Safety / Protection Circuits, Page 9
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Last Updated on: Wednesday, November 29, 2017 05:39 AM

Save Property and Life with this Circuit -  05/13/10 EDN Design Idea   The circuit in Figure 1 sounds an alarm whenever the perimeter- protection line—a thin copper wire of appropriate length—breaks. You can get the thin wire from a used relay coil. Place the wire around a tent, a camping area, or a… [by Vladimir Oleynik, Moscow, Russia]

SCR Crowbar -  The LTC1696 is a standalone power supply overvoltage monitor and protection device designed to protect a power supply load in the event of an overvoltage fault. It monitors two adjustable output voltages. If an overvoltage condition is detected, the output drives either an external SCR crowbar or turns off external back-to-back… [Linear Technology App Note, Jul 8th 2011]

SCR overvoltage crowbar circuit -  an over voltage crowbar protection circuit using a silicon controlled rectifier or SCR… [by Ian Poole]

Seatbelt reminder circuit -  No circuit description, schematic only… [CdS Electronic's website]

Secure Bootstrap Operation under Light Load -  05/12/11  EDN Design Idea   Additional circuit lets a capacitor charge, preventing voltage dips. A previous Design Idea highlights a potential issue of a bootstrap IC under light-load or prechargedload operation (Reference 1). The circuit in Figure 1, with the additional circuit in the green box, fixes the problem of a voltage dip in the bus-voltage signal. The waveforms in Figure 2 demonstrate how this problem takes place in buck converter IC1B when its output voltage, VBUS, dips below the regulation point at a fixed rate under no load. By inspecting the other traces in Figure 2, you can conclude that the dip of VBUS occurs… [by Chee H How, Kuala Lumpur, Malaysia]

Series protection against power-line transients -  10/14/04  EDN Design Idea   Voltage transients on low-voltage power lines can sometimes attain amplitudes many times the nominal voltage level. That behavior often calls for protection against the application of improper power levels. The usual way to protect… [by Alfredo Saab and Travis Eichhorn, Maxim Integrated Products, Sunnyvale, CA]

Shock-Hazard Warning -  Electrical leakage can cause lethal shocks. But such an unfortunate situation can be avoided with this shock-hazard warning system. It uses minimal number of components and does not need any separate power supply. … [© EFY Enterprises Pvt. Ltd. All rights reserved.]

Short circuit protected Power Supply from PC 12V supply -  … [Wichit Sirichote, designer]

Short-Circuit Beeper -  …

Short-Circuit Protection for Boost Regulators -  DN154 Design Notes (Linear Technology)…

Shunt regulator provides overvoltage protection -  01/15/98  EDN Design Idea   The circuit in Figure 1 uses a typical technique for varying the output voltage of a power supply via a programmable control voltage. Although the topology and schematic details of the power supply are not critical, the protection … [by Robert N Buono, Mahwah, NJ]

Simple Automatic-Shutoff Circuit Uses FeW Components -  07/23/12 Edn Design Idea   This auto-shutoff circuit uses a bare minimum of components. You often need to include a timed automatic-turn-off circuit in battery-powered equipment to extend battery life. Previously published Design Ideas for this function all involve many components (references 1 through 7). The circuit in Figure 1 is a simple automatic-shutoff add-on circuit featuring no quiescent current.… [by Benabadji Noureddine]

Simple Circuit Helps to Protect A Vehicle-Reverse Camera -  10/06/11  EDN Design Idea   Add a delay to prevent short power pulses as you shift through reverse.… [by Aruna Rubasinghe]

Simple Circuit Indicates Health of Lithium-Ion Batteries -  05/14/09  EDN Design Idea   A simple inexpensive circuit quickly indicates a battery pack's health… [by Fritz Weld, Friedberg, Germany]

Simple circuit prevents processor latch-up -  03/04/99 EDN Design Idea   (contains several designs, scroll to find this one)   The circuit in Figure 1 uses a Dallas Semiconductor DS1820 one-wire digital thermometer in a multipoint temperature-measurement system. The DS1820 sensor allows distributed temperature measurement and uses only one wire for both data communication and the power supply. You can easily connect the one-wire interface to a µC (in this example, a PIC16C63). The application accommodates as many as 16 DS1820 sensors in a 100m-long network, dubbed MicroLAN by Dallas.… [by Michal Ko[bylecki and Wojda Wlodzimierz, MK Design, Warsaw, Poland]

Simple circuit safely deep-discharges NiCd battery -  04/29/99 EDN Design Idea (contains several designs, scroll to find this one)   Nickel-cadmium (NiCd) batteries can possess an undesirable memory effect due to partial discharges. The remedy is a complete discharge before charging again. Figure 1a shows a simple circuit that performs this feat. … [by Jim Hagerman, Science & Technology International, Honolulu, HI]

Simple Circuit Safely Deep-Discharges NiCd Battery -  Circuit is powered by the battery being discharged, LED flashes near end-of-charge. Ultra-low current drain won't harm battery if left connected.… [Jim Haggerman, Hagerman Technology LLC]

Simple Electronic Circuit Breaker -  This circuit uses the on-resistance of the MOSFET as the current sensor. Reset it by removing the input power or the load. The circuit draws no current unless tripped.… [Designed by Andrew R. Morris]

