Slovakia, having joined the European Union back in 2004, decided to adopt the Euro as its national currency (replacing the Slovak Crown) in 2009. Among other measures (e.g. various transitional periods), the government conducted more than a year long informational campain to help the public in accepting the change. Part of that campaign, an "euro-calculator" (together with some informational brochures) was dispatched to every household. Besides performing the basic arithmetic operations, the calculator was capable of converting any amount between the former currency and the Euro, and vice versa.


According to an archive newspaper article, the cost of this calculator was around 73 eurocents, and two millions of them were purchased and sent out. This represented roughly one quarter of the total sum spent on the whole informational campaign.

After being deployed, there were complaints on the calculators not working, or, even more of them, not performing the expected currency conversion. The government published a method to reset the conversion rate, and offered replacement after mailing in the completely defective units. However, I believe, most people simply put the calculator aside. I of course took on the opportunity and had a look inside the unit ;-) .

Disassembled eurocalculator

The calculator was surprisingly easy to disassemble, as it was held together only by a couple of screws, with no hidden screws and no hard-to-open snaps. Once taken apart, the problem was easily visible - the soldering of battery holder was poor, leading to intermittent power supply to the IC, which caused also the "memory" (conversion value) loss (possibly exhibiting itself when the calculator was handled a bit more roughly).

bad solder joint caused the conversion value loss

Calculators are a prime example of how the modern electronics changed the world. Once they represented the top of the technology, driving in fact the development of the first microprocessor ever; nowadays they are commonplace not even worth mentioning. While there surely still exist top notch calculators, either dedicated or general purpose, the modern universal post-mobile-phone portable electronic devices with large displays and vast computing power made them practically useless. So it appears that only the simplest forms of calculators may survive, either in the form of a toy, or as a specialised device for accountants, facilitating their work with extra large keys and well-readable huge displays.

PCB - component side

The technology used in this particular item reflects its ultra-low-cost nature. Only the "component" side of the PCB is etched from a copper layer. The "contact" side is formed from a carbon-containing material, probably silk-screened, forming the contacts for the keys themselves (with a non-conductive green overlay outside the contacts), and also the vias to the "component" side. The core IC is deviced in the usual ultra-low-cost manner, the bare chip being contacted directly to the PCB's tracks and then covered by a "blob" of black epoxy. There are apparently several solder-jumper options available, but I could find no description of them and brief experimenting did not reveal their function. In the bottom corner of the "component" side contacts labelled "SET" are visible -- these are accessible through a hole in the plastic back cover, covered by a "Q.S. PASS" sticker. These have to be shorted in order the conversion rate be entered. The LCD is connected through a strip conductor (foil) glued permanently to both the PCB and the LCD itself. The keyboard is of the usual rubber single-mold type, with carbon contacts below the keys.

PCB - contacts side

After four years passed, people are already used to the Euro in everyday life, and I believe most of them have already completely forgotten about this calculator.