DATAMATH CALCULATOR MUSEUM
|Date of introduction:||January 1974||Display technology:||LED modules|
|New price:||$44.95||Display size:||8|
|Size:|| 6.1" x 2.9" x 1.0"
154 x 74 x 25 mm3
|Weight:||5.0 ounces, 142 grams||Serial No:||632842|
|Batteries:||4*AA Alkaline||Date of manufacture:||mth 06 year 1974|
|AC-Adapter:||Origin of manufacture:||Japan|
|Memories:||Displays:||8-Digit COB Module|
|Program steps:||Courtesy of:||Joerg Woerner|
Canon introduced in January 1974 with the LE-83 their first calculator with an MSRP (Manufacturer's Suggested Retail Price) below $50. While we consider the LE-83 and its stablemates as members of the 4th generation of Canon's product portfolio of Portable Handheld Calculators with LED display does it reuse with the TMS0101 single-chip calculator circuit some technology of the 2nd generation LE-80:
• 1st Generation:
• 2nd Generation: LE-80, LE-80M, LE-80R, LE-82
• 3rd Generation: LE-81M, LE-100, F-5, FC-80
• 4th Generation: LE-83, LE-84 and LE-85
With the MSRP of the LE-80 in 1973 still around $100, Canon's engineering team needed to dig deep into the cost-reduction toolbox while designing the $50 LE-83 and it shows! Canon decided to use with the TMS0701 the 2nd generation of the TMS0101 chip which allows to drive the segments of the LED display directly. Having the LED display in 1974 as the main cost driver of portable calculators, Canon opted for an 8-digit display and one additional discrete round LED for the minus sign instead the 9-digit display used with LE-80 but missed changing the code of the TMS0101. With the TMS0101 clearly developed for displays with a leading 9th digit and Canon using just a discrete LED to the right of the 1st digit instead a full character instead, the LE-83 expressed some strange behavior:
• Negative numbers with 1 to 7 digits show a minus sign to the left of the number|
• Negative numbers with 8 digits show a minus "dot" to the right of the number
• Overflow of the calculating result, displayed with the TMS0101 as or on the 9th digit isn't shown!
Canon's engineering team fixed this flaw with the LE-84 and LE-85 using two different approaches, consequently creating a rather divers portfolio:
Dismantling the featured Canon LE-83 manufactured in June 1974 by Canon in Japan reveals a rather compact design with three printed circuit boards (PCBs) for main electronics, display, and keyboard powered by four disposable Alkaline batteries. The Main-PCB is centered around a Texas Instruments single-chip calculator circuit and supported by a myriad of discrete components:
• Calculating Unit -
TMS0101 (TMS0701) single-chip calculator circuit
• Display Driver - No Segment Drivers and discrete Digit Drivers with two Transistor Arrays
• Clock signal generation for TMS0101 with discrete components
• Power converter with discrete components and transformer
• 17-pin connector to the Display-PCB (16 pins used)
• 20-pin connector to the Keyboard-PCB (18 pins used)
Calculating Unit: The LE-80 makes use of a 2nd generation TMS0101 single-chip calculator circuit, also known as TMS0701 and derived from the TMS1802, better known as first "calculator-on-a-chip".
