Class: BE209
Group: R4
Members: BANIEWICZ, LEAH K; BAO, BRIAN A; DONTHAMSETTY, RAMESH C; KAUER, LAURA M; MILLS, JUSTIN R; SHEIKH, LAMIYA A

Date: December, 2002

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Introduction
Visually impaired individuals must rely on senses other than sight for distance perception.  The cane, an extension of the sense of touch, conveys the immediate surface landscape; however, it does not provide any information beyond its immediate length. Our device is an attempt to provide a means for the blind to create a clearer “picture” of their surrounding environment by perceiving the distance of objects through varying audible tones. This variance, in the form of pitch change, will transform object distances into distinct sounds that a person can recognize.

The device utilizes the intensity of light reflected off the surface of an object detected by a photoresistor, which changes its resistance based on the light received. If an object is moved closer to the photoresistor, the intensity of reflected light will decrease, and therefore the resistance of the photoresistor will increase. The 555 timer chip produces a pulse in the circuit that depends on resistances (R1, R2, the photoresistor) and capacitance (C). Only the photoresistor is variable, and the change in resistance produces a variable pitch. The current is passed through a capacitor and is converted to a perceivable audio signal through an 8? speaker. We tested the effects of varying values of capacitance and resistance on the time constant of the circuit, thereby calibrating a range of frequencies that are not only audible to the human ear but also varying enough to accurately inform the blind.

Our hypotheses and tests include: 1) the Inverse Square Hypothesis, the voltage drop over the photoresistor is linearly related to the intensity of the light; 2) the Linearity Hypothesis, there is a linear relationship between frequency and voltage drop; 3) the Color Hypothesis, the device registers distinct frequencies for obstructions of varying colors at a common distance; 4) the Sensitivity Hypothesis, the device will be most sensitive to the proximity of dark objects as opposed to light objects; 5) the Detection Test, the distance at which the circuit recognizes an obstacle is dependent on its color characteristics; 6) the Reset Test, a reset mechanism (Pin 4) that shorts the circuit if the intensity of light on the photoresistor is high (due to a bright room or strong sunlight) requires a manual change of a potentiometer for proper performance. The first hypothesis, the Inverse Square Hypothesis, confirms the consistency of the device in terms of distance away from the photoresistor of a common object. It is important to verify this linear relationship between voltage and light intensity to ensure accuracy of recorded measurements. If a linear relationship is not found, another correlation must be addressed to allow for accuracy. Our second hypothesis, the Linearity Hypothesis, tests for consistent proportionality between the change in voltage recorded and the frequency of beeps; this will test the precision of the device. The objective of hypothesis three, the Color Hypothesis, is to observe the reaction of the device to objects of different color when placed at a fixed distance of 5 cm, thereby offering comparisons between colored objects. Hypothesis four, the Sensitivity Hypothesis, tests the sensitivity of the device with three representative colors to determine with which colored objects the device will perform best and its effectiveness with all varieties of obstructions. The fifth experiment, the Detection Test, is important in application to determine the practical distance at which the device will first detect an obstacle. This test extends the previous experiments to more practical terms. In the Reset Test, the reset mechanism acts as a powerful tool in silencing the device when light intensity exceeds a threshold value due to the absence of nearby objects. This Reset Test determined possible resistor values needed to achieve the threshold for various environments.

Our ultimate objective was to construct a portable distance-sensing device for the visually impaired. In our case, the device would allow a blindfolded individual to navigate through a simple maze constructed in the Bioengineering Laboratory without incident or contact with obstructions. The performance in a “labyrinth” confirms the practicality of the device in real-world situations.