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 Safety / Protection Circuits
Safety / Protection:  # - G        H - Q        R - Z


Last Updated: October 24, 2017 02:55 PM
Circuits Designed by Dave Johnson, P.E. :

Replace a Pushbutton Switch with this Infrared Safety Switch -  Using a slotted optical sensor, this circuit can be used as a replacement for a large mushroom pushbutton safety switch . . . Hobby Circuit designed by David A. Johnson P.E.-July, 2006

Simple Circuit for White LED Night Light -  This simple circuit is designed to plug into a standard AC electrical outlet.  it uses four super bright white light emitting diodes (LED) in conjunction with a capacitor coupled full wave rectifier circuit. . . Circuit by David Johnson P.E.-July, 2003

Capacitance Proximity Switch
Draws very low power - Ideal for battery-powered applications
6 Models Available - Call 806-368-7747


Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

RC-Timed Shutoff Function Uses Op Amp & Momentary Switch -  02/16/12  EDN Design Ideas:  Battery-operated instrument benefited from auto-power shutdown.  A handheld, battery-operated “fiber finder” measures the light escaping from an optical fiber when clamped in a V-shaped block under slight pressure.  A pair of photodiodes on each side of the resulting bend compares analog levels to indicate the presence and direction of light travel, and PLL tone decoders indicate the presence of as many as three optical-modulation tones.  The idea is to “tag” a fiber with a central-office signal __ Circuit Design by Glen Chenier, Teeter Totter Tree Stuff, Allen, TX

Reduce Acoustic Noise From Capacitors -  02/17/11  EDN Design Ideas:  Adding parts or cutting PCB slots can make a difference.  Some surface-mount capacitors exhibit acoustic noise when operated at frequencies in the audio range.  A recent design uses 10-μF, 35V X5R 1206 ceramic capacitors that produce noticeable acoustic noise.  To quiet such a board, you can use acoustically quiet capacitors from manufacturers such as Murata and Kemet.  Unfortunately, they tend to cost more than standard parts.  Another option is to use capacitors with a higher voltage rating __ Circuit Design by Damian Bonicatto, Landis+Gyr, Pequot Lakes, MN

Replace a Pushbutton Switch with this Infrared Safety Switch -  Using a slotted optical sensor, this circuit can be used as a replacement for a large mushroom pushbutton safety switch . . . Hobby Circuit designed by David A. Johnson P.E.-July, 2006

Reverse-Polarity-Protection Has No Voltage Drop -  10/20/11  EDN Design Ideas:  A relay does what semiconductors can’t do. __ Circuit Design by Aruna Rubasinghe

Robust 10MHz reference clock input protection & distributor for RF systems -  07/31/14  LTC Design Notes: Design a protected 10MHz reference input without degrading phase noise. __ Circuit Design by LTC Design Note

Safely Deep-discharges NiCd battery  -  04/29/99  EDN-Design ideas –  NOTE:  Scroll to find this circuit.   Also available at - http://m.eet.com/media/1150682/25098-42999dI     Nickel-cadmium (NIC d) 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.  __ Circuit Design by Jim Hagerman, Science & Technology International, Honolulu, HI

Safely swap SCSI disk drives -  09/30/99 EDN Design Ideas:  When you insert an SCA2 (single-connector attach] drive into a live backplane, the power supply's bypass capacitors in the drive  can draw huge transient.    __ Circuit Design by Ajmal Godil, Linear Technology Corp, Milpitas, CA

Safety Device uses GMR sensor -  10-Jul-03 EDN Design Ideas:  This design idea presents a differential safety device to prevent risks arising from current leakages in household applications.  The proposed circuit uses a new method for differential current sensing (Figure 1).  The method entails the use of Helmholtz coils and a magnetic sensor based on the GMR (giant-magnetoresistive] effect __ Circuit Design by J Pelegri-Sebastia and D Ramirez-Munoz, University of Valencia, Spain

Safety flasher warns of high voltage -  02/17/14 - EDN Design Ideas:  A low power circuit warns the user that high voltage is present - Working on high voltage circuits can be dangerous.  Capacitors can maintain high voltage in a system for a considerable time after power is removed __ Circuit Design by Clive Bolton

Save Property & Life with this -  05/13/10 EDN Design Ideas:  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 __ Circuit Design 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/Analog Devices App Note, Jul 8th 2011

SCR overvoltage crowbar -  an over voltage crowbar protection circuit using a silicon controlled rectifier or SCR __ Designed by Ian Poole

Seatbelt reminder -  No circuit description, schematic only__ CdS Electronic

Secure Bootstrap Operation under Light Load -  05/12/11  EDN Design Ideas:  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 IC 1B 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 __ Circuit Design by Chee H How, Kuala Lumpur, Malaysia

