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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Circuit identified malfunctioning photovoltaic array. Cell-failure detection circuit compares output of photovoltaic array to control cell. If any module fails, activates light-emitting diode. Circuit could also sound alarm.
Central array of light-emitting diodes displays status of 30 video cassette recorders (VCR's) monitoring integrated testing of Space Shuttle. Remote status panel linked to VCR's by one 37-conductor cable. Transistor/ transistor logic chips in interface circuit allow LED array to function without drawing power from VCR control circuits.
The minority carrier diffusion length Ln in the base or substrate region is an important parameter which governs a solar cell's performance. The present investigation is concerned with the development of a multiwavelength analyzer (MWA) technique for the nondestructive spatial testing of polycrystalline solar cells. The MWA method is based on the utilization of the short-circuit current generated by two or more light-emitting diodes (LEDs) operating at different wavelengths and modulated 180 deg out-of-phase. For a determination of Ln by the MWA technique, it is necessary to know the value of the absorption coefficient.
Images of retinas examined for characteristic patterns. Color photographs of retinas taken. Proper alinement of eye obtained by asking subject to gaze at light-emitting diode. "Red-eye" patterns in resulting color photographs examined by trained observers for signs of ocular defects. System used to check power of contact lenses and eyeglasses by taking photographs with these items in place.
Position sensor and mirror guides manipulator toward object. Grasping becomes automatic when sensor begins to receive signal from reflector on object to be manipulated. Light-emitting diodes on manipulator produce light signals for reflector, which is composite of plane and corner reflectors. Proposed scheme especially useful when manipulator arm tends to flex or when object is moving. Sensor and microprocessor designed to compensate for manipulatorarm oscillation.
An optical proximity sensor for optically detecting an object within a predetermined detection volume is described. More specifically, an optical proximity sensor is disclosed having an illuminator assembly including lens and a plurality of light-emitting diodes located at first predetermined positions along the focal plane of the illuminator lens. A detector assembly including a detector lens and a plurality of photodiodes located at second predetermined positions along the focal plane of the detector lens is also provided. The two lenses are spaced apart a predetermined distance in order to define a predetermined detection volume. Additionally, a combination of optical proximity sensors, according to the invention, is disclosed wherein the sensors can be used in conjunction with a vehicle to provide a safety system for warning an operator when an object is within a volume defined by the proximity sensor combination.
Remote displacement measurement is demonstrated using a Fabry-Perot cavity with a multimode optical fiber link. The sensing cavity modulates, as a function of its length, the spectrum of a light-emitting diode (LED). The light returns via the fiber and is analyzed by a tunable reference cavity. A closed-loop control causes the reference cavity to track the sensing cavity length within 2 x 10 to the -12th m. Displacement range is 2 x 10 to the -6th m. The reference cavity length is measured interferometrically, using a laser, to obtain the sensing cavity length. Advantages of this sensing technique include compatibility with multimode fiber-optic components, high immunity to optical losses, and large dynamic range.
Instrument includes gallium arsenide light-emitting diode (LED) and silicon phototransistor with infrared filter, all cast in single plastic housing. Housing attached to subject's face with transparent doublesided adhesive tape. LED directs pulses of infrared light to skin, which reflects them to phototransistor. Phototransistor produces signal that is processed by external circuits to yield plot of infrared reflectance with time. External circuits temperature-compensated and respond only to pulsed component of detector output, rejecting those components caused by stray light. Circuits also extract blood-volume pulse amplitude and heart rate.
GaAsP on GaP top solar cells as an attachment to silicon bottom solar cells are being developed. The GaAsP on GaP system offers several advantages for this top solar cell. The most important is that the gallium phosphide substrate provides a rugged, transparent mechanical substrate which does not have to be removed or thinned during processing. Additional advantages are that: (1) gallium phosphide is more oxidation resistant than the III-V aluminum compounds, (2) a range of energy band gaps higher than 1.75 eV is readily available for system efficiency optimization, (3) reliable ohmic contact technology is available from the light-emitting diode industry, and (4) the system readily lends itself to graded band gap structures for additional increases in efficiency.
