Uses of Breadboard

A breadboard is used to make up temporary circuits for testing or to try out an idea. No soldering is required so it is easy to change connections and replace components. Parts will not be damaged so they will be available to re-use afterwards.

Almost all the Electronics Club projects started life on a breadboard to check that the circuit worked as intended.

The photograph shows a typical small breadboard which is suitable for beginners building simple circuits with one or two ICs (chips). Larger sizes are available and you may wish to buy one of these to start with.

Connections on Breadboard

Breadboards have many tiny sockets (called 'holes') arranged on a 0.1" grid. The leads of most components can be pushed straight into the holes. ICs are inserted across the central gap with their notch or dot to the left.

Wire links can be made with single-core plastic-coated wire of 0.6mm diameter (the standard size). Stranded wire is not suitable because it will crumple when pushed into a hole and it may damage the board if strands break off.

The diagram shows how the breadboard holes are connected:

The top and bottom rows are linked horizontally all the way across as shown by the red and black lines on the diagram. The power supply is connected to these rows, + at the top and 0V (zero volts) at the bottom.

I suggest using the upper row of the bottom pair for 0V, then you can use the lower row for the negative supply with circuits requiring a dual supply (e.g. +9V, 0V, -9V).

The other holes are linked vertically in blocks of 5 with no link across the centre as shown by the blue lines on the diagram. Notice how there are separate blocks of connections to each pin of ICs.

Large BreaboardsOn larger breadboards there may be a break halfway along the top and bottom power supply rows. It is a good idea

to link across the gap before you start to build a circuit, otherwise you may forget and part of your circuit will have no power!

Building a Circuit on Breadboard

Converting a circuit diagram to a breadboard layout is not straightforward because the arrangement of components on breadboard will look quite different from the circuit diagram.

When putting parts on breadboard you must concentrate on their connections, not their positions on the circuit diagram. The IC (chip) is a good starting point so place it in the centre of the breadboard and work round it pin by pin, putting in all the connections and components for each pin in turn.

The best way to explain this is by example, so the process of building this 555 timer circuit on breadboard is listed step-by-step below.

The circuit is a monostable which means it will turn on the LED for about 5 seconds when the 'trigger' button is pressed. The time period is determined by R1 and C1 and you may wish to try changing their values. R1 should be in the range 1k to 1M .

Time Period, T = 1.1 × R1 × C1

For further information please see 555   monostable .

IC pin numbers

IC pins are numbered anti-clockwise around the IC starting near the notch or dot. The diagram shows the numbering for 8-pin and 14-pin ICs, but the principle is the same for all sizes.

Components without suitable leads

Some components such as switches and variable resistors do not have suitable leads of their own so you must solder some on yourself. Use single-core plastic-coated wire of 0.6mm diameter (the standard size). Stranded wire is not

Monostable Circuit Diagram

suitable because it will crumple when pushed into a hole and it may damage the board if strands break off.

Building the example circuit

Begin by carefully insert the 555 IC in the centre of the breadboard with its notch or dot to the left.

Then deal with each pin of the 555:

1. Connect a wire (black) to 0V.

2. Connect the 10k resistor to +9V. Connect a push switch to 0V (you will need to solder leads onto the switch)

3. Connect the 470 resistor to an used block of 5 holes, then... Connect an LED (any colour) from that block to 0V (short lead to 0V).

4. Connect a wire (red) to +9V. 5. Connect the 0.01µF capacitor to 0V.

You will probably find that its leads are too short to connect directly, so put in a wire link to an unused block of holes and connect to that.

6. Connect the 100µF capacitor to 0V (+ lead to pin 6). Connect a wire (blue) to pin 7.

7. Connect 47k resistor to +9V. Check: there should be a wire already connected to pin 6.

8. Connect a wire (red) to +9V.

Finally...

Check all the connections carefully. Check that parts are the correct way round (LED and 100µF capacitor). Check that no leads are touching (unless they connect to the same block). Connect the breadboard to a 9V supply and press the push switch to test the circuit.

If your circuit does not work disconnect (or switch off) the power supply and very carefully re-check every connection against the circuit diagram.

Monostable Circuit on Breadboard

Breadboards

Making prototype circuitsusing a solderless breadboard

Many people are confused the first time that they have to build a circuit. How to connect the components together? The easiest way to get started is by using a solderless breadboard. A breadboard is a tool for holding the components of your circuit, and connecting them together. It’s got holes that are a good size for hookup wires and the ends of most components, so you can push wires and components in and pull them out without much trouble.

