Electronic design and Construction

The first and foremost thing to consider is the design of your electronics. This lesson will deal with products and ideas to make your design and construction a lot more simple.

Solderless Breadboards

Solderless breadboards are used to experiment with your circuitry. They are not used for permanent circuits. Doing this before making a permanent circuit will allow you to change your design or improve its performance by just removing or adding a component.

Printed Circuit Boards

You can buy premade circuit boards, or you can make your own. Either way, once you have worked your design out on a breadboard, you can permanently build your circuit on a PCB.

Wire Gauge

Wire comes in different sizes. 30 AWG gauge wire is small and its maximum current capacity is 2 amps, while 12 AWG gauge wire is large and its MCC is 36 amps. The smaller the wire, the less current it will allow before overheating and burning up.

Eliminating Static Electricity

It has been said that your body walking across a carpet can develop a 10,000 to 50,000-volt charge. What would that do to a 5-volt component? COMPLETELY DESTROY IT! When working on your electronics, use an antistatic mat and wear low static clothes such as cotton. Store parts in antistatic pouches or tubes. Sometimes connecting an antistatic wrist strap to your wrist and the component works to eliminate static. Also, make sure your soldering iron is grounded.

Good Design Principles

  • Even though a device may be unplugged, there is still a small amount of current flowing in the device. A pull-up resistor between the input and the +V (positive voltage) supply or a pull-down resistor (10k for either) between the input and ground will prevent this from happening.

  • Unless instructed not to, tie unused inputs to ground to keep the circuit from going into oscillation.

  • Bypass capacitors at the +V and ground terminals of every integrated circuit will reduce noise. For this, a 10 µF capacitor will do.

  • Keeping lead lengths short by snipping them close to the solder joint will keep noise down and prevent the lead from acting like an antenna.

  • Make sure your +V and ground wires never form a loopor noise and erratic behavior will occur.

Soldering Tips and Techniques

The best tip that can be given is to get yourself a good soldering "station", not just the iron. You may save yourself money by getting the whole kit. In the kit, like the ones you may find at WellerSears (under Tools > Electrical Shop > Soldering Tools & Accessories), or online at All-Spec, you'll find a soldering iron, an adjustable temperature base with a side tray for a sponge, the sponge, and a holder to keep your iron from burning anything. You can find these as low a $50 if you look, less at rummage sales. You need to use 0.050 inch rosin core solder only. Needle-nose pliers, wire strippers, wire cutters, and a heat sink are good tools to have. Isopropyl alcohol is a necessity to clean your components as well as your solder and iron. In case of a bad solder job or you are harvesting and you want to desolder the joints, a solder vacuum comes in handy.

As for how to solder, you may hear different ways of doing it, but the most important part is making a solid joint with just enough solder. To do this, you want to heat the joint with the iron and apply the solder. In some cases, you may not be able to hold the iron on the joint to heat it while you apply the solder. In this case, heat the joint for a second, lift, touch the solder to the joint, then the iron to the solder. In either case, use a multitester or ohm meter to make sure you made a good connection. Also, give the joint a slight tug. If it stays in tact, you've completed a solid joint. Make sure you are soldering in a well-ventilated area. Also, always wear eye protection and keep a fire extinguisher handy, just in case.

The first and foremost thing to consider is the design...
Next: Plastic platform construction