Full-color, matrix-addressed electroluminescent display uses three different color phosphors located in two separate, superimposed layers to provide higher brightness, better contrast ratio, and higher resolution. Design used for such transparent, flat-panel display media as thin-film electroluminescent phosphors, liquid crystals, or light-emitting diodes.
Proposed optoelectronic system guides blind people to important locations in public buildings, With system, sightless person easily determines directions and distances of restrooms, water fountains, stairways, emergency exits, and elevators. Circuitry uncomplicated and inexpensive, in both transmitter and receiver. Readily-available light-emitting diodes, photodiodes, and integrated-circuit chips used to build locator aid for the blind.
Programmable Display Pushbutton (PDP) is pushbutton device available from Micro Switch having programmable 16X35 matrix of light-emitting diodes on pushbutton surface. Any desired legends display on PDP's, producing user-friendly applications reducing need for dedicated manual controls. Interacts with operator, calls for correct response before transmitting next message. Both simple manual control and sophisticated programmable link between operator and host system. Programmable Display Pushbutton Legend Editor (PDPE) computer program used to create light-emitting-diode (LED) displays for pushbuttons. Written in FORTRAN.
Light flashes on to indicate high current. Simple, inexpensive display circuit indicates when 3,000-A welding current flows in welding gun. Onset of welding current induces voltage and current in 1,000-turn, 28-gauge copper-wire coil. Single-transistor amplifier amplifies induced current, energizing light-emitting diode (LED) connected to collector of transistor. Light from LED gives simple, direct indication of welding current.
Control circuit operates two independent stepping motors, one at a time. Provides following operating features: After selected motor stepped to chosen position, power turned off to reduce dissipation; Includes two up/down counters that remember at which one of eight steps each motor set. For selected motor, step indicated by illumination of one of eight light-emitting diodes (LED's) in ring; Selected motor advanced one step at time or repeatedly at rate controlled; Motor current - 30 mA at 90 degree positions, 60 mA at 45 degree positions - indicated by high or low intensity of LED that serves as motor-current monitor; Power-on reset feature provides trouble-free starts; To maintain synchronism between control circuit and motors, stepping of counters inhibited when motor power turned off.
Simulator replicates, kinematically and dynamically, mating of large, massive mobile structure with similarly large and massive fixed structure. Developed for testing berthing-and-latching mechanism. Fixed section holds active berthing-and-latching mechanism and its motor control system with optical encoder to maintain synchronization among four latches in mechanism. Tripodal load-cell network gathers data on load history of berthing operation, and infrared tracking system including light-emitting diodes produces data for position history.
Optoelectronic terminal for digital communication both transmits and receives over single optical fiber. Uses same semiconductor device - light-emitting diode (LED) - as both transmitting and receiving transducer. Dual-purpose LED's reduce cost.
An experimental study was performed to determine the effects of vibration on the propagation of light through SMA- and ST-type fiber-optic connectors. A multimode, fiber-optic link was vibrated from 0 to 10,000 Hz at a constant peak acceleration along the connector transverse and longitudinal axes. All other environmental parameters were ambient. Transfer characteristics through the connection were examined as a function of vibrational frequency using both laser and light-emitting diode (LED) light to illuminate the system. Slight differences in operation between the SMA and ST connectors were observed with no appreciative attenuation as a result of vibration. Vibration did cause the constant-amplitude input light to be modulated in the connector; however, the amplitude of vibration-induced noise was less than 3 standard deviations from the mean.
Future aircraft will use fly-by-light control systems with fiber-linked optical sensors for such measurands as temperature, pressure, and linear and angular position. A digital optical sensor is described which was developed to transmit the angular position of such slowly rotating parts as a throttle of fuel flow control valve on an aircraft. The sensor employs a reflective code plate with ten channels providing a resolution of 0.35 degrees. Two light-emitting diodes with overlapping spectra are used as light sources. A single microoptic multiplexer-demultiplexer composed of a GRIN rod lens and a miniature grating is used to disperse the spectrum and recombine the spectral components from each channel after reflection by the code plate. The results of preliminary environmental tests of this unit are discussed. The sensor has been operated for brief periods of time between -60 C and +125 without adverse effects. Preliminary vibration tests indicate that the unit will work properly at the maximum vibration levels expected in a jet-engine environment.