Teardown | Calculators

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INTRODUCTION

Technology evolves at an exponential rate, every now & then a new product hits the market, manufacturers use terms like upgraded design, low-cost & enhanced experience in their marketing strategies. An average user’s perception of how the design is upgraded, the cost reduced & the experience enhanced does not immediately reflect the engineering decisions made during the product development or design iteration. Most often, it becomes difficult to understand why and how things change the way they do, multiple parameters affect the design evolution of products throughout their life cycle, the creative decisions made by the designers & engineers, consumer affordability, technological advancement at the time & the value of the product.

This comparison between two calculators helps us understand how product design & manufacturing considerations can vastly differ from the time of introduction to the time of saturation for a product with the same basic functionality & purpose across nearly 5 decades.

“September 2018, I was on a vacation in Istanbul taking a midday stroll through the modern day Constantinople. While my friends were busy shopping for souvenirs at Grand Bazaar, I caught sight of this beautiful calculator sitting by an old man at a jewelry store, after 10 minutes of intense convincing & negotiation, the Turkman finally agreed to sell it to me. 58 streets, 4000 something shops under one expanding roof and I walk out of there with a steal deal on a 47-year-old Olympia CD-80 in perfect working condition.”

Olympia CD-80

The Olympia CD-80 is one of the most stylish calculators offering space-age looks for what is a modest calculator by function, with gentle curves & fillets marking out the exterior, the CD-80 definitely stands apart from other calculators of its era when it comes to looks. This calculator is a handful & offers the satisfaction of gripping a weighted object.

Sold only in Germany, the Olympia CD-80 is an OEM variant of the Panasonic JE-850U manufactured by Matsushita Panasonic in Japan from 1972 to 1973.

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DISPLAY

The CD-80 is an 8-digit calculator with nine 8-segment VFD (Vacuum Fluorescent Display) manufactured by Digitron. VFDs were a prominent display technology at the time and widely used in electronic equipment, the VFD on this calculator was a bit more unique for its additional 8th segment that only lit-up when the number “4” was displayed. The first VFD in the row displays information such as low battery indicator, negation & error.

KEYPAD

The keypad holds 10 numeric keys & 8 function keys which offer a soft, damp, springy feel when pressed. Unlike most other calculators, the CD-80’s keypad uses reed switches which are hermetically sealed in a glass bulb, each key has a small magnet that toggles the reed switch ON/OFF. This prevents oxidation on contact pads, improving operational reliability & robustness against dust & physical abuse.

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TECHNOLOGY

Inside its stylish exterior, the most distinctive feature of the CD-80 has to be the PCBs; they’re beautiful hand-drawn, double sided circuit boards. The electronics incorporate a modular design that combines the keypad & display module with the motherboard using high-quality gold-plated connectors. The CD-80’s logic processor is a Texas Instruments TMS0122NC, a 16-pin DIL package silicon chip. The unique “7305” marking on the IC indicates the manufacturing period May 1973. The circuit board features an over-current protection fuse, a large number of 3-pin transistors to control the VFD and some passive components.

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CONSTRUCTION

Plastic injection moulding wasn’t a new thing back in 1972, the same year PET water bottles started mass producing. The CD-80 has a two-part plastic injection molded body which is snapped together at four points and secured in place with a single screw which can simply be unscrewed using a coin.

The white front cover combines two plastic pieces, the transparent polycarbonate display window and the black keypad deck. The back plastic cover features a recessed receptacle to accommodate the battery pack. Both the rechargeable & replaceable battery packs seat flush with the back cover following the exterior contours with press-release snap locks on the sides.

The modular electronics of the calculator are secured using four screws through the mounting holes in the keypad. The four 2.5mm metric screws are fastened into brass thread inserts that are insert moulded as a part of the front cover. The use of such fastening features, although expensive, indicate that the CD-80 was designed for multiple assembly/disassembly cycles in the event of maintenance or repair.

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POWER SOURCE

The calculator label mentions a rating of 6 volts, 1 watt; it can operate with three different types of power sources ranging from about 4.8 to 5.2 volts, a rechargeable Ni-Cd battery pack [JL-032], an additional battery tray [JL-012] that accepts four “AA” size cells and a 7W AC adapter [NLG80S].