Series protection against power-line transients -  10/14/04  EDN Design Ideas:  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 __ Circuit Design 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...__ Electronics Projects for You

Short Protected Power Supply From PC 12V Supply -  This circuit provides a short circuit protected power supply from PC 12V supply voltage.  This is particularly handy when working with PC interfacing projects.   __ Designed by M Asim Khan asimkhan @ sat.net.pk

Short-Circuit Beeper -  Schematic Only__ 

Short-Circuit Protection for Boost Regulators -  DN154 Design Notes__ Linear Technology/Analog Devices

Shunt regulator provides overvoltage protection -  01/15/98 EDN Design Ideas:  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 technique is noveThis File contains several Design ideas, please scoll to this one[This design idea by ROBERT N BUONO, MAHWAH, NJ] __ Circuit Design by ROBERT N BUONO, MAHWAH, NJ

Simple Circuit Automatic-Shutoff Uses FeW Components -  07/23/12 EDN Design Ideas:  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.   __ Circuit Design by Benabadji Noureddine

Simple Circuit Blown-Fuse Indicator Sounds an Alarm -  10-Jul-08 EDN Design Ideas:  A simple blown-fuse-indicator circuit sounds a buzzer and flashes an LED when a fuse blows __ Circuit Design by Vladimir Oleynik, Moscow, Russia

Simple Circuit Electronic 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 Circuit for White LED Night Light -  This simple circuit is designed to plug into a standard AC electrical outlet.  it uses four super bright white light emitting diodes (LED) in conjunction with a capacitor coupled full wave rectifier circuit. . . Circuit by David Johnson P.E.-July, 2003

Simple Circuit Helps to Protect a Vehicle-Reverse Camera -  10/06/11  EDN Design Ideas:  Add a delay to prevent short power pulses as you shift through reverse.   __ Circuit Design by Aruna Rubasinghe

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

Simple Circuit Night-Light Uses a Photoresistor to Detect Dusk -  12/15/11 - Design ideas - You can adjust this battery-powered circuit for different levels. __ Circuit Design by Chau Tran, Analog Devices, Malden, MA

Simple Circuit Prevents Processor Latch-up -  03/04/99 EDN Design Ideas:  (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 PIC 16C63).  The application accommodates as many as 16 DS1820 sensors in a 100m-long network, dubbed MicroLAN by Dallas.   __ Circuit Design by Michal Koby lecki and Wojda Wlodzimierz, MK Design, Warsaw, Poland

Simple Circuit Reverse-Polarity-Protection Has No Voltage Drop -  10/20/11  EDN Design Ideas:  A relay does what semiconductors can’t do. __ Circuit Design by Aruna Rubasinghe

Simple Circuit Safely Deep-Discharges NiCd Battery -  NIC d batteries possess an undesirable memory effect caused by partial discharges.  The remedy is to do a complete discharge before charging again.  Figure 1 shows a simple circuit which performs this feat.  Although relatively straightforward in concept, the circuit has three redeeming features: 1) it is powered by the battery being discharged.2) After the battery is fully discharged current drain is only about 4 uA, usually well below the self-discharge of a battery alone.3) Near end-of-charge the LED flashes.9publised 04/29/99 EDN-Design idea)  __ Designed by Jim Haggerman, Hagerman Technology LLC

Simple Circuit safely Deep-discharges NiCd battery  -  04/29/99  EDN-Design ideas –  NOTE:  Scroll to find this circuit.   Also available at - http://m.eet.com/media/1150682/25098-42999dI     Nickel-cadmium (NIC d) 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.  __ Circuit Design by Jim Hagerman, Science & Technology International, Honolulu, HI

Single Transistor Provides Short-Circuit Protection -  16-Oct-03 EDN Design Ideas:  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 provide as a direct path from the input to the short circuit through the inductor and the catch diode.  Regardless of current-limit protection in the IC , when a short circuit exists in the load, extremely high cu __ Circuit Design 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...__ Electronics Projects for You

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.  The circuit consists of power supply, ...__ Electronics Projects for You

Smart switch cuts transformer turn-on current -  04/23/98 EDN Design Ideas:  NOTE: File contains multiple circuits scroll to find this circuit.   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 winding __ Circuit Design 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...__ Electronics Projects for You

Smoke Extractor -  Here is a low-cost circuit that automatically extracts solder fumes while you assemble a circuit, thereby saving you from inhaling the same.  The solder paste gives off toxic fumes, which could...__ Electronics Projects for You

SMPS Spark Suppressor -  This circuit protects the power plug of a switched-mode power supply (SMPS) against sparks that may damage its contact terminals.  it normally happens when the device (laptop charger, mobile charger, etc)...__ Electronics Projects for You

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Safety / Protection:  # - G        H - Q        R - Z

 


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