At right is a typical breadboard. There are several rows of holes for components. The holes on the breadboard are separated by 0.1-inch spaces, and are organized in many short rows in the center, and in two long rows down each side of the board. The short horizontal rows in the middle are separated by a center divider.

The pattern varies from model to model; some breadboards have only one strip down each side (like this model from Radio Shack), others have multiple side rows, and so forth. The basic model, with many horizontal rows separated by a central divider and one or two long side rows, is what we’ll focus on.

On each side of the board are two long rows of holes, with a blue or a red line next to each row. All the holes in each of these lines are connected together with a strip of metal in the back. In the center are several short rows of holes separated by a central divider. All of the five holes in each row in the center are connected with a metal strip as well. This allows you to use the holes in any given row to connect components together. To see which holes are connected to which, take a multimeter and a couple of wires, set the multimeter to measure continuity, stick the two wires in two holes, and measure them with the multimeter. If the meter indicates continuity, then the two holes in question are connected.

This image of the back of a breadboard may help to clear up how the holes on the front of the board are connected. The backing of the board has been removed (don’t remove the backing on your own board! It will make the board useless) to expose the metal strips connecting the holes. You can clearly see the short strips in the center separated by the divider, and the long strips down the side. The detail photo to the right illustrates how the holes and strips are related.

The reason for the center divider is so that we can mount integrated circuit chips, like a microprocessor, on the

breadboard. IC chips typically have two rows of pins that we need to connect other components to. The center row isolates the two rows from each other, and gives us several holes connected to each pin, so we can connect other components.

When you start to put components on your breadboard, avoid adding, removing, or changing components on a breadboard whenever the board is powered. You risk shocking yourself and damaging your components.

At left is a typical use of a breadboard. We have an IC chip (in this case a BX-24 microcontroller) straddling the center divider, connected to several of the rows of middle holes. At the top, a 7805 5V DC voltage regulator is connected to three of the middle rows. The 7805 regulator is also connected to the side rows of pins. Its ground pin is connected to the blue rows of holes, and its +5V output is connected to the red rows of holes. This way, the red rows of holes can be used to supply 5V, and the blue holes allow us to connect to ground. Note how the BX-24 is grounded by connecting the row that its ground pin is in to the blue rows with a short green wire. It is also powered by connecting the row that its +5V pin is in to the red rows with a short red wire. Note also the LED and resistor connected to the BX-24′s bottom left pin (pin 12).

In this detail , you can see that the resistor and the LED are connected in series between the BX-24 and ground (the blue row). A second row of middle holes is used to connect the LED to the resistor. Compare it to this wrong detail . Can you see what’s wrong with the second circuit? The resistor is short circuited, because both of its ends are connected to the same row!

In the first detail above, you saw components connected in series, by connecting one end of one component to a row, the other end to a second row, one end of a second component to the second row as well, and the other end of the second component to a third row. Components can also be connected in parallel on a breadboard. At right, the three LED’s are connected in parallel using two rows. They are then connected to power and ground by connecting the rows to the red power row and the blue ground row.

Many options are possible using a breadboard, which is what makes them very

useful and convenient for building circuits. Once you understand which holes are connected to each other (and which ones are not), you can build any circuit very quickly.

It’s a good idea to keep your circuits neat. When possible, shorten the leads on components so there is no bare metal sticking up from the breadboard. Make sure no wires cross each other with metal touching (this is the biggest source of short circuits on a breadboard). Lay things out as sensibly as possible, so each component of the circuit is near the components it needs to connect to. Use wires when needed to separate parts of the circuit that are crowded together. Use consistent colors of wires when possible; for example, use green or black for ground connections, red for power connections, white or blue for data connections, and so forth. This will make your troubleshooting much easier.

Building simple resistor circuits

In the course of learning about electricity, you will want to construct your own circuits using resistors and batteries. Some options are available in this matter of circuit assembly, some easier than others. In this section, I will explore a couple of fabrication techniques that will not only help you build the circuits shown in this chapter, but also more advanced circuits.

If all we wish to construct is a simple single-battery, single-resistor circuit, we may easily use alligator clip jumper wires like this:

Jumper wires with "alligator" style spring clips at each end provide a safe and convenient method of electrically joining components together.