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KEY FEATURES

  • Space-age aesthetics for its time.

  • Plastic injection moulded enclosure

  • Vacuum fluorescent tube display

  • Rechargeable & replaceable battery packs

  • Optional AC power adapter

  • Reed switch keypad

  • Design for Serviceability

COST

At the time of sale: $220 (INR15,500) [At the time of sale]

CONCLUSION

Clearly, there were no corners cut with the Olympia CD-80. It’s from a time when hand calculators were trending & rapidly evolving technology, it used advanced electronics, the exterior design & ergonomics are radical for its time. Its flawless operation nearly 46 years after manufacturing is a testament to how solid this calculator was designed & manufactured.

Casio MJ-120D

The Casio MJ-120D is a typical modern-day desk calculator, inexpensive & handy. It’s 2019, calculators are more utilitarian than trendy nowadays. The MJ-120D is not necessarily appealing or repelling, it just another essential desk object that exists to make our everyday life easier if we’re crunching a lot of numbers. Although, it might scream Made In China all over, it’s mass manufactured in the Philippines and sold globally by the popular Japanese electronics company, Casio Computers. The tear-down of this calculator is less intriguing than the Olympia CD-80, but what is more intriguing is the 47 year long evolution of the humble hand calculator that this presents. A lot of things have changed -- user perception, functionality, affordability, usability, manufacturability and technology. Their purpose, however, remains the same.

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DISPLAY

The MJ-120D comes with a 12-digit, 6-segment trans-reflective LCD [Liquid Crystal Display] panel, the starting segment of the display is subdivided into different parameters that indicate calculation step, GT (grand total), error and negation. Trans-reflective LCDs consume very less power to operate while offering excellent visibility because of their high contrast ratio. The technology is standardised and customization for mass production is possible which makes it an ideal choice for inexpensive, low-power consumption devices.

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KEYPAD

The keypad on this calculator is simple by design and function. It has 35 keys, that is twice the number of keys in comparison with the CD-80. The operation is mechanical & direct contact, an elastic rubber membrane with conductive pads is used between the plastic keys & electronic contact pads integrated as a part of the main PCB’s copper traces. When a key is pressed, the flexible projections on the elastic membrane shorts the contact pad on the PCB signalling an input. The key-press feels tactile and hard-landing. The design is functional, simple, inexpensive for mass production & assembly.

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TECHNOLOGY

The MJ-120D runs on a custom silicon chip, the silicon die is directly embedded onto the dual layer PCB and protected with a blob of black potting material. The electronics design of the calculator is highly integrated to simplify manufacturing & assembly. The LCD panel and the photovoltaic cell are connected to the motherboard which also contains the keypad & the cell holder. The LCD is connected using a flexible, conductive film that’s fixed to the pads on the motherboard using conductive adhesives as an inexpensive, scalable solution.

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CONSTRUCTION

Like most mass produced, low-cost electronics, the MJ-120D also comes with a plastic injection moulded enclosure. The outer casing is a two-part enclosure with multiple snap features around the edges & two self-tap screws securing them in place, the top cover has numerous cutouts for the display, photovoltaic cell & input keys. The back cover features recessed screw mounting features & rubber feet.

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POWER SOURCE

The MJ-120D run on two sources of power, a replaceable 3V LR44 Lithium cell being the primary source of power & a secondary 3V photovoltaic cell. The electronics & technology used enable the calculator to operate on very less power, lasting a long time on the small cell. The secondary photovoltaic cell can power the calculator in well lit environments in case the cell runs out of charge. This makes the calculator very reliable and versatile.

KEY FEATURES

  • Plastic injection molded enclosure

  • High-contrast display

  • Inexpensive & affordable

  • Long battery life

  • Solar power

  • Disposable

COST

At the time of sale: INR 400 [At the time of sale]

CONCLUSION

In comparison with the Olympia CD-80, the recent-day Casio MJ-120D presents a very elaborate & distinctive understanding of how technology has evolved from the period of introduction to period of saturation in this everyday-product, the concept of design for serviceability and the design of mass manufactured disposable electronics.

COMPARISON SUMMARY

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