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Electronics
Discrete Components
- Resistors
- Capacitors
- Inductors
Semiconductors
Power
- [Batteries]
Electrical
Pages pertaining to house and automotive electrical systems
Microcontrollers
Pages about small computers, programming and process control
Circuit Design Tips
1. Use existing circuits as building blocks to form entirely new circuits.
2. Always review the manufacturers specifications for active devices (transistors, integrated circuits etc.) before using them in a circuit. Pay particular attention to operating voltages and potential problems such as oscillation, noise, catchup etc.)
3. Bypass capacitors, while not always required, can prevent noise and oscillation in analogue circuits and false triggering and memory loss in digital circuits. In analogue circuits place a 0.1uF and 1.0uF capacitor across battery leads where they enter the circuit board. Use 0.1uF capacitors from power supply pins of operational amplifiers to ground. In digital circuits place a 0.1uF capacitor across the power supply pins of each chip.
4. Component substitution is generally OK. Here are some general guidelines:
4a. Resistors - Use next closest value. Use equal or higher power rating. Circuit performance may be altered. For example, a smaller than specified resistor in series with an LED will increase current through the LED.
4b. Capacitors - Use the next closest value. Use equal or higher voltage rating. Circuit performance may be altered. For example, using a smaller than specified capacitor in a timing circuit will reduce the timing cycle.
4c. Bipolar transistors - Substitute within the same family. Observe polarity and power.
Circuit layout tips
1. Conections between components should be as short as possible in high speed digital circuits and high frequency analogue circuits.
2. The input and output sections of high gain amplifiers should be physically isolated from one another. Otherwise inductance between the input and output wiring may cause a portion of the output signal to be fed back to the input. The result will be severe oscillation.
3. Power Transistors, ICs and some other components that become warm during operation often perform better with a hear sink. Therefore leave space around such components for a heat sink. Avoid placing heat sensitive components near components that may become hot.
4. Use insulated wire for interconnections. Insulate exposed component leads mounted close to other exposed leads or hardware.
5. All leads that carry household line currents must be insulated.
6. Circuits in which a current flow is suddenly switched off or on may emit radio frequency radiation that can cause significant interference in nearby radios and televisions. Radio frequency emissions can be reduced by enclosing the entire circuit in a grounded metal enclosure. External connections to or from the enclosure should be made with shielded cables.
7. Use stranded wire for all connections that are not fixed in position (battery clip leads etc.) Use solid wire for fixed connections.
Soldering
Follow these steps to produce successful solder connections:
1. Electronic components and circuit boards can be damaged by excessive heat. Therefore when soldering components to a board, always use a low wattage (15w - 40w) or preferably temperature controlled soldering iron. Be sure to tin the tip according to the instructions supplied with the iron. Whet the tip of the iron with solder to improve heat transfer.
2. Always use small diameter rosin core solder (or equivalent) when soldering small parts. Never use acid core solder. It will corrode the soldered leads.
3. Always prepare the surfaces to be soldered. Solder will not adhere to paint, oil, wax, grease or melted insulation. Remove these materials with a solvent, steel wool or fine sandpaper. Always buff the copper foil of a circuit board with steel wool. Be sure there is a good connection between surfaces being soldered.
4. To solder, hear the connection first, not the solder. After a second or two touch the end of a length of solder to the connection so that the solder melts onto the connection not onto the iron.
5. Leave the hot tip of the iron in place until molten solder flows through and around the connection. Then remove the iron. IMPORTANT: Do no apply too much solder or allow the connection to move before it has cooled enough to solidify.
6. Keep the tip of the iron clean and shiny. Wipe away excess solder and debris with a damp silicone sponge or cloth.
Desoldering
A component can be removed from a board by heating its connections with a hot soldering iron until the solder melts and then pulling on the leads of the component until it is free. Unless specialised desoldering tips are used this method is suitable only for individual wires of components with two leads. To remove components with multiple leads or pins, desoldering braid, a desolder pump or desoldering iron can be used to remove solder from the board allowing the pins to become free before removing the component. Use the manufacturers instructions for these methods.
Soldering precautions
1. A hot soldering iron can cause a fire or burn flesh. Unplug an unused soldering iron.
2. Avoid breathing in smoke and vapour from hot soldering. Solder in a well ventilated area or use a fume extractor or filter.
3. Supervise children who use soldering irons.