Electrical and Computer 
Thumbnail of page image            Design Descriptions
Micrometer Data Capture Front Panel
Clip on BAT Robotic Arm

Strain gauge amplifier
A device based on the characteristics of a Wheatstone bridge circuit,  whereby the resistances in three arms are reference values, and the resistance in the fourth arm is provided by a long wire rigidly attached to a structure such as a bridge span member.  As the wire is stretched, the change in its resistance is represented by a flow of current across the center of the circuit, providing a realtime measurement of the subtle differences in the length of the wire, and thus of the structure. 
This product needed to be stable across a broad range of conditions including, but not limited to, variable power source, extremes of ambient temperature, altitude, and vibration.
Mail Monitor emissary
The Mail Monitor System was devised to track the flow of mail through the Postal network.  At several locations within the post offices, there were stations at which a microwave transmitter was positioned, in order to interrogate the mail stream as it passed by.  A standard business-sized envelope bearing a letter-slim,  unpowered responder was deposited into the mail system, just as if it had been a normal letter, but as it passed each interrogation station, it would rectify the microwave signal it received, use the rectified energy as a power source, and respond to the interrogation (at a lower frequency) with a unique code.  In this manner, it could be determined when a particular piece of mail passed a specific station, without any noticeable change in the mail itself. 
I assisted with the design and development of the tiny emissary units which were mailed in the envelopes.
Telephone toll call inhibitor
Before the phone systems became as versatile as they are today, it was difficult for institutions to block calls which incurred extra charges.  Hospitals, correction facilities, schools, and businesses were eager to alter their instruments so that outgoing calls could be limited to non-toll connections.  Our device was small enough to fit inside the phone to prevent tampering, and could be "unlocked" by a code, for use by authorized personnel.  
Spectroscopic peak detector
This turnkey MIMIC determined the peaks in the output from a spectrophotometer, by an adjustable algorithm, before recording the data from the experiment.   
Custom marginal punched card
At a time when sorting large quantities of data was a physical act, I redesigned a marginal punch card to adjust and normalize the distribution of  active positions based on letter-use frequencies. 
A marginal punch card resembles a common file card except that  it bears holes all around its periphery. Certain holes (for example,  those representing the first three letters of the subject on the card) are cut away so that there is a path from the hole to the edge of the card.  When a rod is slipped through a hole (or several rods through several holes) in a stack of the cards, all those cards which do not have that position punched out remain on the rod, while the target cards fall out of the stack.  The cards could be indexed by several factors, which is difficult to achieve with a standard filing system.
Stereopret to HP calculator interface
By eliminating tedious transcription, this MIMIC  improved data gathering reliability, efficiency, and effectiveness, while increasing operator job satisfaction, by directly conveying information from the stereo image interpreter to the calculator, eliminating the errors which often accompanied human input.  
Thermoelectric Cooling Control Unit
A high power device for dual solid state cooling, designed to maintain very low temperatures within extremely tight limits.  In one application, it was used to freeze and control the temperature of soil samples during experimental testing.  
Cardpunch to HP calculator interface
The electrical environment of the IBM 029 cardpunch was extremely hostile to delicate semiconductor components.  The I/O for this MIMIC used a large array of reed relays, which when coupled with  the evolution of attrition and replacement, provided a reliable connection to the 029 for the programmable interface to the Hewlett Packard calculator.  The unit was in use 24 hours a day, 7 days a week, for many years (and was reported to be still in service the last time I had contact with the customer), and after an initial few months of replacing relays as they became damaged, no further components failed.  
Multiprocessor control system for an Analytical Plotter
This was a major project which included an extensive retrofit to an existing device (a number of units were modified, for a variety of customers), as well as the complete design of a new device to replace the existing mechanical methods of data gathering. 
In the retrofit, expensive mechanical hardware which needed to be maintained at incredibly tight tolerances was replaced by computer-controlled servo motors and optical encoders.
Switchable Character Set control module for TI733 terminal
This was my first project as Tarot Electronics.  It was necessary to fit large components into a very small space, so my novel approach of reducing PC board track real estate by putting some of the components (memory) on the back of the board, made it possible to provide this feature for the 733, when all other approaches had failed.  
