My name is Jeremy, and I am in my junior year at Kettering University. As a student of Electrical Engineering, I have had the opportunity to spend many hours in labs building small circuits on breadboards. If you are experienced with making small circuits and do-it-yourself electronics projects, you may not find much beneficial here. The purpose of this instruction is to cover the basics of using a breadboard, introduction to common components, and building small circuits. Additionally, I will briefly discuss how to organize your circuit, as well as some troubleshooting strategies for those occasions when things go awry.
It is assumed that the individual reading this has some familiarity with the basics of electronics and terminology: current flow, voltage, polarity, conductance, short-circuit, open-circuit, junction, and bias. Additionally, it is assumed the reader is familiar with switching power supplies used in the lab environment.
I am writing this because I enjoy building small circuits in the labs and have observed some common issues and errors along the way. My hope is that this will help someone just embarking on their journey into the discovery of electronics to find something useful that will save them some of the headaches I have encountered along the way, and open the door to the joys of small circuit building!
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Step 1: The Breadboard
What is a breadboard?:
A popular tool for prototyping and testing circuits, allowing the user to quickly connect and swap out components and make junctions with ease. Using a breadboard allows rapid assembly and modification of circuits without soldering requirements.
- Terminal strips: Run horizontally, with row numbers incremented by five, and column letters in groups of five. Row 1, columns A-E make up one continuous contact point - or junction, and Row 1, columns F-J make up another.
- Bus strips:Run vertically in pairs down the length of each side, and are labeled either "+" or "-". The entire + strip is one continuous junction, and the - strip is a continuous junction, allowing many components to be connected to a power source.
- Trough / Groove: Runs the length of the breadboard vertically between the Terminal strips. The rows are discontinuous at this groove, allowing the use of Integrated Circuits(IC's).
Breadboards can be purchased in a variety of sizes and styles, but the above configuration description remains the same whether you have the half-breadboard , or a larger model with power terminals and multiple boards mounted to a metal plate.
In order to be successful in making your circuits, it is critical to have a firm grasp on the layout of the contact points in the breadboard. When employed properly, the breadboard is a great tool for building circuits and making modifications on the fly!
Step 2: Know Your Components
Within electronic circuit design, one will encounter a variety of components. While this is not intended to be an exhaustive list, I will highlight some of the more common components, their purpose, and some warning for handling. Many headaches can be saved by handling and using components properly. If you are just starting out in electronics, many components kits can be found to give you the basics for under $20.
Resistor: (measured in Ohms) Resists the flow of current within a circuit. Depending on placement within a circuit can be used to divide voltage or current. Resistors have colored bands on them which indicate their resistance value in ohms as well as their tolerance. A table is useful for determining the resistance values. A resistor can be placed in either direction within a circuit, and will function the same way (it does not have polarity).
Photo-Resistor: Resists the flow of current. The resistance value varies based on the ambient light. Can be used in dimming applications or turning on a circuit during low-light conditions.
Capacitor: (measured in Farads) A capacitor stores energy which can then be dissipated into a circuit at a later time. It acts as a block to direct current, but allows alternating current to pass through. Capacitors have a wide range of application from frequency filtration to smoothing ripples in a rectifier circuit. It is important to note that while ceramic disc capacitors are not polar components, care must be taken with electrolytic capacitors, as they have a designated lead for connection to the positive and negative terminals and can be damaged when place backwards.
Transistor: A transistor is a semiconductor which regulates current flow, amplifies signals, or acts as a switch. There are many different types of transistor, but the most important consideration in early circuit design (assuming you have the correct transistor for the application) is that care must be taken to avoid static shock to these components.
Diode: A Diode is a semiconductor which acts as a one-way check valve to current flow. When forward-biased, current enters the anode (+ lead) and flows out the cathode (- lead) . When reverse-biased, however, it acts as an open switch, and no current flows across the component. Consideration must be taken to the orientation, as placing a diode backward will result in undesirable circuit behavior, or a blown diode.
Light-Emitting Diode (L.E.D): A special diode which emits light when it is conducting. Used in many small applications where indicators are needed. Benefits include extremely low power consumption, and extremely long life.
Integrated Circuit: The last component on I will introduce is the integrated circuit (IC). There are far too many variations to list here, but a few are the operational amplifier, timers, voltage regulators, and logic arrays. Integrated circuits provide an entire circuit within a small chip, and can contain resistors, diodes, capacitors, and transistors all within a chip smaller than a dime. There is a numbering convention for the pins on an IC chip, there is an indent, or dot on the surface of the chip, and this corresponds to pin #1, the pins are then sequentially numbered down the side, and back up the other.
CAUTION! Integrated circuits can be destroyed from static shock.
Along with the above components, there are inductors, relays, switches, potentiometers, variable resistors, seven-segment displays, fuses, transformers... you get the idea! A quick online search will provide a lot of useful information (For example: overviews of components , what does a transistor do?, types of capacitors)
Knowing the basic information about the components you are using, whether or not they are static-sensitive, and whether or not they have polarity will be greatly beneficial. Not only will you save time, money, and headache; but the circuit will be more likely to function as desired much more quickly!
Step 3: Organization Is Essential
Organization - Why does it matter? :
The above circuits (Right-hand side) are the same functionally, but with notably different appearance. While the first uses less wiring, it is not the preferred method for building small circuits. There is plenty of room on a breadboard for small circuits; don't be afraid to utilize this space!
