LCD display used in HP calculators
In 1980 Hewlett Packard introduced the new economical LCD display technology for their calculators. See this article published in the HP Journal of March 1980. The rechargeable batteries were replaced by smaller standard batteries or button cells. The smaller batteries and the flatter display made it possible to build smaller calculators. The ongoing evolution of the integration of more functions into one chip fabricated in a CMOS technology decreases even further the power consumption. A good example are the calculators from the Voyager series, that run for many years on three small coin cells.
A other advantage of the LCD technology is the freedom to design model specific displays.
7 Segment displays
The digits of a seven segment display are build from a 8 shape configuration of 7 segments. By activating a subset of these segments the numbers 0 up to 9 can be displayed. This 7 segment display technique is also used for many LED displays.
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The Voyager series uses a simple 10 digit 7 segment display with one line of annunciators below the digits. |
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The low end models of the Pioneer series uses a single line 12 digit, 7 segment display. This display has one line with annunciators below the digits. |
14 Segment displays
By increasing the number of segments from 7 to 14, combinations of segments can also display characters. This type of display is also known as the 'star burst' display and is used in the Coconut series.
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The picture on the left shows the 14 digit star burst display of the Coconut series. It can display text in the Alpha mode. |
Character matrix display
With a character matrix display, a character is composed by a small matrix of pixels. Each character position is build by a separate matrix. The readability of these displays for characters is much better compared to a 14 segment display. The drawback is the more complex driver structure. This required a higher level of integration.
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The mid range models from the Pioneer series uses this type of display. The display shown on the left is the display of the first generation HP-32S calculators. |
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The picture on the left shows the second generation display used in the later version of the HP-32S models and the HP-32SII models. The size of the pixels in the matrix have been enlarged to improve the readability. |
Graphic matrix display
Graphic matrix displays consists of one large matrix of pixels. This enables the possibility to display all kind of characters, graphs and pictures. The size of a character is no longer limited by its own matrix. To control such a display, a more intelligent and powerful display driver and software are needed. These kind of displays are used in the top models of the HP Calculators. Some models from the Pioneer series, the Champion series and the Charlemagne series uses this type of display.
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The high end models of the Pioneer series have an 132 x 16 pixel graphic matrix display. This display can show two lines of characters or one line of characters and one line of soft key labels. The picture on the left shows the first generation display and bezel of the HP-42S. This generation had the disadvantage of dust collection between the display and a transparent foil on the display. |
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This picture shows the second generation display of an HP-42S. There is no foil on top of the display and the bezel has been bent inward to prevent dust collection into the calculator. |
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The Champion series uses a 132 x 32 pixel display. This makes four lines of characters possible. In normal mode, the three upper lines are used for displaying the stack, the bottom line shows the soft key labels. |
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The Champion series can also show simple graphics on the display. This can be a graph or a histogram. |
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The Charlemagne series have a large graphic display of 131 x 64 pixels. This display can show up to 8 lines of text. In normal mode, the four values of the stack are displayed, together with the soft key labels and status information. |
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The Charlemagne display can also be used to display nice graphs and pictures. |
The new LCD calculators
The later calculators of Hewlett Packard use primarily custom designed LCD displays. A nice example of such a display is the display of the HP-20B (Introduced in 2008). This display combines the 7 segment, dot matrix and complete fixed text into one display.
An other nice example is the display of the HP-9G. A dot matrix part on the left used for the graphic views and a combination of styles on the right half.
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