MIMIC®, a Mutable InterfaceTM and one-board computer, with its support modules, including but not limited to memory, clock/calendar, data acquisition, motor control, and analog I/O.
The MIMIC®  logo was applied to a variety of custom interfaces, turnkey systems, avionics, and personal computers which contained the micro-computer based modules.  
MIMIC has its own page.

Video switch
Fluidic amplifier
In my third year project, I built a transistor-like pneumatic device out of aluminum and plastic, and created a number of interchangeable parts, to measure the characteristics as component sizes and configurations changed.  When I had established sufficient gain, stability, and control, my device was used as a model by NRC to produce brass and steel production versions which were put into service.  Similar devices are used, today, in automobiles and aircraft.  
Frame time decoder
The time and date data from the Hermes satellite feed arrived at the ground station in a cryptic format which needed to be converted before being displayed for human interaction.  
Character count detector
At one time, TI-733 terminals would lose the last character of every line.  By detecting the 79th character, and capturing  the following inputs as they came in, saving them until the carriage return was complete, the data loss was averted.  The challenge was in fitting the circuit into the tiny space which was allocated for the device, and in fitting the firmware into the tiny data space which was available.  
Computer to plotter data switch
Stepping motor switching module
Lots of high current switches, lots of heat sinks, lots of computer controls.  
PDP-8E downgrade modification
The original configuration of the Hermes Ground Station had a number of devices which were designed to depend on timing signals from inside the pair of PDP8i computers which were originally part of the facility.  When a newer, faster, PDP8e was purchased, it was discovered that some of the custom designs had incorrectly counted on undocumented clock signals which were never intended for interfaces, and which had been eliminated (for many of the operations) in the new computer, to improve speed.  Rather than try to understand all of the legacy interfaces (in the absence of their designers) well enough to reconfigure them, I undertook the task of providing the PDP8e with a lobotomy, reverting its motherboard clock timing to the PDP8i protocol.  
Solid state head temperature gauge
This design is founded on the temperature characteristics of a common diode.  
Avionic photogrammetric display generator
Integrating data from a number of aircraft sensors, this device generated a red LED display which was exposed onto the next frame of film, providing information about the conditions under which the photo had been taken.  This method of  locking the orientation, speed, distance, etc, to the stereo frames as they were exposed, reduced the possibility of transcription errors.  The problem of limited space was solved by creating a set of interconnected  printed circuit boards which folded into their tiny box like the paper on a Japanese fan.  
Washable input device for fish measurement
We were asked to build a computer which would take voice commands (because the equipment then in service had acquired an unacceptable aroma), but at the time that task would have been prohibitively expensive, if it had been possible at all.  Instead, I designed a vernier caliper with a direct input to the computer, a foot switch to activate the data transfer, and a washable keyboard.  
Two dimensional micrometer data capture device
Using optical encoders, with a custom frame and armature, it was possible to provide data directly from a micrometer to the computer.  A second linear dimension was included. 
A third dimension was commissioned from another supplier, but it was not successful.
MC68000 based module for multiprocessor applications
It is possible and convenient to slave Motorola 68000 series microprocessors to Intel 8080 series chips, and in this way, each hardware module can have its own independent processing while being coordinated with the other hardware in the system.  An 8080 can be slaved to a 68000 with somewhat more difficulty. 
The Motorola 6800 series microprocessors were not suitable for our multiprocessor applications, making neither good masters nor good slaves.
Photogrammetric stereo interpreter motion control system
A unique hinge
Tent fly power supply
UNREALTM  a performer servo-system
Fantasy® (patents 1981) a curved, performer supported keyboard
Fantasy has its own page   
MicroTerminalTM  a hand-held data entry device for small computers
BATTMBackloop Audition for Telerobotics, an auditory substitute for haptic controls
The BAThas its own page.   
InchWurmTM an improvement to the locomotion method of a CMU space station inspection robot 
Copyright ©1998, 2000, 2002 JB Tait  980227.1830 LM020529.0945