1.1: Lab Safety and Tools

If proper procedures are followed, the electrical lab is a perfectly safe place in which to work. There are some basic rules: No food or drink is allowed in lab at any time. Liquids are of particular danger as they are ordinarily conductive. While the circuitry used in lab normally presents no shock hazard, some of the test equipment may have very high internal voltages that could be lethal (in excess of 10,000 volts) along with the 120 VAC power used to operate the equipment that can also be lethal if good safety practices are not followed. Spilling a bottle of water or soda onto such equipment could leave the experimenter in the receiving end of a severe shock. Similarly, items such as books and jackets should not be left on top of the test equipment as it could cause overheating. Use caution in storing these items during lab periods to avoid trip or fall hazards in the lab.

Each lab bench is self contained. All test equipment is arrayed along the top shelf. Built into the bench is a power strip. All test equipment for this bench should be plugged into this strip. None of this equipment should be plugged into any other strip. This strip is controlled by a circuit breaker. In the event of an emergency, all test equipment may be powered off through this one switch. Further, the benches are controlled by dedicated circuit breakers in the main lab panel. Located at the front of the lab is an A/B/C class fire extinguisher suitable for electrical fires. Also at the front of the lab is a safety kit. This contains bandages, cleaning swaps and the like for small cuts and the like. Familiarize yourself with the location of these items in the lab. For serious injury, the Campus Security Office should be contacted.

A lab bench should always be left in a secure mode. This means that the power to each piece of test equipment should be turned off, the bench itself should be turned off, all AC and DC power and signal sources should be turned down to zero, and all other equipment and components properly stowed with lab stools pushed under the bench. Any cables or cords used in the lab should be stored properly after the exercise is completed.

It is important to come prepared to lab. This includes the class text, the lab exercise for that day, class notebook, calculator, and hand tools. The tools include an electronic breadboard, test leads, wirestrippers, and needle nose pliers or hemostats. A small pencil soldering iron may also be useful. A basic DMM (digital multimeter) rounds out the list.

A typical breadboard or protoboard is shown below:

Figure \(\PageIndex{1}\)

This particular unit features two main wiring sections with a common strip section down the center. Boards can be larger or smaller than this and may or may not have the mounting plate as shown. The connections are spaced 0.1 inch apart which is the standard spacing for many semiconductor chips. These are clustered in groups of five common terminals to allow multiple connections. The exception is the common strip which may have dozens of connection points. These are called buses and are designed for power and ground connections. Interconnections are normally made using small diameter solid hookup wire, usually AWG 22 or 24. Larger gauges may damage the board while smaller gauges do not always make good connections and are easy to break.

In the picture below, the color highlighted sections indicate common connection points. Note the long blue section which is a bus. This unit has four discrete buses available. When building circuits on a breadboard, it is important to keep the interconnecting wires short and the layout as neat as possible. This will aid both circuit functioning and ease of troubleshooting.

Figure \(\PageIndex{2}\)