ELEC 243 Lab

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There are several aspects to this organization ranging from small details to the big picture.

Color Coding

Your wire kit contains an assortment of different colored wires. You could just pick pieces of wire at random, or you could try to use the different colors to designate different signals. There aren't enough colors for each signal to have its own, but you can use different colors to denote different classes of signals.

One set of signals you should color code are power and ground. In particular, you should have a different color for +15 V, -15 V, and ground and you should not use any of these colors for other signals. It would be nice to use "standard" colors for these, but unfortunately there are several competing standards. One color that nearly everyone agrees on is that red should be the positive power supply voltage. Most automotive and electronic wiring uses black to denote ground. Electronic wiring which uses black for ground often uses blue for the negative supply. However, our power supply and breadboard use green to denote ground (the convention used in house wiring) and use black to denote the negative supply.

So we have two possible "standard" color codes for power: (1) red = +Vcc, green = gnd, black = -Vcc, and (2) red = +Vcc, black = gnd, blue  = -Vcc. You could use either of these, or make up your own. The pictures in this lab use set (1).

Another useful thing to color code would be the wires or "probes" from the interface board connector. That way you can tell which wire is CH1 of the scope or which is the function generator output without having to trace from one end of the wire to the other.

Power Busing

Op amps require external power in order to operate. Since we will be using several op amps in this and subsequent labs, and each op amp requires several power connetions, we need an efficient and uncluttered way of distributing the power supply voltages.

If we plug an op-amp in with pin 1 in the lower left corner, then the writing on the package and pins 1 through 4 read left to right. In this case, the positive supply pin is on top and the negative supply on the bottom. To simplify power wiring, we can run positive, negative, and ground on each of the triple bus strips. Doing this and running ground on the remaining buses gives us the following layout for power:

Interface Module Connector Assignments

Some of the connectors on the Interface Modules are dedicated to a single function (e.g. the telephone handset or the sound card). Others (e.g. the BNC and phone jacks) are more flexible and may be connected to a variety of signal sources or destinations. It will be helpful to establish standard assignments for these connectors as well.

In the instructions and photographs, we will be using the following assignment: