In the early 1980s, when home computers were just beginning to find their way into households across America, two engineers in North Carolina created something remarkable: an analog interface that could transform a Timex/Sinclair computer into a sophisticated scientific instrument. They called it VOTEM—short for VOltage and TEMperature—and it would eventually find its way aboard the Space Shuttle Columbia.
From Kitchen Table to Outer Space
Ray Mills and Alger Salt didn’t set out to build space-rated hardware. As Salt recalls, “Curiosity was probably the main driver. Ray and I worked together and we both had an interest in electronics. It was a great collaboration.”
Working primarily from Mills’ kitchen table in Greenville, North Carolina, the duo formed Down East Computers and began production of their analog-to-digital converter. The VOTEM was an elegant solution to a common problem: how to get real-world analog measurements into the digital realm of early home computers.
The device used an Analog Devices AD537 voltage-to-frequency converter at its heart—a chip Salt describes as “very versatile and accurate.” Instead of requiring complex parallel data connections to the computer’s bus, VOTEM took a simpler approach: it converted analog voltages into audio frequency pulses that could be fed directly into the computer’s cassette port. The computer would count these pulses over a fixed time period, with the resulting count proportional to the input voltage.
More Than Just a Thermometer
VOTEM came bundled with a temperature probe and could measure temperatures with remarkable precision—sensitive to changes as small as 1/100th of a degree. Reviewer Burt Fisher noted the device recorded a daily high of 79.81°F and a low of 60.07°F, demonstrating its precision.
But temperature measurement was just the beginning. As one review put it, VOTEM opened up “a whole new world (the real world) of applications” for Timex/Sinclair users. The device could be connected to:
- Photocells for measuring light intensity
- Potentiometers for position sensing in simple robotics
- pH meters and spectrometers in laboratory settings
- Weather monitoring equipment
- Strain transducers for measuring forces and stresses
The device even included a bonus feature: a tape signal conditioner that cleaned up the cassette loading signal, allowing users to load programs at lower volume settings with fewer errors—a blessing for anyone who’d struggled with the notoriously finicky tape loading of early home computers.
An Unexpected Journey
Down East Computers sold “a few hundred” VOTEM units, mostly in the US but with international sales as well. Feedback was “mostly very positive,” according to Salt. But one sale would prove extraordinary.
In 1984, a group of twelve students at California State University, Northridge purchased a VOTEM as part of an ambitious project: they wanted to manufacture perfect ball bearings in space. Their experiment would take advantage of zero gravity to create absolutely spherical stainless steel balls—something impossible to achieve on Earth where gravity always deforms molten metal.
The students designed a self-contained, battery-powered unit that could melt small metal alloy cubes suspended in wax. The VOTEM’s role was to monitor temperature inside the experimental apparatus. As the project faced delays and obstacles—including the suspension of NASA’s “Get Away” program following the 1986 Challenger disaster—the original group of twelve dwindled to just four dedicated members: Jeff Craddock and three others who scraped together $8,000, much of it from their own pockets.
Finally, in 1991—seven years after they began—their experiment launched aboard the Space Shuttle Columbia. Though the ball bearing experiment itself failed for technical reasons, the VOTEM successfully measured temperatures in the shuttle’s cargo bay, making it perhaps the most affordable piece of hardware to ever conduct a scientific mission in orbit.
A Remarkable Value Proposition
At $39.95 for the kit or $59.95 assembled and tested, VOTEM was extraordinarily affordable. A competing data acquisition system from Computer Continuum cost around $200, and while more sophisticated, couldn’t match VOTEM’s accessibility for hobbyists and educators.
The kit took about 90 minutes to assemble and came with a comprehensive 35-page manual that started with basic principles and guided users step-by-step through assembly, operation, and calibration. The manual even included sample programs to get users started.
Technical writer Fred Nachbaur, who wrote extensively about VOTEM in SyncWare News, praised its educational value: “Since it’s easy to understand and comes with extras like a tape-signal conditioner, temperature probe and a friendly, very complete text, it is a powerful educational tool.”
Real-World Impact
VOTEM found its way into some surprising applications:
Medical Innovation: Medi Products of Salt Lake City built a system around a TS1000 computer and VOTEM to reclean and resterilize artificial kidneys. The system, which cost $5,000, allowed dialysis patients to reuse a single kidney up to six times instead of once, cutting personal costs from $72 to $14 per month and potentially saving Medicare millions of dollars annually.
Education: Students used VOTEM for science fair projects. In one documented case, a junior high student used two VOTEM units with two computers to simultaneously measure temperature differences between north and south-facing rooms in a miniature styrofoam house, collecting 100 data points over nearly two hours with readings every minute.
Laboratory Research: According to Salt, VOTEM was “used in various laboratory instruments such as pH meters and spectrometers, weather monitors, etc.”
Technical Excellence on a Budget
What made VOTEM special wasn’t just its affordability but the thoughtfulness of its design. The voltage-to-frequency conversion approach allowed users to trade speed for accuracy as needed. Fast sampling (about 350 samples per second) gave 8-bit resolution, while slower sampling (about one per second) provided better than 14-bit resolution—approaching laboratory-grade accuracy.
The device required no modifications to the computer and didn’t use the expansion port, leaving it free for memory packs and other peripherals. All calibration was done in software, making the hardware simple and reliable. As one reviewer noted, the unit was “made of quality components” and demonstrated Down East Computers’ commitment to using “only high quality components.”
A Legacy of Innovation
VOTEM represents a remarkable moment in computing history—a time when small companies could create innovative products that punched well above their weight. From a kitchen table in North Carolina to the cargo bay of a space shuttle, the VOTEM demonstrated that thoughtful engineering and attention to user needs could create tools that opened up new possibilities for hobbyists, students, and researchers alike.
The device may be long obsolete now, replaced by USB data acquisition modules and Arduino-compatible sensors. But the story of the VOTEM—and especially its journey to space—reminds us that great innovation doesn’t always require massive budgets or corporate backing. Sometimes it just takes two curious engineers, a good idea, and the determination to see it through.
As Salt concludes his recollection: “It was a great collaboration.” Indeed it was—one that extended the reach of home computing from earthbound hobbyist pursuits all the way to the stars.