MEMORANDUM

FROM: EECE 380 Lab Group L2B5

TO: Dr. Michelson and Lab TAs

DATE: March 30, 2014

SUBJECT: Spectrum Analyzer Fourth Weekly Memo

We mainly focused on four components for spectrum analyzer project this week, peak detector, crystal ladder, amplifier, and LabVIEW. The first three parts are completed, and the software part is halfway finished.

The peak detector is used for detecting signal level peaks. The peak detector provided a DC output from the AC input of the resolution filter. Our group decided to use simple peak detector rather than precision one, because the high frequency op amp is unstable at 8MHz. A simple peak detector’s output is similar to a precision one, and it can work very well even at high frequency. The wire connection of a simple peak detector is simple. After calculating the values of the resistor and the capacitor, connect them in parallel, and then connect with a diode.

The next component is Crystal Ladder Resolution Band Pass Filter. The crystal ladder filter utilises Quartz crystal oscillators that have a resonant frequency of 8MHz. This allows us to build a band pass filter around the center frequency of 8MHz. The two crystals provided extra attenuation for the stop band and the capacitors improved the high frequency roll-off by adding extra poles. The band pass filter was tested by using tracking generator test set. Our group used online crystal ladder calculator to figure out the values of the capacitors and resistors, and then wired then up on the breadboard.

For the amplifier part, we used two LM6181 chips to build. We also chose the tantalum capacitors because these capacitors have high capacitance per volume and weight, lower equivalent series resistance, lower leakage, and higher operating temperature than other capacitors. Because we want the amplifier to have a better performance, the unique features of tantalum capacitors make them perfect for the project. The next step is to connect them on the breadboard based on the schematics we already designed.

The last task of this week is the LabVIEW programming. We have mapped out the entire program and are currently able to generate a  sawtooth waveform output from myDAQ to the circuit. We are also able to display input voltages and frequencies using the waveform and x-y graph functions in labVIEW. The main tasks left for completion are minor tweaks such as the conversion of the sawtooth waveform from voltage to frequency within labVIEW.

Sincerely,

EECE 380 L2B5

FROM: EECE 380 Lab Group L2B5

TO: Dr. Michelson and Lab TAs

DATE: February 24, 2014

SUBJECT: Fifth Week

Summary In this week, our team has reached the final stage of our project. We calibrated the water level sensor, modifies the code, soldered the circuit, and installed the actuators. For the water level sensor, we poured the water into the cup and recorded the corresponding voltage, then we plotted the graph on Excel. We also had the line of best fit and the equation for the graph. Water level sensor acts as a capacitor, it connects to LM555 timer, which generates frequency. The timer then gives the signal to LM331, which converts the frequency to voltage. Finally, the voltage goes through LM358 op amp and sends the signal to the modem; the modem will then send the email to our gmail account. The other sensor for this project is temperature sensor, we soldered the entire circuit on a single solder board. For the actuators, we use LEDs and buzzer. We have six LEDs to tell us about the water level, and the buzzer buzzes when the water level goes above the threshold. For the temperature sensor, we set 20 degree Celsius as our threshold point, when the temperature goes above 20 degree, the green LED is turned on; when the temperature drops below 20, the yellow LED is turned on.

Sincerely, EECE 380 L2B5