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Results for “SWITCHING CIRCUIT”

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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At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

CMOS output buffer wave shaper

As the switching speeds and densities of Digital CMOS integrated circuits continue to increase, output switching noise becomes more of a problem. A design technique which aids in the reduction of switching noise is reported. The output driver stage is analyzed through the use of an equivalent RLC circuit. The results of the analysis are used in the design of an output driver stage. A test circuit based on these techniques is being submitted to MOSIS for fabrication.

Albertson, L.↗
NASA NTRS2001

Effects of AEA Cell-Bypass-Switch Closure on Charged EOS-Aqua NiH2 Cell

The nominal performance of AEA CBPD under simulated EOS-Aqua/Aura flight hardware configuration has been demonstrated. There is no evidence of cell rupture or excessive heat production during or after CBPD switch activation under simulated high cell impedance (open-circuit cell failure mode). Inadvertent CBPD switch activation with a charged cell (low impedance path) intermittently closes and opens up the switch, therefore the device may or may not provide protection against future open-circuit cell failure. Further testing with switches F01 and F02 may provide clarification. The formation of a continuous low impedance path (a homogeneous low melting point alloy), has been confirmed - which is the expected mode of operation.

Keys, Denney↗
NASA NTRS1993

Technical support for digital systems technology development. Task order 1: ISP contention analysis and control

Alternatives for realizing a packet-based network switch for use on a frequency division multiple access/time division multiplexed (FDMA/TDM) geostationary communication satellite were investigated. Each of the eight downlink beams supports eight directed dwells. The design needed to accommodate multicast packets with very low probability of loss due to contention. Three switch architectures were designed and analyzed. An output-queued, shared bus system yielded a functionally simple system, utilizing a first-in, first-out (FIFO) memory per downlink dwell, but at the expense of a large total memory requirement. A shared memory architecture offered the most efficiency in memory requirements, requiring about half the memory of the shared bus design. The processing requirement for the shared-memory system adds system complexity that may offset the benefits of the smaller memory. An alternative design using a shared memory buffer per downlink beam decreases circuit complexity through a distributed design, and requires at most 1000 packets of memory more than the completely shared memory design. Modifications to the basic packet switch designs were proposed to accommodate circuit-switched traffic, which must be served on a periodic basis with minimal delay. Methods for dynamically controlling the downlink dwell lengths were developed and analyzed. These methods adapt quickly to changing traffic demands, and do not add significant complexity or cost to the satellite and ground station designs. Methods for reducing the memory requirement by not requiring the satellite to store full packets were also proposed and analyzed. In addition, optimal packet and dwell lengths were computed as functions of memory size for the three switch architectures.

Stehle, Roy H.↗
NASA NTRS1966

Instrument automatically selects peak acceleration signal from several accelerometers

Solid state circuit selects the highest of several ac accelerometer signals and gates this signal to an output amplifier, preserving all the frequency information in the peak signal. If the amplitudes of the accelerometer signals change with time, the circuit will continually switch to the highest signal, rejecting the smaller signals.

Chapman, C. P.↗
NASA NTRS1970

Low power NAND gate

Complementary p-n-p transistor, used as the load resistor in an integrated circuit, reduces the switching time and the steady state dc current, and allows for a lower supply voltage. Current limiting is achieved by a novel unity-gain transistor.

Lin, H. C.↗
NASA NTRS1972

Oxygen pressure control for electrolysis cells

Duty cycle of switched, constant current circuit controlled by pressure sensor provides oxygen at a constant pressure from a cell which electrolyzes water, eliminating possibility of cell damage by excessive oxygen demand.

Powell, J. D.↗
NASA NTRS1972

Peak-power-point monitor for solar panel

Attempt was made to determine solar cell panel peak power capability without disrupting power flow from panel. Separate solar cell strings were switched from panel circuits, and increasingly larger loads were added rapidly until peak power points were transversed. String wattage output was recorded and all stored string measurements summed together indicate peak power point in panel.

