NL1006158C1 - Calculator with dual currency facility, two displays and two keyboards - Google Patents

Abstract

The calculator has two numeric keyboards and two eight digit numeric displays, separated by the conventional arithmetical function keys. The microprocessor in the calculator can perform calculations involving both currencies, e.g. 12 Euros minus 4 Guilders. The conversion factor can be reprogrammed by the user or input via a coded magnetic card. The principle can also be used for calculations in other units of measure, e.g. inches and centimetres, litres and gallons, etc.

Description

-1-

Device for currency conversion.

In many cases there is a need for an electronic device with which numbers can be converted according to a fixed formula. An example of this is a machine with which amounts in one currency are converted to another currency. From 1 January 1999, the need for this aid will become extra strong in a number of countries of the European Union, because these countries will then gradually switch to the new currency, the Euro. A similar tool can also be used to convert between measurement systems (for example, inches and centimeters). Moreover, where two systems are used interchangeably, there is a need to perform calculations using quantities expressed in different units. One wants to know, for example, what one is left with if one hundred guilders and twenty euros are spent. A very user-friendly converter is described in US patent no. 4282514. In this patent, a converter between millimeters and inches is described. In figure 1 the converter is shown as a machine for converting currencies. The machine contains two groups. Each group consists of at least one display and the buttons 0 to 9 and. Each group 25 represents a type of currency. In this example there is a group for guilders and a group for Euros. As soon as a number key is pressed, the number is added to the number in the corresponding display. Immediately after that, the number is converted and the result is shown in the other 30 display. In some cases, the displays are cleared when a new key is pressed: - when the previous key was from the other group.

- when it was more than a certain time ago when a key was pressed (for example 5 seconds) 1006158 -2-

The following example will explain the operation. In the example, the user wants to know how much is 157 euros in guilders and how much is 32.95 guilders in euros. 5 is based on a rate of 2.17 guilders per euro.

euro key golden key euro display gold display 1 1 2.17 10 5 15 32.55 7 157 340.69 3 1.38 3 2 14.75 32 14.75 32.

15 9 15.16 32.9 5 15.18 32.95

A drawback of the converter described here is that one cannot make calculations in which the different currencies are used interchangeably. By expanding the converter with a group of calculation functions (see fig. 2) one can make this kind of calculations. Numbers can then be entered in both guilders and euros and the result of a calculation is also available in both currencies. For example, if 25 people have 15 euros and they spend 12 guilders, it is very easy to calculate with this machine what they have left over. Press 15-12 =: Euro key GLD key Calculation key Euro display GLD display 30 ---------- ----------------- -------------------------- 1 1 2.17 5 15 32.55 15 32.55 1 0.46 1 35 2 5.53 12 = 9.47 20.55 1 0 0 6 1 5 8 -3-

The machine can be expanded with more calculation functions than shown in figure 2, such as root drawing. An additional key can be added to set the 5 currency ratio. The key would also allow you to select the country of the EU and use the pre-programmed currency ratio. Selecting the EU country could be done with a slide switch. Expansion with additional groups of displays 10 and buttons is also possible. This means, for example, that you can calculate with 3 or more currencies at the same time.

The electronics of this device can be built around a 4-bit microcontroller. An example of such a 15 microcontroller is the KS56C220 from the manufacturer Samsung. Two displays could be used with 8 7-segment digits. Each display has 4 common and 16 segment connections. Instead of two displays, one display can also be used on which two groups of 20 numbers are shown. Figure 3 shows a schematic.

Figure 4 shows a flow chart of the program in the microcontroller. A key 25 is always waited for and then the correct operations are performed on the basis of the key. The stack memories mentioned in the flow charts are memories that remember the old value for each display. This value is required to perform the calculations associated with the function keys.

1 0 0 6 1 5 8

Claims (3)

1. Currency conversion device, characterized by at least two groups of number keys 0 to 5 9; one or more displays in which at least two numbers can be shown; a number of arithmetic function keys; control means for adding the number associated with a pressed digit key to the number in the associated display section; conversion means 10 for converting according to a predetermined conversion formula the number shown in one display part and for showing the conversion result in the other display part and vice versa; and calculating means for performing a calculation associated with a function key on pressed digit keys and for converting the computing result into the corresponding numbers to be displayed in the display parts. 2. Device according to claim 1, provided with an operating member and means for changing the conversion formula coupled thereto. 3. Device as claimed in claim 1, provided with an operating member with which it is possible to choose from predefined fixed formulas. 1 0 0 6 1 5 8