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---- PROTOTYPE --------- PURPOSE: To design a sensory aid (vest) to provide musical and tactile stimulation for a child with cerebral palsy and blindness. The child is nonverbal and therefore cannot effectively communicate the need for stimulation. The Sensory Vest is a battery-operated sensory stimulating system that can be worn by the user and is self-contained. The user is able to control the various stimuli. The inside and outside layers of the vest are made of a durable lightweight denim. These layers encase up to one inch of easily compressible foam.
Embedded in the foam are the circuit components, wiring, switches, and speakers. Three buckle closures are attached to the backside of the vest for easy donning and doffing as well as maintaining adjustability. Because the vest is intended for a young child, it measures only 16 inches wide by 17 inches tall. Lying flat, the thickness of the vest measures 1.5 inches. The arm-hole circumference is 16 inches. The opening for the neck and head has a 25 inch circumference.
Raised rigid musical notes adorn each shoulder. The center of the chest holds a large circular foamy texture and is flanked on either side by two strips of Velcro. The Velcro strips allow for the interchanging of four different textures: 1) bumpy, 2) soft and fuzzy, 3) beaded, and 4) hanging pom-poms. An oversized pocket near the bottom of the vest is lined with thick fur. At any time, the client can access any of the different textures. The interchangeable patches can be changed by a supervisor. To hear music the client presses the switch located under the raised rigid musical note on the right shoulder. A 15 to 30 second children’s melody plays after the button is pressed. The speakers for the sound element are located just above the music notes on each shoulder. If the switch is pressed a second time, while the first tune is playing the circuit will automatically switch to the next song on its play list. A total of 12 songs will cycle through after each pressing of the switch. The motor generating the vibration is housed in the chest region of the vest, directly beneath the soft foam circle. To activate this stimulator, the user must press the switch located at the bottom of the foam circle. The control circuit is designed to create pulsing vibrations for each press of the switch. Each pulse is around 2.5 seconds followed by 2.5 seconds of no vibration. This process repeats four times before stopping. One circuit used in the design is a 12-tone melody generator circuit. The output of the circuit required an impedance of 8 ohms, which was satisfied by using two 16 ohm speakers wired in parallel. A potentiometer incorporated into the circuit regulates the current flow through the speakers to control the volume. Two AA batteries produce the voltage and current necessary for operation. Because of their long life and cost effectiveness rechargeable batteries were selected. Two rechargeable AA batteries, wired in series, provide 2.8 volts and have a current capacity of 1800 milliamp hours.
A second circuit was designed to create a sequence for the vibration. This circuit is composed of a bistable 555 timer, a 555 clock timer and a 4017 decade counter as well as other basic circuit elements. The output from the 4017 controls a relay that operates a small DC motor spinning an unbalanced weight. This circuit is controlled by a lever switch and nine volt battery. The clock pulse drives the 4017 decade counter. Every other output of the decade counter is connected through a diode to a transistor-controlled relay. Once the relay is turned on, 2.8 volts is sent to the motor, producing vibration. The total cost of parts and labor was $660. TITLE: Sensory Vest. JOURNAL: NSF 2006 Engineering Senior Design Projects to Aid Persons with Disabilities. REF: Chapter 20: pp. 370-371. PAGES: 3 with cover. 2006.
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