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Fulcrum Trackball Plus

Posted: 03 May 2020 21:09
by Archie
Ball size: 13/4" (44.45mm)
Interface: RS-232
FCC ID: FGK5AD TRACKBALL

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Quite interesting device, developed in 1986. At those times, standard trackballs & mice were equipped with two or three buttons - but Trackball Plus has six! Capability to emulate other devices was also impressive: eight (or ten; sources vary) modes, including not only pointing devices but also graphical input peripheral like tablets, digitizers etc. All this functionality was implemented in hardware, controlled by predefined button combinations. In 1987-88 it was a winner of PC Magazine editor's choice.

Electronic part is really complicated: main chip is Intel P8031 (in datasheet it was even described as "microcomputer"), with separate Intel D2764-2 UV-erasable memory. Looks almost like PC XT board with CPU and ROM BIOS! No surprise it requires its own power supply, as COM port is unable to provide so much current. Other chips on board (made by Seiko) are Motorola 74LS373 3-state latch, MC14584B Schmitt trigger and MC7805CT voltage regulator.

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Mechanical design is also remarkable. Three NMB R-4HH ball bearings are used. X and Y axis ones are surrounded by plastic drums ending with perforated flanges having 36 triangular slots. The ball touches outer surface of drums. Due to the big diameter of drum, resulting resolution is quite low: just 84 PPR (15 CPI). In 1990 PC Magazine ad, it was mentioned that new version with higher resolution should be made - but it seems something went wrong with new model, and the company itself...

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As received, just one out of 3 bearings was not rotating smoothly, but cleaning & re-lubrication fixed that. Whole assembly is mounted on 3 coil springs in case, providing kind of suspension. White ball is very light (just 45.8g), but despite of that spins quite well.

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Button switches made by ITW are of interesting type: something like membrane switch, but with unusual shape of contact. Actuation force is bigger than Omron-style microswitch; short travel with loud click and crisp feel, kinda like simple tact button. Currently such type is not present in ITW product catalog, but it resembles Series 39 externally. They were unpleasant to use initially, needing exactly vertical pressure and jamming otherwise - but after disassembling, good cleaning & lubrication become very nice. Biggest problem is, the contact is unreliable: if pressure is reduced, they disconnect before tactile "back-click" occurs.

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Overall design of casing is similar to the Wico Corpration "Command & Control" and Marjac Limited "Joyball" trackballs released several years earlier (1982-83 probably) and well known to the Atari and Commodore users: the same simple box with rounded corners and the ball in center. Pretty common fashion of '80 era:
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Upon closer examination though, it's turned out the actual predecessor was another trackball designed for Atari and other similar home computers: the "Accuball Controller" by Accu Company. Identical mechanics, ball, drum-shaped quadrature sensors, bearings, etc. Case was slightly reworked to accommodate more buttons (original Accuball was a single-button device), and of course, totally different electronics board implemented. Looks like Fulcrum either acquired the manufacturing tooling from Accu, or bought existing stock of trackball internals from them (or their supplier). Note the same secondary PCB: even contact grid for Accuball conductive rubber button is still present, while 18-pin OMX 2004 chip, not needed anymore, is not soldered:

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Asymmetric arrangement of buttons looks interesting: probably some attempts to make it ergonomic were undertaken, but as a pointing device for Windows it isn't really convenient. Usability issues were mentioned in various reviews published back in '80s as well.

In Microsoft serial mouse mode, the first button is LMB and second - RMB, while fourth works as a click-lock latch: button pressed after it become locked until next click. Fifth button (marked "A" in documentation) was special "alternate cursor" switch for AutoCAD software.

Emulation modes are switched by pressing of first, second, third and the last (sixth, but referred to as "5" because of mentioned "A" designation of actual fifth one) buttons, followed by selection button. E.g., to put it into Microsoft mode, press buttons 1,2,3,5 simultaneously, then press button 3. It was also possible to switch the modes via software commands.

Device was reviewed in 1986...1990 in PC Magazine, BYTE, Modern Electronics, Compute!, S-100 Journal, and Radio-Electronics magazines:
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Nowadays, connecting to the modern PC requires whole set of adapters - but despite of mentioned shortcomings, this more than 3 decades-old device still works fine! Of course, it was used to write this article.