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Electronics Lab

Electronics lab involves the building of prototype circuits and the use of electronics test equipment. Even though a circuit may appear to work on paper, and maybe even in a circuit simulator, it's always important to test it in the real world. In the real world, things like temperature, humidity, static electricity, power supply variations, parasitic capacitance and inductance may affect a circuits operation. These things are difficult to account for in a paper design or even a circuit simulation.

Prototype circuits are usually first built on a solderless breadboard. A solderless breadboard is a small flat white plastic board with rows and columns of holes. The holes in each row are electrically connected together. Holes in different rows are electrically isolated from one another. One of the first things you need to do is verify the continuity of the power buses on your breadboard.

The picture above shows several important electronic principles. Here, a digital multimeter is used to test the continuity of a jumper with minigrabbers on each end. Theoretically the meter should read 0.0, but instead it reads 3.4 ohms. Let's assume 3.4 ohms is close enough to zero.

The first lesson is that what's on one end of a wire will be (or should be) on the other end of that wire. That's what continuity is all about. This lesson will help you throughout your electronics career. If you have a signal on one end of a conductive path, such as a wire or a copper trace, and that same signal is not on the other end, that indicates a problem. That indicates that the conductor does not have continuity.

Another lesson is that any type of connection or interface between one conductor and another conductor always presents some resistance. In this case we have two connections at the interface to the meter, and two connections between the test leads and the jumper with minigrabbers. These contacts should present very low levels of resistance, but in a high speed circuit, like an Ethernet cable, these small levels of resistance will cause signal reflections.

A solderless breadboard consists of groups of holes arranged in 5 holes per group. Below the surface of the breadboard the 5 holes are connected together with a metal strip. With this arrangement, you can plug a DIP circuit package over the breadboard center channel, and use jumper wires to connect between it's pins and other components.

A solderless breadboard has rows of holes on each side that run from the top to the bottom of the breadboard. These are power and ground buses. Some breadboards break these rows in the middle of the breadboard. So you're wondering why your circuit don't work, not knowing that a power or ground bus does not have continuity. So when using a breadboard for the first time, it is important to use a continuity checker (Ohms) to see how your particular breadboard is connected.

In the picture above, a jumper wire is connected at each end of a power bus, and these jumper wires are connected to multimeter probes using jumper wires with minigrabbers at each end. The multimeter is set to the ohms scale and the meter reads 1 ohm, indicating that the bus has continuity all the way across.

The above picture shows the same setup, except the jumper wires are connected at each end to different power buses. This time the meter is displaying a vertical line on the left side of of its display, indicating no continuity, in other words, the different power buses are not shorted together.

The picture above shows a 14-pin DIP (Dual In-line Package) integrated circuit plugged into a solderless breadboard. The pins of the integrated circuit are connected to components on the breadboard using 24 guage jumper wires. Some people, when they create breadboard circuits square the wires off neatly. This is helpful if you are creating a large prototype circuit.

You can build and experiment with electronic circuits using the method described above. The materials and components required can be obtained at amazon.com or digikey.com.


Learn more at amazon.com

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