Electronics S. O'Toole THE LABORATORY REPORT It is imperative that proper records be kept whenever scientific investigation is conducted. In your classes the laboratory report serves this purpose, in industry an engineering notebook is used. Laboratory documentation serves many purposes: They reenforce the concepts that are learned in an orderly manner. They provide a means for others to evaluate your work. They maintain research data as a permanent record. They provide a reference resource for future study. They provide a means of continuous monitoring of a project. They are suitable for patent defense and other legal actions. Each new concept investigated will be documented in formal laboratory form consisting of an Introduction, Body, and Analysis section. Introduction The introduction states the objective(s) of the investigation and the means by which the experiment will be conducted. Body The body develops the necessary details that lead to the final results. The body will include: The proposed circuit and/or initial software code. The required parameters and new concepts defined. Each design calculation with reference. Equipment and parts used in the investigating. Measurement results with test procedure used. Modification to initial circuit and/or code. Final circuit and/code with measurement results. Analysis The analysis section uses the procedures and results from the body of the report to prove the objective(s) set forth in the introduction. Below is one segment of an lab exercise. On the next page is an example of the laboratory report related to the lab exercise. COMPUTER ELECTRONICS FUNDAMENTALS LAB Modern personal computers use massive numbers of transistors acting as switches is digital circuits. The main advantage of digital circuits over analog circuits is their ability to reject electrical noise. This lab will investigate a simple digital switch circuit called a BUFFER and its ability to reject simulated noise applied to its input. 1. build the simple CMOS switch shown at the right. Hook the input to a variable supply. 2. Apply various voltages between 0 & +1 volts to the input and record the LED state. 3. Apply various voltages between +4 & +5 volts to the input and record the LED state. 4. Raise the input from 0 toward +5 slowly and record the voltage when the LED just turns on. 5. Summarize your findings from steps 1-4 above. CIE25 LAB1 Mr. Short A. Circuit 2-30-00 DIGITAL NOISE REJECTION Introduction The main objective of this laboratory is to investigate a digital circuit's ability to reject electrical noise. In digital there are only two valid states for an input or output. One state is referred to as a LOW or Logic Level "0" and is a voltage near zero. The other state is referred to as a HIGH or Logic Level "1" and is a voltage near the power supply potential. Unwanted voltage variations called NOISE are present in all electronic circuits. Noise will cause the input of a digital circuit to vary slightly above and below the ideal values specified for a 0 and 1. Digital circuits are designed to reject this variance so long as these voltage variations do not become excessive. Body The below circuit was built on the trainer protoboard as per step 1 of the lab. This was challenging because each component had to be identified and placed properly with its interconnecting wires. The trainer's +5v supply was used to power the circuit, and a separate laboratory supply was used for the variable input voltage. The digital part is called a buffer. In a buffer the output logic level follows the input logic level ( 0 in = 0 out and 1 in = 1 out). The input voltage condition will be set with the laboratory supply and the output state will be monitored with the LED such that logic 0 = LED off & logic 1 = LED on. The circuit was powered and voltages between 0 and +1 volt were applied to the input as per step 2. The LED always remained off. Voltages between +4 and +5 volts were applied to the input as per step 3. The LED always remained on. The voltage was slowly raised from 0 to +5 volts as per step 4. It was observed the LED turned on at about 2.65 volts. Analysis The advantage of a digital circuit like a computer over a analog circuit like a radio is its ability to reject ever present electrical noise. The ideal LOW or logic level "0" for a digital circuit would be 0 volts. In step 2 of the lab the input was varied from the ideal 0 volts to +1 volt to simulate an entire volt of electrical noise above the ideal value. In all cases the output stayed at logical level "0" or off. The ideal HI or logic level "1" for a digital circuit is the power supply voltage, or +5 volts in this lab. In step 3 the voltage was varied from +4 up to the ideal of +5 volts to simulate an entire volt of electrical noise below the ideal HI value. In all cases the output stayed at logic level "1" or on. The circuit did reject one full volt of simulated noise both for a LOW and HI input condition. Step 4 of the lab showed the actual switch point to be 2.65 volts or about half the supply. The switch point is not normally used in design.