While choice of what to use for leads is personal, a couple of things can make life significantly easier. A lot of people will use copper wire and make their own leads, but my preference is the breadboard jumpers which can be purchased cheaply online. The jumpers are made of strands of wire versus the stiff copper wire, and have a pin on the end for easy use. The advantage with the strands, is that the wiring is much more flexible, so you are less likely to break a connection, and there is greater flexibility in routing. A last note on the wiring, it is very helpful to "color code" your wiring in a way that is easy for you to track ( left figure above). For example, I like to keep my red and black wiring for my positive and negative voltages (respectively), I often use gray or orange for my common ground, blue for input signal, and white or yellow for internal junctions. If you have several power sources, as well as inputs from a signal generator, it is helpful to make tags for your wires and label them to ensure proper connection later.
When it comes to following a schematic diagram, things are much easier if you layout your components on the board as nearly as possible to the layout in the schematic. In this way, you can see your component values at a glance, as well as making it easier to trace signal routes / troubleshoot failures. The labs at most schools will often instruct you to take a voltage or current measurement at a specific point in the circuit; in these instances having your circuit physically reflect the schematic is a HUGE help! Lastly, as you get into more complex and advanced circuits, it is important to keep more sensitive components (such as Integrated Circuits) away from inductors, relays, and other components where they could be damaged from the magnetic fields.
If the circuit you are building has one (or more) integrated circuits, the number of components and leads needed to build the circuit can get pretty messy fast. To help reduce clutter and make things easier on yourself, it is often useful to place the integrated circuit away from everything else on the board, and place the other components with leads to the IC pins. in this way, it is much easier to decipher things later. If the circuit is to be built into permanent form later, you can consolidate everything to fit into a smaller space.
Step 4: Basic Troubleshooting
All is well - until it's not!
So you have done your homework, you understand your components, and the circuit is built exactly as the instructions show. Flip the power switch... and...NOTHING! It is not uncommon to build a small circuit and discover afterwards that something is amiss. This is all part of the learning process. Knowing where to start with troubleshooting can reduce the hassle and irritation of problems.
Power source: It is generally best to begin troubleshooting with ensuring power is getting to the circuit. If the circuit is operated with a battery, use a multi-meter to check the voltage and ensure their is enough "juice" to power the circuit. If a power supply is being used, there are many factors to consider:
- Power supply mode: Many power supplies have capability to supply constant current (cc) or constant voltage (cv). It is important to ensure that the proper setting is selected in order for proper operation. Most small projects will be connected to a power supply in constant voltage mode.
- Ground / Negative voltage: If your project is powered by a battery, this is not likely to be an issue. When using a power supply, often circuits will have a negative voltage applied (such as to an operational amplifier) as well as having a common ground. It is important to understand the distinction here, and NOT view that negative voltage and common ground as interchangeable.
- Power supply settings: If negative voltage is applied, ensure you know how to adjust power supply settings. This will vary between manufactures, but normally will be accomplished through the selection switches on the front of the unit. The first time I used a power supply to supply -12 volts to an operational amplifier, I failed to check that the settings for voltage had been adjusted for both the + and the - supply. As a consequence, I spent over an hour rebuilding / double-checking my circuit.
Perform a comparison of the schematic and the circuit, if you have built your circuit to mirror the schematic in layout, this step is much simpler.
- Check the orientation of the polar components (diodes, capacitors, transistors).
- Ensure that the leads of the components are not touching creating short-circuit conditions.
- Verify terminal strips, ensure that all component leads and wires are firmly inserted into the contact point and that all components which are supposed to form a junction actually do so. It is easy to accidentally move to another terminal strip when things get cluttered. This creates a break (or open circuit).
- If everything looks good with power, component orientation, and wiring, begin to suspect a faulty component. If the circuit contains an IC, sometimes just swapping that out can solve the problem. Additionally, if you are in a lab environment and recycling components, you may find that you have a faulty capacitor, diode, or transistor that a group has previously wired wrong and destroyed.
The above steps should resolve many of the problems encountered in basic circuit-building, but if everything looks good and it is still not working, it may be time to break everything down, double-check all resistor values, and check all components which are able to be tested with the available equipment. Most schematic diagrams - especially those used for labs in the academic environment- have been built and proven multiple times, so it is very unlikely the issue lies in schematic design. If, however, you are prototyping your own circuit, and are unable to resolve issues through trouble-shooting, it may be most beneficial to go back to the drawing-board and analyze your circuit model for flaws.
Step 5: Don't Give Up
It is very easy to get frustrated when building small circuits. There are literally countless variations of how things can potentially go wrong. Some issues are much more difficult to troubleshoot than others. Although easier said than accomplished, do not let the frustration cloud judgement. Take a step back, cool-down, and evaluate the situation from a logical perspective. I have nearly walked out of labs on multiple occasions due to frustration, only to find that one lead was disconnected somewhere, or a signal output had not been turned on. More often than not, the issue in a circuit is just a small detail. Taking logical and methodical steps to assess the circuit and identify the problem generally leads to a resolution. There are so many facets of electronics to explore, don't let setbacks or failures allow you to give up on this rewarding endeavor!