Last edited 30 August 2014 by Tom Igoe
The easiest way to get started building electronic circuits 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 the right 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. This lab shows how to set up a breadboard with an independent power supply (8-12V) through a 5V Voltage Regulator (7805).
To get the most out of this lab, you should be familiar with the following concepts beforehand. If you’re not, review the links below:
Safety Warning: When inserting components on or removing components from a breadboard always unplug power supply first!
|Solderless Breadboard||22-AWG hook-up wire||Voltage regulator||Soldered DC Power Jack||Wire strippers||Multimeter|
This picture above shows a typical breadboard with a 7805 5-Volt voltage regulator mounted on it. 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, others have multiple side rows, and some have no side rows at all.
On each side of the board are two long rows of holes, with a black or a red line next to each row (on many boards, you’ll see a blue row instead of black). 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.
The image below 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 detailed photo below illustrates how the holes and strips are related.
The reason for the center divider is so that you can mount integrated circuit chips, like a microprocessor, on the breadboard. IC chips in a DIP package (Dual In-line Package) 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.
The regulator in the picture above is there to supply 5 Volts to the two red side rows. The two black side rows are connected to ground. These will be your power and ground bus rows. They give you lots of convenient places to connect to power or ground as needed. The red and black wires (red for power, black for ground) connect the bus rows to the rows where the regulator’s ground and output pins are plugged in. The image above shows a closeup on the connections to the regulator pins’ rows.
With your board connected like this, you’ll be able to build many different 5-Volt circuits on the board. The last thing you need to add is a power connector to connect 8 – 12 volts DC to supply power for the voltage regulator. The image below shows a power connector connected to the input and ground pins of the voltage regulator. Related Video: Wiring a power supply using a DC power jack
The photos below show an LED and a resistor connected in a breadboard. Some are connected correctly and others are not. Take a guess as to whether the LED will light or not, then roll your cursor over the image to find out. For more details, click the link below the image. All of the circuits below should realize the same circuit, shown below:
If you connected an LED and resistor just like this, and it didn’t light, check to make sure that the anode (the long leg) of the LED is connected to the resistor, and the cathode (the short leg) is connected to the ground wire.
Below, 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.