1. LSU 08/11/2004Electronics 31 Introduction to Electronics Electronics Unit, Lecture 3

2. LSU 08/11/2004Electronics 32 Prototyping Techniques and Soldering Electronics Unit – Lecture 3 Schematic Diagrams Assembly Methods Soldering Tutorial

3. LSU 08/11/2004Electronics 33 Schematic Diagrams Schematic diagrams represent an electronic circuit in symbolic form. A schematic need not depict the actual physical arrangement of the components

4. LSU 08/11/2004Electronics 34 SkeeterSat Schematic

5. LSU 08/11/2004Electronics 35 Component Symbols Wires and wire connections Current practice: Either A or B is acceptable C is the preferred style D is seldom used E is interpreted as a non-connection

6. LSU 08/11/2004Electronics 36 Component Symbols Power sources (V) and common connections (GND)

7. LSU 08/11/2004Electronics 37 Component Symbols Resistors (R) and Capacitors (C)

8. LSU 08/11/2004Electronics 38 Component Symbols Inductors (L) and Transformers (T) simple inductors transformers The two parallel lines indicate that the inductor is wound on a core of iron, iron powder, or ferrite material. adjustable tapped

9. LSU 08/11/2004Electronics 39 Component Symbols Diodes (D) The arrow points in the allowed direction of conventional (positive charges) current flow. The bar represents the cathode, marked with a band on most parts.

10. LSU 08/11/2004Electronics 310 Component Symbols Transistors (Q) bipolar NPN junction transistor bipolar PNP junction transistor N-channel junction field-effect transistor P-channel junction field-effect transistor N-channel MOS field-effect transistor P-channel MOS field-effect transistor

11. LSU 08/11/2004Electronics 311 Component Symbols Integrated circuits (U) Most complex integrated circuits are represented on schematic diagrams as a rectangular block symbol, with pin numbers and, usually, pin functions indicated; but many logic integrated circuits have special symbols that identify their function.

12. LSU 08/11/2004Electronics 312 Component Symbols Switches (S) and Relays (K) single pole single throw SPST single pole double throw SPDT double pole single throw DPST double pole double throw DPDT rotary switch 1 pole, 5 position single pole double throw relay

13. LSU 08/11/2004Electronics 313 Component Symbols Miscellaneous Components and Devices

14. LSU 08/11/2004Electronics 314 Drawing Schematic Diagrams Use one of the many schematic capture programs available on the WWW for free download, for example: ExpressPCB http://www.expresspcb.com/http://www.expresspcb.com EagleLite http://www.cadsoftusa.com/freeware.htmhttp://www.cadsoftusa.com/freeware.htm These usually include printed circuit board layout capability as well. The SkeeterSat schematic shown earlier was prepared with ExpressPCB

15. LSU 08/11/2004Electronics 315 Building a prototype Solderless breadboards Perfboards or Protoboards Manhattan Construction Dead Bug Construction Etched Circuit Boards

16. LSU 08/11/2004Electronics 316 Solderless Breadboards The term breadboard originated in the early days of radio, when many experimenters actually built circuits on the wooden boards used in their mother’s kitchen for rolling out bread dough. modern solderless breadboards Best thing to come along since sliced bread! A ham radio transmitter circa 1930

17. LSU 08/11/2004Electronics 317 Perfbord or Protoboard Components are soldered to the board, with connections made using a combination of short pieces of wire and the copper traces already present on some versions of these boards.

18. LSU 08/11/2004Electronics 318 Manhattan and Dead Bug Construction

19. LSU 08/11/2004Electronics 319 Etched Circuit Boards

20. LSU 08/11/2004Electronics 320 Soldering Tutorial Soldering – fastening metal objects using molten metal (solder) as the glue. Three requirements Low melting point metal (wire solder) Heat source (soldering iron) Flux (to prevent surfaces from oxidizing)

21. LSU 08/11/2004Electronics 321 Types of Solder Tin-Lead solders 60% Tin, 40% Lead - solid at 361° F, liquid at 374° F 63% Tin, 37% Lead - eutectic point is 361° F no “pasty” range so joint movement less a problem Silver-bearing Solder 62% Tin, 36% Lead, 2 % Silver - solid at 354 ° F, liquid at 372 F often used for surface mount components whose contacts contain trace amounts of silver

22. LSU 08/11/2004Electronics 322 Soldering Irons Constant wattage Iron is continuously “ON” and eventually reaches equilibrium temperature 20 to 25 watt iron sufficient for circuit board assembly Constant temperature Tip incorporates a thermostatic element to maintain desired tip temperature 650 – 750 ° F appropriate for circuit board assembly But wait…..even better… Weller® 30 watt iron

23. LSU 08/11/2004Electronics 323 Soldering Irons Temperature Controlled Solder Station Feedback control maintains tip at desired temperature Adjustable, often with analog or digital temperature display Many have grounded tip to help prevent ESD damage Weller® solder station

24. LSU 08/11/2004Electronics 324 Types of Flux Rosin Flux Type R – ordinary rosin – most common Type RMA – mildly activated rosin Type RA – activated rosin – use with care Acid Flux – NEVER, EVER use this for electronics

25. LSU 08/11/2004Electronics 325 Flux-core solder Most solder used for electronics assembly is in wire form, with the flux incorporated inside the solder. Multi-core solder has several (usually five) separate flux channels within the solder. For circuit board assembly use wire solder with a diameter of about 0.025 inch or less

26. LSU 08/11/2004Electronics 326 Soldering a Component Use a lead bending jig, if available, to form the component leads to the correct spacing If a bending jig is not on hand, grasp the leads, not the body, of the component with needle-nosed pliers and bend gently.

27. LSU 08/11/2004Electronics 327 Soldering a Component Insert the component’s leads through the holes in the circuit board. The body should lie flat against the board without having to force it down. Turn the board over and gently bend the component leads outward to hold the component in place

28. LSU 08/11/2004Electronics 328 Soldering a Component Clean the iron tip by wiping on a damp sponge. Tin the tip by applying solder, then wipe again. Apply the iron in contact with both the circuit board pad and the component lead. Apply solder to the joint, not to the iron, and allow the heated joint to melt the solder QT Movie Clip

29. LSU 08/11/2004Electronics 329 Soldering a Component Use a pair of flush-cutting wire cutters to cut off the excess lead length as close to the board as possible. Hold the lead so will not fly away when cut, a possible occasion for eye injury. !! WEAR SAFETY GLASSES !! Inspect the soldered and trimmed lead. It should be uniform and shiny, with no cracks, gaps, or graininess. Good soldering Bad soldering QT Movie Clip

30. LSU 08/11/2004Electronics 330 Activities E3a.Use the supplied assortment of components and practice soldering them to the perfboard. E3b. Locate each SkeeterSat component on the schematic diagram, and then on the circuit board layout. Be careful to note if the part has to be oriented in a special way. You will actually construct your SkeeterSat in the next session.