Schloss, A. I.↗
NASA NTRS1973

Parasitic suppressing circuit

A circuit for suppressing parasitic oscillations across an inductor operating in a resonant mode is described. The circuit includes a switch means and resistive means connected serially across the inductor. A unidirectional resistive-capacitive network is also connected across the inductor and to the switch means to automatically render the switch means conducting when inductive current through the inductor ceases to flow.

Fowler, J. T.↗
NASA NTRS1972

Self-healing fuse development.

The self-healing fuse is a very fast acting current overload protective device which opens and recloses in a few milliseconds. The fuse confines a mercury column in an insulated channel and returns the mercury to the channel after firing. Ratings 5 to 50 A at 600 peak volts are possible with a life of hundreds of cycles. Compared to conventional fuses, much less fault current energy fires the fuse by heating the mercury to boiling temperature. Next an arc discharge develops while explosive forces expel the liquid mercury from the channel. Then the high impedance arc either extinguishes immediately, or operates for a few milliseconds, until a switch opens the circuit.

Jones, N. D.↗
NASA NTRS1974

The problem of controlling the directivity of low directivity antennas on spacecraft in flight

Interests exist in the creation of antennas allowing adjustment of the radiation pattern and directivity in flight without using complex switching and matching circuits. Results are presented of certain experimental tests performed with log-periodic conical helical antennas to determine the possibilities of regulation of their radiation patterns without changing the structure of the current-carrying elements, supply connections, etc.

Mashkov, V. I.↗
NASA NTRS1977

The solid state remote power controller - Its status, use and perspective

Remote power controllers (RPCs) are solid state devices that combine in one unit the capability to perform all the needed functions of load switching, overload protection, and a direct indication of whether the load is on or off. They provide total system protection of equipment and wires. RPCs are designed to be located near the load and communicate control and status information remotely via low level signals of a few milliwatts. The design and operation of the RPC are considered, taking into account the operation of an RPC, the RPC power switch and drive circuits, control and trip circuits, fail-safe devices, and RPC overcurrent protection. Attention is given to the RPC development status, RPC applications, and RPC perspectives.

Sundberg, G. R.↗
NASA NTRS1979

Photographic combustion characterization of LOX/hydrocarbon type propellants

Single element injectors and two fuels were tested with the aim of photographically characterizing observed combustion phenomena. The three injectors tested were the O-F-O triplet, the transverse like on like (TLOL), and the rectangular unlike doublet (RUD). The fuels tested were RP-1 and propane. The hot firings were conducted in a specifically constructed chamber fitted with quartz windows for photographically viewing the impingement spray field. All LOX/HC testing demonstrated coking with the RP-1 fuel leaving far more soot than the propane fuel. No fuel freezing or popping was experienced under the test conditions evaluated. Carbon particle emission and combustion light brilliance increased with Pc for both fuels although RP-1 was far more energetic in this respect. The RSS phenomena appear to be present in the high Pc tests as evidenced by striations in the spray pattern and by separate fuel rich and oxidizer rich areas. The RUD element was also tested as a fuel rich gas generator element by switching the propellant circuits. Excessive sooting occurred at this low mixture ratio (0.55), precluding photographic data.

Judd, D. C.↗
NASA NTRS1984

Using a PFET To Commutate an SCR

Accidental turn-on prevented. PFET diverts load current around SCR to prevent false SCR triggering from current and voltage switching transients. New circuit used in all types of single phase and polyphase inverters and in buck-boost-, and flyback regulators.

Edwards, D. B.↗
NASA NTRS1985

Commutating Permanent-Magnet Motors At Low Speed

Circuit provides forced commutation during starting. Forced commutation circuit diverts current from inverter SCR's and turns SCR's off during commutation intervals. Silicon controlled rectifier in circuit unnecessary when switch S10 replaced by high-current, high-voltage transistor. At present, high-current, low-voltage device must suffice.

Dolland, C.↗