Lab 1 - Introduction to Circuits

Lab Objective
The objective of this lab was for us to:

• Review how to implement simple breadboard circuits
• Review how to read data specifications for components
  
• Design a circuit that turns on an LED under the command of signals by switches and logic chips
• Learn how to use an oscilloscope and calibrate an oscilloscope probe
• Create TTL signals with an LM555 timer chip and various logic chips
• Use transistors to amplify said TTL signals to drive LEDs, motors, and speakers

Parts
PN2222 NPN transistor; 74LS00, 74LS02, 74LS04, 74LS08 logic gates; power supply; LM78L05 voltage regulator; breadboard; LEDs; switches; LM555 timer chip; potentiometer; pager motor; small speaker

Background
We were given the following circuit diagram on which to base the rest of our design:

Process

• We set up a voltage regulator to supply 5V to logic chips.
• We selected and set up the NAND logic chip. This was based on the fact that we wanted 2 pressed switches (A = "1" and B = "1") to return Q = "0", which would serve as one input into another NAND chip and allow the out put of that to be Q = "1". This would in turn go to the base, and the transistor would be activated, turning on the LED. See below for truth table verification.
  

• We calculated the resistances necessary to light the LED. See below for sample calculations.

• We built the circuit for the LED based on the circuit diagram above with our specified gate and resistors. See below for layout.

• We calculated the resistances necessary to drive the pager motor instead of the LED. See below for sample calculations.

• We built the circuit for the pager motor with our specified resistors. See below for layout.
  

• We familiarized ourselves with the LM555 timer chip to create a 1 Hz square wave and then replaced a switch with said timer chip.
• We calculated the resistances necessary to drive the speaker instead of the pager motor. See below for sample calculations.

• We built the circuit for the speaker with our specified resistors and a potentiometer to regulate frequency.
  

Final Circuit
This is our final circuit with calculations.

As an expressive musical instrument, our circuit (while very rewarding on the educational side of things) was at the very best a noisemaker. It had a limited range of notes because of the fact that it would saturate when current was high.

Human-circuit interface was less than ideal, as we had no ability to vary volume and notes simultaneously (as most instruments minus percussion do). Also, while the system is analogous to a trombone in that there are not any stops marked so that one knows where to adjust to for the next note, it is different from it in that it is very small, therefore requiring more accuracy and precision to get to that next note than a trombone.