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Sensors and Transducers
Published in Trevor Linsley, Electronic Servicing and Repairs, 2014
The measurement of liquid level in a container is an important measurement in industry and is often used in the chemical mixing process. The simplest and most frequently used level sensor is the simple float switch. A float, moving in response to the liquid's surface, operates a switch to indicate that the liquid has reached a predetermined level. The float of a modern float switch contains a small magnet which acts upon a magnetic reed switch.Fig 12.24 shows a typical float switch. The float, which looks like a cotton bobbin, rises up the central cylinder in response to the liquid level and activates a reed switch contained in the central cylinder. The reed switch is hermetically sealed and can, therefore, operate millions of times without failure because the contacts are not exposed to atmospheric dust and corrosive fumes. The float switch shown is designed for mounting in the top of a container, but side- and bottom-mounted switches are also availabel. They are easily installed, reliable and require virtually no maintenance, which is an important consideration in industry.
Problems with International Standards
Published in Vladimir Gurevich, Digital Protective Relays, 2017
The definition for the term reed switch (p. 3.1.3 of IEC 62246-1) is that it is an “assembly containing contact blades, partly or completely made of magnetic material, hermetically sealed in an envelope.” But, first, all these attributes characterize reed switches of any type, not just dry ones. For example, all these attributes are found in mercury-wetted reed switches. Second, use of the term blade, strictly speaking, describes only certain contact profiles and does not reflect the complete variety of existing reed switches, among which there are also ball and membrane, plunger type, and the like.1
Interfacing
Published in Mike Tooley, PC Based Instrumentation and Control, 2013
Reed switches use an encapsulated reed switch that operates when in the proximity of a permanent magnetic field produced by an actuator magnet. Reed switches are generally available as either normally open (NO) or changeover types. The later may, of course, be readily configured for either NO or NC operation. Distances for successful operation (pull-in) of a reed switch are generally within 8–15 mm (measured between opposite surfaces of the actuator magnet and reed switch assembly). The release range, on the other hand, is generally between 10 and 20 mm.
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