The Audible Counter

Designers: Luke Palmer, Jeffrey Earhart
Client Coordinators: Antonia Pedroza, Judy Stroupe
Supervising Professor: Dr. Larry N. Bohs

Orange Enterprises (OE, Hillsborough, NC) provides employment to people with a variety of disabilities, including cerebral palsy, mental retardation, and those with visual and/or mobility impairments.  The employees are paid to complete basic tasks that often involve counting an assigned number of objects for placement in supply kits or papers for work-packets.  The counters used currently at OE are small, and difficult to increment and reset; therefore, they are not suitable for many employees. The goal of this project was to design a counter that could receive input from a variety of external switching devices and output the count with both a large visual display and spoken numbers.  Specific objectives were that it be usable by employees with a variety of disabilities, adaptable to needs of new employees, easy to use, portable, unobtrusive, rechargeable, and able to accept a wide range of input devices. A base unit was designed with multiple input ports to which either a commercial switch or two custom-designed motion-sensing switches could be connected.  Audio and visual outputs of the count are available, and the design allows for simple addition of other input devices.

How this project helped
Workers at OE are paid by the amount of work they get accomplished, rather than the amount of time they are on the job.  Employees often say that they do not earn as much money as they would like.  The audible counter allows some employees to do jobs not previously possible, and helps others improve their efficiency, thereby allowing them to earn more. After 2 months of use, Antonia Pedroza, assistant director at OE, commented,  “The audible counter was brilliant and the students exceeded my expectations for that counter. The consumers enjoy the continuous feedback it provides and it therefore works as an incentive to stay on task for longer periods of time”. Judy Stroupe, one of the supervisors at OE, added “The audible counter has allowed several of our employees to become independent in work in which they previously dependent on their supervisor.

The audible counter, shown in Figure 1, consists the counter unit, three interchangeable inputs (a foot pedal, an ultrasonic motion sensor, and a passive infrared sensor), and a Plexiglas storage container that doubles as a stand for the counter unit.

The device is powered by six internal AA NiMH batteries, which require a specialized charging circuit that monitors both the voltage and temperature of the batteries during each charge cycle.  These batteries will power the device for approximately one work week under moderate use, and can be recharged in 2-3 hours.  A high-efficiency switching regulator delivers power to the audio amplifier and also the PIC microcontroller, which controls the overall system.

The foot-pedal, visible at the bottom of Figure 1, is made of a metallic case with a textured, rubber top. This commercial pedal is normally used with an electronic keyboard, and it connects to the counter unit with a _” plug. The custom-built ultrasound motion sensor (stored in the container at the top left of Figure 1) is a black rectangular box with two metallic cylinders coming out of the front: one is the transmitter and the other is the receiver. Passing a hand or other object in front of these transducers triggers an increment signal.  This device terminates in a four-pin plug.  The passive infrared device (stored in the upper right of Figure 1) is a small black box with a plastic dome centered on the top face.  Passing a hand in front of this device also increments the count; it uses the same connector as the ultrasound sensor.

A double-sided printed circuit board, fabricated using iron-on methods, contains the electronic circuit.  This board minimizes total size, provides good product durability, and accommodates the two surface mount IC’s used in the device.

The front of the device (Figure 1) contains two LCD displays.  The smaller display, showing “07”, indicates the goal count for a worker to reach before starting a new batch.  This display, 1.5” tall, helps those employees who do not understand the concept of numbers to detect their completion of a task by matching the current count display to the static goal display.  The larger display (“03”) is the current count, displayed in large 4” LCD’s.  Beneath the smaller display is the speaker, which voices the current count upon each increment.

The audio output uses an ISD voice record/playback chip with on-board memory, in which computer-generated sampled numbers are stored.  A differential audio amplifier, chosen due to its efficiency and high output power for low supply voltages, drives the speaker.  The audible counter also has a volume control and an automatically switching headphone output.

The cost of parts for the audible counter was $193.

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