Experiment 4 - Prelab
In lab 2 we discovered that resistors, motors, and incandescent bulbs all have I-V graphs which can be
characterized by sloped lines which characterize the resistive behavior, outside of some transition
regions and "warming up" areas. The voltage is directly related to the current. However, in order to
control the ECE cars, we need our circuits to be able to encode logic. The circuits need to be able to
represent the concepts of "true" and "false", "on" and "off" and be able to perform basic Boolean
operations using these concepts. This is highly nonlinear behavior – behavior that is exhibited by the
simplest device that we have worked with, a switch. Like the one on the back of your vehicle or the
one in the test box.
To appreciate the complexity of this simple device – a switch, try and draw an I-V curve for a manual
switch. Conceptually, this would be the perfect device to implement the two-state logic that you have
learned about in lecture and that you will be using to implement the circuitry on your vehicles. A
manual switch has an obvious drawbacks for all applications where speed, size, complexity, and
autonomy are desired. An electronic device that can behave as a switch, a switch that is small, fast,
and can be controlled electronically. These electronic switches will be used to implement the two-state
Boolean arithmetic that all of our digital devices use to operate.
The beauty of a two-state system is that the simple concept of "on" and "off" can be mapped onto the
two states sometimes called "true" and "false" (if we are speaking in terms of logic) or "1" and "0" (if we
are speaking in terms of Boolean logic).
1. Propose a method of encoding the concepts of "true" and "false" in an electrical circuit.
You can explain in general terms such how currents flow or how voltage changes
without necessarily assuming that it can realistically be built by existing eletronics.
Play "what if..." Be sure to explain how the concept of 'true' and 'false' are
differentiated in your method.
2. Would it be difficult to implement your method using linear devices (such as
resistors)? Why or why not?
