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Published in James D. Taylor, Introduction to Ultra-Wideband Radar Systems, 2020
David Platts, Oved S. F. Zucker, Iain A. McIntyre
The subject of magnetic switching is often mentioned in pulsed power work. This is actually a pulse- sharpening technique that is used with another type of primary switch. The operation of a magnetic switch depends on a magnetic material with a very sharp saturation curve. The Metglas materials from Allied make good cores for magnetic switches.14 These materials are thin ribbons of amorphous material made by rapidly quenching the molten metal on a rotating drum. The ribbon is then insulated and wound into a core, as is done to manufacture a conventional tape-wound core. When an inductor that has been wound on a core of this material is subjected to a slowly rising voltage pulse, it initially acts as a high inductance until the core saturates. When the core saturates, the inductance drops to a much smaller value and the current in the circuit rises much more rapidly than it would have without the magnetic switching inductor. Magnetic switches can be used in a multistage configuration to obtain faster risetimes and different output impedances than can be obtained with a single stage. The risetime of a magnetic switch is limited by the material that is used for the core. The flux must be able to diffuse into the material on a time scale shorter than the risetime of the applied pulse. The magnetic switch makes it easier to design the primary switch, and the magnetic switch requires no maintenance. As magnetic switches become more widely known, they probably will be used in many pulse-sharpening applications.
Hardware Components for Automation and Process Control
Published in Stamatios Manesis, George Nikolakopoulos, Introduction to Industrial Automation, 2018
Stamatios Manesis, George Nikolakopoulos
Float level switches: The simplest level switches from a construction point of view are the float-based level switches. In Figure 2.44 some basic types of float switches are shown. The float switch shown in Figure 2.44a requires sidewall mounting, while a similar one shown in Figure 2.44b is suitable for a vertical placement. Both types use a sealed-in-glass magnetic switch (called “reed relay”, which is presented in Section 2.3.4) and a floating part that contains a permanent magnet. When the liquid level is low, the permanent magnet is far from the magnetic switch, and thus its SPST contact is open. When the liquid level increases, the floating magnet is moved toward the magnetic switch. Once the magnetic switch is reached, the floating magnet activates the SPST contact, which subsequently closes. Therefore, the floating magnet follows the changes of the liquid level, and at a designated height, the contact output changes status and remains there as long as the level height does not change.
New Power Semiconductor Devices for Generation of Nano- and Subnanosecond Pulses
Published in James D. Taylor, Ultra-wideband Radar Technology, 2018
3. After closing of the first switch, the sharp voltage pulse appears at the second switch S2 as shown in Figure 9.8. The last feature can lead to the stray dU/dt turning on S2, if S2 is a thyristor. But if S2 is a magnetic switch, the voltage may be used to turn it on.4 Features (1) and (2) are disadvantages in the case of a high-current, high-energy pulse generation, compared with the parallel LC circuits. A piece of transmission line (coaxial cable) may be connected instead of inductor L2. In this case, a rectangular pulse will be generated, and pulse length equals doubled wave propagation time along the line.
Design and evaluation of the Afari: a three-wheeled mobility and balance support device for outdoor exercise
Published in Assistive Technology, 2021
Mohsen Alizadeh Noghani, Drew Browning, Vincent Caccese, Elizabeth DePoy, Stephen Gilson, Ryan Beaumont, Babak Hejrati
To choose an appropriate distance measurement method, two systems were tested on the Afari for comparison. A magnetic switch was used to measure the traveled distance by counting each time a magnet passed the switch, as explained previously. For this experiment, nine magnets were placed evenly on the left wheel’s spokes. The other method was based on using the rotation speed of the wheel, for which we used an Xsens DOT IMU (Xsens Technologies B.V., Enschede, The Netherlands). The IMU was attached to the inside of the 3D-printed enclosure on the wheel shown in Figure 5a. To test the accuracy of the distance measurement methods, a participant used the Afari to traverse the distance between landmarks on the ground that were 10 ft (3.048 m) apart at a comfortable walking speed. During the experiment, four distances of 10, 20, 40, and 80 ft (3.048 m, 6.096 m, 12.192 m, and 24.384 m) were measured by the wheel IMU and the magnetic switch, where each distance was repeated five times. The traveled distance was calculated using the wheel IMU by obtaining the linear velocity of the center of the wheel by multiplying its angular velocity and radius, and then integrating the velocity between the start and stop of its rotation.
Implementation of a Distributed Home Automation Scheme with Custom Hardware Nodes Using ZigBee and MQTT Protocols
Published in IETE Journal of Research, 2021
A. Radhanand, K. N. B. Kumar, Swetha Namburu, P. Sampathkrishna Reddy
ATmega328 with the Arduino bootloader is the microcontroller used in the board shown in Figure 4. MAX 756, a step-up DC-DC converter is used to provide a 5 V supply to the microcontroller. The input voltage to the MAX 756 is provided by two AA batteries. XBee is used for ZigBee communication and its 3.3 V supply voltage is provided by the LM1117 LDO regulator. A magnetic switch is used to detect the opening of the window. The switch consists of two parts a magnet and a reed switch which closes in the proximity of the magnet. The magnet is fixed to the sliding part of the window and the other part is fixed to the window frame. The Normally Open contact closes when the window is closed and opens when the window is opened. A periodic message is sent with the switch status on the ZigBee network [15]. The XBee on the board is configured as a router and forms part of the ZigBee network
First principles investigation of the spin transport properties in graphene-porphine-graphene nanojunctions
Published in Molecular Physics, 2020
In the past decades, magnetic tunnel junction (MTJ) has attracted great interest due to its applications in different fields, such as magnetic switch, magnetic sensors and magnetic random-access memory and so on [1]. The traditional MTJs are constructed by two ferromagnetic (FM) layers and a barrier layer(I). The tunnelling magnetoresistance (TMR) effect is one of the most important characteristics of MTJ [2]. And as high as 604% TMR value has been obtained under room temperature in this kind of MTJ [3]. Recently, the molecular magnetic tunnel junctions (MMTJs) have been considered as a promising spintronic device because of the quantum transport properties can be modified in this kind of MMTJs [4–6]. Especially, the molecular spintronics at the organic single-molecule level obtained much attention [7, 8]. The MMTJs are famous for its series particular spin-related properties, such as negative differential resistance (NDR) [9–11], spin-valve [12], spin-filtering [13–15], rectification [16] and TMR [17].