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Texas Instruments TI-85 ViewScreen™

Date of introduction:  1990 Display technology:  LCD dot matrix
New price:   Display size:  8 * 21 characters
Size:  6.5" x 4.8" x 0.85"
 166 x 121 x 22 mm3
   
Weight:  6.0 ounces, 170 grams Serial No:  032198
Batteries:   Date of manufacture:  mth 02 year 1992
AC-Adapter:    Origin of manufacture:  USA (LTA)
Precision:    Integrated circuits:  2*Toshiba T7778A, T7900
Memories:      
Program steps:    Courtesy of:  Joerg Woerner

TI-81VSC_1.jpg (249465 Byte)The TI-85 ViewScreen panel is connected with a flat-ribbon cable permanently to a modified TI-85 graphing calculator. Placing the panel on a raised platform with an additional lens on the overhead projector enlarges the image of the handheld screen so that each student can follow along. The used platform was in the 90s commercially available from the Polaroid Corporation to project Polaroid color-graph type 691 overhead transparencies.

Dismantling an early TI-81 ViewScreen manufactured end of 1990 reveals no surprises. The reflective background surface was removed from a standard TI-81 graphic LCD display to achieve a transmissive characteristic. The remaining circuit looks really straightforward and consists of two Toshiba T7778A column drivers and one T7900 row driver.

Don't miss the similiar TI-81 ViewScreen connected to the first generation TI-81 VSC. Main differences are the resolution of the LCD display and the added connector for an external AC adapter.

 

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If you have additions to the above article please email: joerg@datamath.org.

© Joerg Woerner, February 23, 2009. No reprints without written permission.