If we wanted to build a simple series circuit with one battery and three resistors, the same "point-to-point" construction technique using jumper wires could be applied:

This technique, however, proves impractical for circuits much more complex than this, due to the awkwardness of the jumper wires and the physical fragility of their connections. A more common method of temporary construction for the hobbyist is the solderless breadboard, a device made of plastic with hundreds of spring-loaded connection sockets joining the inserted ends of components and/or 22-gauge solid wire pieces. A photograph of a real breadboard is shown here, followed by an illustration showing a simple series circuit constructed on one:

Underneath each hole in the breadboard face is a metal spring clip, designed to grasp any inserted wire or component lead. These metal spring clips are joined underneath the breadboard face, making connections between inserted leads. The connection pattern joins every five holes along a vertical column (as shown with the long axis of the breadboard situated horizontally):

Thus, when a wire or component lead is inserted into a hole on the breadboard, there are four more holes in that column providing potential connection points to other wires and/or component leads. The result is an extremely flexible platform for constructing temporary circuits. For example, the three-resistor circuit just shown could also be built on a breadboard like this:

A parallel circuit is also easy to construct on a solderless breadboard:

Breadboards have their limitations, though. First and foremost, they are intended for temporary construction only. If you pick up a breadboard, turn it upside-down, and shake it, any components plugged into it are sure to loosen, and may fall out of their respective holes. Also, breadboards are limited to fairly low-current (less than 1 amp) circuits. Those spring clips have a small contact area, and thus cannot support high currents without excessive heating.

For greater permanence, one might wish to choose soldering or wire-wrapping. These techniques involve fastening the components and wires to some structure providing a secure mechanical location (such as a phenolic or fiberglass board with holes drilled in it, much like a breadboard without the intrinsic spring-clip connections), and then attaching wires to the secured component leads. Soldering is a form of low-temperature welding, using a tin/lead or tin/silver alloy that melts to and electrically bonds copper objects. Wire ends soldered to component leads or to small, copper ring "pads" bonded on the surface of the circuit board serve to connect the components together. In wire wrapping, a small-gauge wire is tightly wrapped around component leads rather than soldered to leads or copper pads, the tension of the wrapped wire providing a sound mechanical and electrical junction to connect components together.

An example of a printed circuit board, or PCB, intended for hobbyist use is shown in this photograph:

This board appears copper-side-up: the side where all the soldering is done. Each hole is ringed with a small layer of copper metal for bonding to the solder. All holes are independent of each other on this particular board, unlike the holes on a solderless breadboard which are connected together in groups of five. Printed circuit boards with the same 5-hole connection pattern as breadboards can be purchased and used for hobby circuit construction, though.

Production printed circuit boards have traces of copper laid down on the phenolic or fiberglass substrate material to form pre-engineered connection pathways which function as wires in a circuit. An example of such a board is shown here, this unit actually a "power supply" circuit designed to take 120 volt alternating current (AC) power from a household wall socket and transform it into low-voltage direct current (DC). A resistor appears on this board, the fifth component counting up from the bottom, located in the middle-right area of the board.

A view of this board's underside reveals the copper "traces" connecting components together, as well as the silver-colored deposits of solder bonding the component leads to those traces:

A soldered or wire-wrapped circuit is considered permanent: that is, it is unlikely to fall apart accidently. However, these construction techniques are sometimes considered too permanent. If anyone wishes to replace a component or change the circuit in any substantial way, they must invest a fair amount of time undoing the connections. Also, both soldering and wire-wrapping require specialized tools which may not be immediately available.

An alternative construction technique used throughout the industrial world is that of the terminal strip. Terminal strips, alternatively called barrier strips or terminal blocks, are comprised of a length of nonconducting material with several small bars of metal embedded within. Each metal bar has at least one machine screw or other fastener under which a wire or component lead may be secured. Multiple wires fastened by one screw are made electrically common to each other, as are wires fastened to multiple screws on the same bar. The following photograph shows one style of terminal strip, with a few wires attached.

Another, smaller terminal strip is shown in this next photograph. This type, sometimes referred to as a "European" style, has recessed screws to help prevent accidental shorting between terminals by a screwdriver or other metal object:

In the following illustration, a single-battery, three-resistor circuit is shown constructed on a terminal strip:

If the terminal strip uses machine screws to hold the component and wire ends, nothing but a screwdriver is needed to secure new connections or break old connections. Some terminal strips use spring-loaded clips -- similar to a breadboard's except for increased ruggedness -- engaged and disengaged using a screwdriver as a push tool (no twisting involved). The electrical

connections established by a terminal strip are quite robust, and are considered suitable for both permanent and temporary construction.

