Your own board

A printed circuit board starts as parts on a grid and a list of nets: pads that must end up joined. Thin ratsnest lines show the joins still to make. Students find nets, then move and turn parts so the joins are short and the connector sits at the edge.

1. Where to put the parts
2. Try: nets and moves › A net
3. Try: nets and moves › Count the pads
4. Try: nets and moves › Move a part
5. Worked example: read the board › Placement, step by step
6. Worked example: read the board › Why the edge?
7. Vary: meet the brief
8. Practise: placement › Millimetres
9. Practise: placement › Joins
10. Practise: placement › Gaps
11. A smaller board › A small board
12. A smaller board › Evaluate

Routing turns every ratsnest line into copper. Two traces of different nets can never touch, so where they must cross, one goes round or drops to the other side of the board. Students route the shield on one layer, then on two, and compare the copper.

1. Crossing
2. Try: route on the top › VCC
3. Try: route on the top › OUT, then GND
4. Try: route on the top › What happened?
5. Worked example: round or under? › Two ways past OUT
6. Worked example: round or under? › When you need a via
7. Vary: one side only
8. Practise: routing › Short
9. Practise: routing › Via
10. Practise: routing › Copper
11. Route it short › Short copper
12. Route it short › Evaluate

A trace that carries a motor's current must be wider than one that carries a signal, or it heats up. Students set trace widths against current, meet a trace too wide to pass between pins, then work out what an order of boards costs.

1. Which trace burns?
2. Try: set the widths › Widths
3. Try: set the widths › Why not wide?
4. Worked example: width from current › Choose the width
5. Worked example: width from current › Two rules meet
6. Vary: a squeeze
7. Practise: rules and orders › Width
8. Practise: rules and orders › An order
9. Practise: rules and orders › Per board
10. Ready to order › Pass the rules
11. Ready to order › Order
12. Ready to order › Evaluate