Download Memorandum DATE: 26 September 2015 TO: Professor Timothy F

Memorandum
DATE: 26 September 2015
TO: Professor Timothy F. Wheeler
FROM: Nasser Aljadeed
SUBJECT: EE300W Lab 2 Status Report
The main task for Lab 2 is to design an Optical Theremin, a musical instrument
that can be played without physical contact. It functions by using two photodiodes as
light detectors that detect light reaching the circuit, allowing users to control the
frequency pitch and volume that the theremin produces based on light intensity.
During the first week of lab 2, Greg and I designed a circuitry to measure the
leakage current from the photodiode using a TL074 op-amp that functions as a
transimpedance amplifier. The transimpedance amplifier converts the diode current into a
negative signal voltage, whose magnitude will control either the frequency or volume
tone of the theremin.
During the second week of lab 2, our task was to design an auto-tuned optical
theremin. Before approaching this task, we started the LabView code to process the
detector’s signal for controlling the frequency and amplitude of the theremin. We
acquired the outputs of both detector circuit’s signals with the DAQ assistant and set up
the DAQ assistant to receive signals presented to the myDAQ’s analog input ports (ai0,
ai1). We still have to design two VI blocks, one for the frequency and the other fore
amplitude. By using equations: "(sin - Lmin Lmax-Lmin)(f – f ) + f ” and “(sin max
min
min
Lmin Lmax-Lmin)" for the frequency and amplitude VI, respectively, we are able to
normalize the input to set the max and min light levels for the light detector and coerce
the signal to remain within the range of normalized values.
Before lab 2 next week, Greg and I will meet to work on the rest of the LabVIEW
code, including finishing off the frequency VI and amplitude VI using both equations
above. We will then add an auto-tune feature to our theremin design that tunes the pitch
to tones in the equal-tempered scale within the human hearing range.