One of the essential skills for anyone interested in electricity and electronics is to be able to "translate" a schematic diagram to a real circuit layout where the components may not be oriented the same way. Schematic diagrams are usually drawn for maximum readability (excepting those few noteworthy examples sketched to create maximum confusion!), but practical circuit construction often demands a different component orientation. Building simple circuits on terminal strips is one way to develop the spatial-reasoning skill of "stretching" wires to make the same connection paths. Consider the case of a single-battery, three-resistor parallel circuit constructed on a terminal strip:

Progressing from a nice, neat, schematic diagram to the real circuit -- especially when the resistors to be connected are physically arranged in a linear fashion on the terminal strip -- is not obvious to many, so I'll outline the process step-by-step. First, start with the clean schematic diagram and all components secured to the terminal strip, with no connecting wires:

Next, trace the wire connection from one side of the battery to the first component in the schematic, securing a connecting wire between the same two points on the real circuit. I find it helpful to over-draw the schematic's wire with another line to indicate what connections I've made in real life:

Continue this process, wire by wire, until all connections in the schematic diagram have been accounted for. It might be helpful to regard common wires in a SPICE-like fashion: make all connections to a common wire in the circuit as one step, making sure each and every component with a connection to that wire actually has a connection to that wire before proceeding to the next. For the next step, I'll show how the top sides of the remaining two resistors are connected together, being common with the wire secured in the previous step:

With the top sides of all resistors (as shown in the schematic) connected together, and to the battery's positive (+) terminal, all we have to do now is connect the bottom sides together and to the other side of the battery:

Typically in industry, all wires are labeled with number tags, and electrically common wires bear the same tag number, just as they do in a SPICE simulation. In this case, we could label the wires 1 and 2:

Another industrial convention is to modify the schematic diagram slightly so as to indicate actual wire connection points on the terminal strip. This demands a labeling system for the strip itself: a "TB" number (terminal block number) for the strip, followed by another number representing each metal bar on the strip.

This way, the schematic may be used as a "map" to locate points in a real circuit, regardless of how tangled and complex the connecting wiring may appear to the eyes. This may seem excessive for the simple, three-resistor circuit shown here, but such detail is absolutely necessary for construction and maintenance of large circuits, especially when those circuits may span a great physical distance, using more than one terminal strip located in more than one panel or box.

REVIEW: A solderless breadboard is a device used to quickly assemble temporary circuits by plugging

wires and components into electrically common spring-clips arranged underneath rows of holes in a plastic board.

Soldering is a low-temperature welding process utilizing a lead/tin or tin/silver alloy to bond wires and component leads together, usually with the components secured to a fiberglass board.

Wire-wrapping is an alternative to soldering, involving small-gauge wire tightly wrapped around component leads rather than a welded joint to connect components together.

A terminal strip, also known as a barrier strip or terminal block is another device used to mount components and wires to build circuits. Screw terminals or heavy spring clips attached to metal bars provide connection points for the wire ends and component leads, these metal bars mounted separately to a piece of nonconducting material such as plastic, bakelite, or ceramic

Using A Solderless Breadboard

© 2010 By Small Bear Electronics LLC

This article is meant for the beginning stompbox builder who wants to learn how a solderless breadboard works and how to use it for prototyping. As a matter of necessity, I'll also show some basic functions of using a multimeter for continuity and voltage tests and introduce interpreting a schematic. From that point, subsequent articles will cover setting up various effect circuits.

Why A Breadboard?

So you have come up with a pinky-new circuit for the World's Greatest Distortion/Trem/Delay, etc., etc. that will have guitar players worldwide salivating to put one in their effects loop. You engineer everything carefully, build with super high-quality components and fire it up. Of course, either:

It doesn't work. Or It works, but it doesn't sound "right."

The solderless breadboard provides a way to set up a circuit for testing purposes without committing to a permanent build. It's the electronic equivalent of a kid's Erector set; components can easily be added or removed, and whole sections can be reconfigured as many times as necessary to get to a finished design.

