Fun with solderless breadboards When building a circuit for the first time* it is often very useful to have a way to quickly change connections or parts placement. In the early days of electronics* quick* temporary circuits were sometimes built on a piece of wood* similar to the boards that bread is sliced on. Building a first prototype came to be known as breadboarding. Back when components like tubes and transformers were large and long wires were common* it was easy to solder and unsolder connections. Modern circuits* made with small transistors or many legged integrated circuits* are much harder to solder and especially to unsolder. To make life easier* solderless breadboards were invented. These are blocks of plastic with holes into which wires can be inserted. The holes are connected electrically* so that wires stuck in the connected holes are also connected electrically. The connected holes are arranged in rows* in groups of five* so that up to five parts can be quickly connected just by plugging their leads into connected holes in the breadboard. When you want to rearrange a circuit* just pull the wire or part out of the hole* and move it or replace it. In the photo above* we have a complete radio* with an antenna coil* a tuning capacitor* a three-legged integrated circuit* a battery* and earphone* two resistors* and three capacitors. This radio is the Three Penny Radio kit from the Scitoys Catalog* which is usually soldered* using three pennies as convenient places to connect the various parts. The three-penny radio needs these parts: An antenna coil You can wind one by hand* but in this project we use a much smaller coil with a ferrite rod inside* from our catalog. An MK484-1 AM Radio Integrated Circuit This is the heart of the radio. We carry it in our catalog. A Piezoelectric earphone Also in our catalog. A tuning capacitor We use a variable capacitor* from 0 to 160 microfarads. We have it in our catalog. A 100*000 ohm resistor This resistor will have four colored bands on it. The colors will be brown* black* yellow* and gold. A 1*000 ohm resistor This resistor will also have four colored bands on it. The colors will be brown* black* red* and gold. A 0.01 microfarad capacitor This capacitor will be marked something like ".01M" or "103". Two 0.1 microfarad capacitors These capacitors will be marked something like ".1M" or "104". A 1.5 volt battery A 1.5 volt battery holder And* in this version: A solderless breadboard Also in our catalog. and later: A printed circuit board Also in our catalog. In the closer view* you can see that the parts we want to be electrically connected are plugged into one of the five holes marked A* B* C* D* or E* (or in this case* where we used the second half of the board* marked F* G* H* I and J) in rows marked 1 through 63. Along each side of the breadboard are two strips of power supply rails* making it convenient to connect a battery when many parts need power. In our simple radio* only one part needs power* so it is convenient to simply plug the battery wires directly into the main circuit area. The solderless breadboard is designed to accept the leads from parts such as resistors* integrated circuits* transistors* and other parts with round solid wire for leads. Some of the parts for the radio have thin* stranded wire that is not stiff enough to poke into the holes* or (like the variable capacitor) have flat strips of metal that are too big to fit into the holes. For these parts* we solder their leads to pieces of wire cut from the leads of other parts* such as resistors or capacitors. Most such parts have leads that are longer than we needed anyway* so they will fit more snuggly onto the board with shorter leads. In the photo you can see that the antenna coil* the variable capacitor* and the piezoelectric earphone have wires soldered to their leads to make it easy to plug them into the breadboard Having the holes arranged in a labeled grid is convenient for describing the parts layout. We can list each part* and the letter and number of each lead: Antenna coil: J9 and G16 Tuning capacitor: F9 and F16 (only the two rightmost leads are used) MK484 IC: H15* H16* and H17 (flat side facing row G) 100*000 ohm resistor( brown* black* yellow): I9 and J17 1*000 ohm resistor (brown* black* red): I17 and I20 0.01 microfarad capacitor (marked 103 or .01M): G9 and G15 0.1 microfarad capacitor (marked 104 or .1M): F15 and F17 0.1 microfarad capacitor (marked 104 or .1M): F17 and F22 Piezoelectric earphone: F20 and F22 Negative battery wire (black): J15 Positive battery wire (red): J20 This makes it very simple to build the circuit* and easy to double check all of the connections. Making the circuit permanent Solderless breadboards are great for building circuits the first time* and getting them to work* or experimenting with design changes. But when you get the circuit working the way you want it to work* you will want to copy it to a more permanent form* by soldering it onto a circuit board. The printed circuit boards we carry in our catalog also have five holes that are electrically connected. The holes are grouped into 3 holes and 2 larger holes* to make it convenient to connect larger wires leading out from the board* for power connections and other external parts. The radio shown below was built by a student as a first exercise in soldering Here is the back side It worked the first time!