Relaxation oscillator

About: Relaxation oscillator is a research topic. Over the lifetime, 1952 publications have been published within this topic receiving 22326 citations.

Coating apparatus control with delay-duration timer having constant current charging circuit and bistable trigger circuit

Abstract: A control system for turning on and off an apparatus which discharges a coating liquid onto objects at a coating station. A sensor positioned adjacent the path of the objects upstream of the coating station initiates an interval timer as an object passes. After a predetermined time delay, the timer turns on a discharge gun positioned at the coating station, to begin to deposit the liquid upon the object. The timer maintains the discharge gun in an actuated condition for a predetermined time duration, and then turns the gun off. The control provides rapid and reliable turn on and turn off of the coating apparatus without false triggering, and provides precise time intervals which are continuously settable over an exceptionally wide range. The control utilizes a rapid reset hold and lock out circuit, SCR switches, unijunction relaxation oscillators having constant current charging circuits, an over voltage output circuit with short circuit protection, and means for programming the operation of plural discharge devices over different time periods.

MEMS Thermal Flow Sensor With Smart Electronic Interface Circuit

Abstract: A smart system for flow measurement is presented, consisting of a micromachined thermal flow sensor combined with a smart front-end electronic interface. The flow sensor is based on a novel thermal transduction method, which combines the hot-film and calorimetric sensing principles. The sensor consists of four germanium thermistors embedded in a thin membrane and connected to form a Wheatstone bridge supplied with a constant DC current. In this configuration, both the bridge unbalance voltage and the voltage at the bridge supply terminals are functions of the flow offering high initial sensitivity, i.e., near zero flow and wide measurement range, respectively. The front-end interface is based on a CMOS relaxation oscillator circuit where the frequency and the duty cycle of a rectangular-wave output signal are related to the bridge unbalance voltage and the voltage at the bridge supply terminals, respectively. Furthermore, the amplitude of the output signal is a linear function of the operating temperature. In this way, a single output signal advantageously carries two pieces of information related to the flow velocity and provides an additional measurement of the sensor operating temperature, which enables the correction of the temperature dependence of the sensor readouts. The system has been experimentally characterized for the measurement of nitrogen gas flow velocity at different sensor temperatures. The initial sensitivities at room temperature result 13.7 kHz/(m/s) and 23.5%/(m/s), in agreement with FEM simulations, for frequency and duty cycle readouts, respectively, with an equivalent velocity resolution of about 0.5 and 1.3 cm/s.

Simple DC-SQUID system based on a frequency modulated relaxation oscillator

Abstract: Nanobridges with hysteretic I-V (current-voltage) characteristics can be operated as relaxation oscillators when connected to an R-L shunt. A DC SQUID (superconducting quantum interference device) configuration results if two such oscillators are incorporated in a superconducting ring. Operating such a self-oscillating SQUID (SOS) with a suitable bias current leads to an output signal of the order of 10 mV, whose frequency depends on the magnetic flux through the SQUID ring modulo Phi /sub 0/. Due to this large output voltage, no impedance matching or special low-noise preamplifier is needed for the readout scheme. Standard integrated circuits for FM (frequency modulated) signal processing can be used, leading to matchbox-size electronics. Such DC SQUIDs have been made of thin Nb, NbN, and Nb/sub 3/Ge films. The highest sensitivity achieved so far is Nb devices with a white flux noise below 10/sup -5/ Phi /sub 0// square root Hz at 4.2 K. >

Regulated dc-to-dc converter for voltage step-up or step-down with input-output isolation

Abstract: A closed-loop regulated dc-to-dc converter employing an unregulated two-winding inductive-energy storage converter is provided by using a magnetically coupled multivibrator acting as a duty-cycle generator to drive the converter. The multivibrator is comprised of two transistor switches and a saturable transformer. The output of the converter is compared with a reference in a comparator which transmits a binary zero until the output exceeds the reference. When the output exceeds the reference, the binary output of the comparator drives transistor switches, via a dc isolation circuit, which control the multivibrator to turn the multivibrator off. The multivibrator is unbalanced so that a predetermined transistor will always turn on first when the binary feedback signal becomes zero.