Assistive Communication Device

Designers: Daniel McCormick
Client Coordinators:
Supervising Professor: Dr. Larry N. Bohs

A supplementary communication device was designed for the client, a 6-year old boy who has limited control over his body from the neck down and cannot use speech to communicate with others. Currently he uses a Dyna-Vox to communicate but it does not provide an adequate level of self s ufficiency in many situations. The new device allows the client to communicate “yes”, “no” and simple phrases using a single switch.

How this project helped
The client’s assistive communication device provides an effective and reliable means of basic communication. The client is able to readily answer simple yes and no questions as well as signal for attention both at home and at school. In addition, the client can communicate six custom messages. The radio frequency connection between the main unit and the output unit allows the client to communicate a request form a distance. For example, it is now possible for the client to call to his mother from his bedroom if  his mother is in the kitchen.

Most importantly this device allows the client to be more independent; he does not require assistance once the device has been connected and activated. This allows the client to use the device in a variety of situations.

The device consists of three sections: the main unit, the selection unit, and the output unit. The device can be set to three different modes: 1) School, 2) Home, and 3) Switcher.

In all modes, the device scans through all possible options; when the desired message is reached, the client activates the message using a single switch.

The selection unit provides cues to the client through LED arrays or a LCD display. The LCD displays 2 rows of 16 standard ASCII characters or custom characters. A small slide switch allows the backlight to be activated, or turned off to conserve power. In addition, if a selection is not made within a minute the unit goes into sleep mode to conserve power.

In the School mode, the client selects “yes”, “no”, “attention” or “urgent attention”, which lights a corresponding LED on the remote output module. The Home mode is identical to the School mode except that audio is added to the output. The Switcher mode has the four standard messages but also six additional custom digitized voice messages, each of which can be up to 18 seconds in duration.

The front panel of the main unit contains controls for mode selection and volume, the power switch, the audio speaker and the microphone.A 8 pin DIN connector on the main unit provides power and control for the selection unit, which contains a row of LED’s (for “yes”, “no” and “attention”) as well as an LCD display (for selecting audio messages). A 1/8″ switch jack is located above the DIN connector. On the lower left side is a 9 volt output that provides an alternative power source for the output module. A male 9 pin D serial connector is provided on the upper left of the device so a serial cable can be attached for reprogramming. The voltage supply is  conditioned by a low quiescent current voltage regulator.

A Basic Stamp II microprocessor monitors the state of the input buttons and controls operation of the device. The radio frequency communication between the main unit and the output unit comprises a Holtek encoder and decoder (HT-6104 and HT-6034) and a Linx transmitter and receiver (TXM-315LC and RXM-315LC). An ISD33120 chip is used for record and playback of messages.

The audio output level is adjusted using a log-scale potentiometer on the front of the device. The output unit is powered by a 9V battery, but it can also be powered from a wall transformer to conserve battery power. There are three different programs associated with the ACD. The first two are written in P-BASIC. The first is the normal run program. The second allows the user to records messages and listen to them. The third program is written in C and runs on a normal PC. This program is  used to interface with the ACD through its serial connection.

The cost of the device is approximately $600.

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