The model that I use in this article:

is typical of many that are available from mail-order shops, as well as from Radio Shack in the U.S. More complex and expensive versions exist, some of which include built-in power supplies and mounting brackets for controls. On the other hand, if you are on a very tight budget, you can buy only the plastic rail (often called a "breadboard strip") without the metal base. Bottom line: My directions will mostly be applicable to anything you buy, whether from my Stock List or anywhere else.

How It Works - The "Bear Bones"

Within each hole in the plastic rail is a spring-loaded contact that will positively grip the lead of a component that you insert, but still allow you to remove it easily. Each column of five holes is connected internally (Fig. 1). It may help you get oriented by actually satisfying yourself that this is the case. Insert short lengths of bare #22 or #24 wire into any two holes in a column (Fig. 2).

Now set the selector of your multimeter to the Continuity position (or the lowest resistance scale if your instrument does not have a Continuity position) and measure between the wires (Fig. 3).

OK so far? Many breadboards have

Busses

A bus (in this case) is a row of holes connected horizontally so that power can easily be distributed to the points in the circuit where it is needed, and/or to provide a common ground. (I'll get more into that concept and define it later.) This breadboard has two busses (Fig. 4):

I have outlined them in the pic to show how they are connected. By all means, do the test with the multimeter if you need to to be sure that you know what is--and is not--connected to what. While each bus in this breadboard is connected all the way across, I have seen models in which the bus is split in the middle; you have to connect the two halves together if you want continuity across the full length.

You have probably noticed that the rows on each strip have letters and the columns are numbered. This is sometimes useful for referring to specific locations, as we'll do later on.

Making Connections

Let's begin by setting up a very simple circuit just to light an LED. This will demonstrate a couple of necessary points before we tackle an effect. This breadboard has red (+) and black (-) binding posts for connecting power, but I usually use a 9-volt battery snap to which I have soldered a couple of plug-in leads. It's very easy to make.

First, cut a couple of pieces of #22 or #20 bare wire about 1/2" long. Wrap a few turns of the end of each battery lead around one of the pieces and solder (Fig. 5.) (I will talk about where to find/buy connecting wire for the breadboard in a minute.) Cover the solder joints with small pieces of 1/16" heat shrink, and conform the tubing to the joint by rubbing it gently with the barrel of your soldering iron Then put a right-angle bend in each end, and you have a connector (Fig. 6.) It plugs conveniently into the busses of the breadboard (Fig. 7.)

Shown as a schematic, here is what we want to connect:

Pretty simple, right? A schematic shows the logical connection of components, but not necessarily the physical way that they are laid out. So let's lay this out on the breadboard. First, cut off half the leads from a 10K resistor (Brown, Black, Orange, Gold) and save the wire scraps for use later. Bend the leads flush to the body, and plug the resistor into any two convenient columns (Fig. 9); breadboarding is pragmatic and practical and does not have many fixed rules about what goes where. The LED is a diode by definition and so is polarized (Fig. 10.) Plug it in with its positive lead in the same column as the right-hand lead of the resistor (Fig. 11.) You have made the connection shown in Fig. 12. Got the idea?

Now finish the circuit. Create a couple of jumpers from #22 or #24 bare stock (Fig. 13) and plug these in to make the connections to the power supply busses (Fig. 14.) Connect the battery (Fig. 15) and let there be light!

A few notes:

For purposes of illustration, I squared the corners of the jumpers and made the hole-to-hole lengths exact, but neither is necessary for routine work; as I noted earlier, breadboarding is pragmatic and based on speed and convenience.

Jumpers can be made from insulated or bare wire. Use insulated wire where there is any possibility that leads will short.

Wire for making jumpers can be bare or tinned copper, and most breadboards will accommodate gauges from #20 to #24. You can find suitable material in Wire and Cable on my Stock List or from other stores, but you can also take advantage of free sources: Save the scraps of wire that result when you trim component leads; many of these are perfect for jumpers that need to span only two or three holes. Also, if you run across a job

site where telephone installation or removal is being done, look out for discarded pieces of multi-pair cable that contain as many as 50 of these individual conductors (Fig. 16):

Slice the outer jacket, remove a bunch of these wires, and you will have all you need for many moons of experiments.

Are you ready to Rock and Roll? OK!!

At this point, you can proceed to the article on Breadboarding A Silicon Fuzz Face. I will add other effects to this series down the road. Welcome, and let the Noise begin!