Simple Night-Light Uses A Photoresistor to Detect Dusk -  11/11/04  EDN Design Idea   If you need to produce extremely fast pulses in response to an input and trigger, such as for sampling applications, the predictably programmable short-time-interval generator has broad uses. The circuit of Figure 1, built around a quad high-speed comparator and a high-speed gate, has settable 0- to 10-nsec output width with 520-psec, 5V transitions. Pulse width varies less than 100 psec with 5V supply variations of 65%. The minimum input-trigger width is 30 nsec, and input-output delay is 18 nsec.… [by Chau Tran, Analog Devices, Malden, MA]

Simple Reverse-Polarity-Protection Circuit Has No Voltage Drop -  10/20/11  EDN Design Idea   A relay does what semiconductors can’t do. Common methods of reverse-voltage protection employ diodes to prevent damage to a circuit. In one approach, a series diode allows current to flow only if the correct polarity is applied (Figure 1). You can also use a diode bridge to rectify the input so that your circuit always receives the correct polarity (Figure 2). The drawback of these approaches is that they waste power in the voltage drop across the diodes. With an input current of 1A, the circuit in Figure 1 wastes 0.7W, and the circuit in Figure 2 wastes 1.4W. This Design Idea suggests a simple method that has no voltage drop or wasted power (Figure 3).… [by Aruna Rubasinghe]

Single Transistor Provides Short-Circuit Protection -  10/16/03  EDN Design Idea   In certain DC/DC-converter applications, on-chip, cycle-by-cycle current limit may be insufficient protection to prevent a failure during a short circuit. A nonsynchronous boost converter provides a direct path from the input to th… [by Keith Szolusha, Linear Technology Corp, Milpitas, CA]

Smart Battery Protector Using a Shunt Regulator -  The life expectancy of a battery dramatically reduces when it is discharged below the minimum recommended battery voltage. You must disconnect the load before discharging is complete. Otherwise, it can damage the battery or shorten its life. … [© EFY Enterprises Pvt. Ltd. All rights reserved.]

Smart Emergency Light -  Now you need not fear dark nights when power breaks down. Here’s a white LED-based emergency light that automatically turns on when mains power supply fails. … [© EFY Enterprises Pvt. Ltd. All rights reserved.]

Smart switch cuts transformer turn-on current -  04/23/98 EDN Design Idea   Transformer-core saturation can cause inexplicable fuse blowing, system crashes, or premature switch and relay failure. When a core saturates, it loses its inductive characteristics; primary windingFile contains multiple circuits… [by Robert Lindsey, Hansvedt EDM, Urbana, IL]

SMF Battery Guard -  The emergency light is an automatic system in which a rechargeable battery-operated light source turns on as soon as the mains power fails. When the mains supply resumes, the lamp turns off. … [© EFY Enterprises Pvt. Ltd. All rights reserved.]

SMPS Spark Suppressor -  This circuit protects the power plug of a switched-mode power supply (SMPS) against sparks that may damage its contact terminals.… [© EFY Enterprises Pvt. Ltd. All rights reserved.]

Solid-State Flasher Has Short-Circuit Protection -  01/16/97 EDN Design Idea    witches an inductive or resistive grounded load using a bootstrapped n-channel power MOSFET and features short-circuit, reverse-polarity, and transient-input-voltage-spike protection, operates from18 to30-Volt DC, and the circui… [by Navdhish Gupta, TDF Corp, Naperville, IL]

Spark Detector Uses Proximity -  11/27/08  EDN Design Idea   Use a Hall-effect sensor to measure engine rpm with a voltmeter… [by Robert Most, Ferris State University, Big Rapids, MI]

Spark gaps Provide ESD Protection -  09/01/97 EDN Design Idea   Using a spark gap fabricated as part of the conductor pattern of a pc board provides significant protection against ESD damage to an interface circuit. Working with inexpensive passive components, spark gaps can protect interface connector pins against repeated 25-kV discharges. And if you position the spark gap under the connector body, no additional pc-board space is necessary.… [by Bill Ehlers, PSC Inc, Eugene, OR]

Speaker Protector -  Please note that the PCB version is different from the circuit shown in this article. It is actually simpler, but achieves the same functions. Full details are available when you purchase the board. The latest boards are Revision-A, and are slightly different from the previous version.… [Rod Elliott (ESP)]

Stabilized Power Supply With Short Circuit Protection -  Here is an efficient 4-stage stabilized power supply unit for testing electronic circuits. It provides well regulated and stabilized output, which is essential for most electronic circuits to give proper results. The circuit provides an audio- visual indication if there is a short circuit in the PCB under test, so the power supply to the circuit ‘under test’ can be cut-off immediately to save the valuable components from damage.…

Standby Power-Loss Preventer -  Electronic devices consume some power even in the standby mode, i.e., when they have been switched off using a remote handset but not the mains power switch.… [© EFY Enterprises Pvt. Ltd. All rights reserved.]

Supply Failure Backup Light -  In the event of a sudden blackout at night, this circuit switches on automatically to provide sufficient light for around 30 seconds (extendible), which is enough to switch on an emergency lamp or light up a candle. … [© EFY Enterprises Pvt. Ltd. All rights reserved.]

Switcher improves overvoltage-protection circuit -  10-Jun-04 EDN Design Idea   Overvoltage-protection circuits often protect electronic devices from power-supply transients, such as a rise from plugging in batteries or an external power adapter. Although these devices traditionally find use as hysteretic swit… [by Jason Rubadue, National Semiconductor, Thornton, CO]

Synchronize asynchronous reset -  01/06/00 EDN Design Idea    Synchronous reset and asynchronous reset are both common reset mechanisms for state machines, and the reset circuit in Figure 1 combines the advantages of each. Synchronous reset has the advantage of synchronization between clock… [by Willy Tjanaka ]

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