Display: Texas Instruments introduced together with the TMS0100 calculator chip two pre-configured LED (Light-Emitting-Diode) modules (DIS40, DIS95) based on the TIL360 arrays and the corresponding segment drivers (SN75491) and digit drivers (SN75492). Most early 8-digit designs like the LE-80 made use of these parts exhibiting two disadvantages:
• SN75491, SN75492 - Limited to designs with 5 or 6 batteries
• TIL360 - Cost driver number one in the calculator design
Texas Instruments consequently introduced with the SN75493 and SN75494 revised display drivers optimized for designs with 3 or 4 batteries but the true innovation could be observed with the technology how to manufacture the 9-digit LED displays used with early four-function calculators:
• 1972: Two Hermetic Multi-Digit Calculator Numeric Seven-Segment LED Displays soldered onto
• 1973: Nine Seven-Segment LED Displays soldered onto a PCB
• 1974: Nine Seven-Segment LED Display Chips bonded onto a PCB
• 1975: Nine small Seven-Segment LED Display Chips bonded onto a PCB with additional magnifying lens
• 1976: LED Displays near extinguished by VFD and LCD technology
On the tireless, never ending quest to squeeze the last penny out of the manufacturing costs of electronic calculators, Canon went with the LE-83/LE-84/LE-85 in 1974 through four different display technologies:
• Display Type 1: Eight-Digit
display module with eight Monsanto MAN-3A Seven-Segment LED Displays soldered onto a PCB
• Display Type 2: Nine-Digit display module with eight small Seven-Segment LED Display Chips bonded onto a Ceramic Substrate with additional magnifying lens - ANTEX SK-3-307
• Display Type 3: Nine-Digit display module with eight small Seven-Segment LED Display Chips bonded onto a PCB with gray masking and additional magnifying lens - unknown manufacturer
• Display Type 4-8: Nine-Digit display module with eight small Seven-Segment LED Display Chips bonded onto a PCB without masking and additional magnifying lens - Rohm Semiconductor LAB-B-2/8
• Display Type 4-9: Nine-Digit display module with nine small Seven-Segment LED Display Chips bonded onto a PCB without masking and additional magnifying lens - Rohm Semiconductor LAB-B-2/9
The featured LE-83 manufactured in June 1974 makes use of an unknown Nine-Digit display module with 8 Seven-Segment displays chips bonded onto a PCB and magnified with a clear plastic lens. The display module is connected with 16-pins to the Main-PCB. The leftmost Digit is not populated and therefore not connected to the Main-PCB.
Display Driver: The Main-PCB of the featured LE-83 manufactured in June 1974 makes use of nine Transistors with supporting Resistors as discrete Digit Drivers for the LED display while the TMS0701 chip drives the Segments directly. Although the layout of the PCB would support discrete transistors for the Digit Drivers, uses this LE-83 two Transistor Arrays TA1 and TA2 with four, respective five transistors bonded and encapsulated into a small module.
Clock: While the nominal clock frequency of the TMS0700 single-chip calculator circuit is specified with 250 kHz, uses the LE-83 a much slower pace to reduce overall power consumption of the product slightly. The astable multivibrator using two discrete transistors operates at a frequency between 100 kHz and 150 kHz, we observed with the featured LE-83 manufactured in June 1974 a clock frequency of 132 kHz.
Power Supply: The LE-83 is powered by four disposable Alkaline batteries resulting in a typical voltage between 4.0 V (completely depleted cells) and 6.0 V (new cells). The Main-PCB hosts a power converter circuit centered around an astable multivibrator, step-up transformer, diodes and capacitors to generate the VGG supply voltage for the TMS0701 chip and the clock oscillator while the VDD voltage is derived directly from the four batteries. We observed in the featured LE-83 manufactured in June 1974 consequently a rather low supply voltage of VDD = -6.0 V and a normal VGG = -15.2 V for the electronics and measured the current consumption with:
VBAT = 6.0 V
|Calculating||0||26 mA||132 kHz|
|Calculating||88888888||59 mA||132 kHz|
Keyboard: The keyboard of the LE-83 uses spring-supported plastic keys pushing a small conductive rubber element against two contacts etched on a single-sided phenolic PCB combining both long-travel keys with reasonable manufacturing costs while maintaining longevity of the calculator. The keyboard module is connected with a short 18-pin flat-cable to the Main-PCB.
Here at the Datamath Calculator Museum we classify the featured LE-83 as Display Type 2.
The LE-83, LE-84, and LE-85 introduced in 1974 marked the last generation of calculators with LED displays in Canon's portfolio of Portable Handheld Calculators and the next product named LD-80 was sporting a green VFD (Vacuum-Fluorescent-Display) instead.
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© Joerg Woerner, December 5, 2001. No reprints without written permission.