Thermo-sensor Lab

Purpose: to amplify a thermo-sensor to a specific output range.

Preperation

     Given:

• A LM35 that produces 10 mV/°C.
• work between 15 °C to 35 °C.

Using a difference amplifier, we shifted the range produced from 150 mV - 350 mV to

0V - 5V.

 V_1 = 150 mV, V_2 is the range given by the LM35
 Our gain is a factor of 25 so, R_f = 150 kΩ and R_i = 6 kΩ.

Experiment

We built the following circuit:

V_1 was measured at the left potentiometer while V_2 was measured at the one on the right

We made

V_2 = 350 mV to verify it was working.

 V_out was measured to be 5.05 V

Conclusion

We amplified 350 mV into 5V by using a power supply and voltage dividers to represent the LM35 at 35 degree C. The lab was a success.

MatLab and Complex Numbers

Purpose: To understand how to work with complex numbers in MatLab.

Tutorial:

1) Example with simple functions

1. 
   
2. 
   

2) Finding Magnitude and Phase angle

Assignment 1)

Assignment 2)

Assignment 3)

Assignment 4)

Conclusion:  Matlab provides a quick and easy way to work with imaginary numbers and solve linear systems of equations.

MOSFET Control of an Electric Motor

Purpose: To control the speed of the motor with a MOSFET circuit.

Experiment: We set up the following circuit:

Varying the resistance on the POT varied the speed of the motor. Going below 3.9V made the motor stop.

The POT was replaced with a function generator producing square waves at 10kHz with duality on and the oscilloscope to see the motor voltage.

When the frequency was reduced to only a few hertz, depending on the voltage the motor turned on and off.

Conclusion: Changing the speed on the motor was as simple as varying the voltage on the motor. This could be done with a varying voltage supply (function generator) or varying resistance (POT). The function generator worked much better than the POT.

Second Order Circuit Problem Example

Purpose: To go through various steps to understand how to do a second order circuit problem.

Introduction: We went through the "Second Order Systems" example at http://www.mhhe.com/engcs/alexander2e/netan_tutorials/tutorials/tutmenu.htm

Example:

These problems are not so bad when you take it one step at a time.