen, select MAIN MENU --> ZOOM --> REDRAW option. The screen will now appear as in fig 4.
22) Change the size of the pads to 80 mils. To do this, first change the grid units to mils (Imperial) by following step 6, step 7 & step 8 but selecting IMPERIAL instead of METRIC in step 8.
23) Now change the size of the pad to 80 mils by following steps 11 through 16, but entering 80 instead of 25.4 in the box named PAD X-SIZE in step 15.
24) Now change the hole sie of the pads to 30 mils by selecting the MAIN MENU --> EDIT --> PAD --> HOLE SIZE option and enter the size as 60 in the box named PAD HOLE SIZE.
25) This completes the layout for the inductance. now the other components need to be placed. These components can be placed from the Autotrax library. To place components select MAIN MENU --> PLACE --> COMPONENT option. In the box NAME IN LIBRARY, that appears, enter the name of the component RAD0.2 and press the enter key.
26) In the next two boxes that appear, press the enter
key with out entering anything. The screen will now appear as shown in
27) Press space bar to rotate the component to a vertical orientation.
28) Place the cursor at the desired location and click
the left mouse button. The component will be placed as in fig
29) In similar manner place the other two components (both
are RAD0.2) with a horizontal orientation (without pressing space bar in
step 27) as shown in fig 10.
The last two components placed are the capacitor and the diode, one of whose leads is connected to the ground. So one pad in each of these components should lie in the bottom later, tagged to ground.
Note: The pads place till now are multi-layered.
30) Select MAIN MENU --> EDIT --> PAD --> LAYER --> BOTTOM LAYER option to change the layer to the bottom layer.
31) Select MAIN MENU --> EDIT --> PAD --> POWER/GND --> TAGGED TO GROUND PLANE option to tag the pad to the ground plane.
Note: Use steps 11 through 16 as guidelines to edit a pad.
32) Repeat step 30 and step 31 for the other component also.
This completes the laying of components and pads on the PCB. The next step is to lay the tracks.
Note: Tracks are placed in the Bottom layer. If the current layer is not BOTTOM (the status bar should show a blue color indication if the bottom layer is selected) then change the current layer to bottom by following step 38, selecting BOTTOM LAYER instead of BOARD LAYER.
33) To place tracks, select MAIN MENU --> PLACE --> TRACK option.
34) Click on the intended starting and ending point of the track to be placed.
Note: Tracks should not bend at 90 degrees.
35) A track between one pad of the inductance and one pad of the vertical component (Capacitor) should be placed in four steps as shown in fig 11, fig 12, fig 13 & fig 14.
36) Repeat steps 33 through 35 to place tracks
for the required connections, as shown in fig 15
37) Last step of the design is to place a border for the board in the board layer.
38) To change to the Board layer (brown color indication in the status bar), select MAIN MENU --> CURRENT --> LAYER --> BOARD LAYER option.
39) Placing a border is nothing but placing four tracks to form a rectangle around the layout as shown in fig 16.
40) Fig 16 shows the final PCB layout.
This completes the design of the PCB for the circuit shown in fig 1. Following
this would be the configuring various settings to build the plot files
using the TRAXPLOT, ISOLATOR softwares. Finally the required
files are fed to the QCAM software,which controls the milling
machine, in milling the board.