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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. :
Infrared Safety Switch -  Using a slotted optical sensor, this circuit can be used as a replacement for a large mushroom pushbutton safety switch. . . Circuit by Dave Johnson P.E.-July, 2006

Low Voltage 120vAC Power Line Alarm -  This circuit will turn on a beeper when the line voltage drops below 100 volt AC.. . . Circuit by Dave Johnson P.E.-July, 2006

Modified LED Night Light -  I bought some night lights a few months ago from Walmart here in Denver.  The devices were made by Elumina Lighting Technologies inc. (www.  eluminalighting.  com) , their model LED-6200A.  I think I paid about $15 for a pack of three lights.  I wanted a light . . . Hobby Circuit designed by David A. Johnson P.E.-May, 2007

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

Headlight guard -  We can text the functionality of the unit with the vehicle's battery.   The 0V wire connects to the negative terminal of the battery.  The parking light wire connects to the positive terminal.   When these two connections are made, the buzzer will sound.   When we connect the ignition wire to the positive terminal (along with the Parking Light Wire) the buzzer stops.   Every time the ignition wite is removed from the battery, the buzzer will sound.  __ CdS Electronic

Help 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

High-side driver has fault protection -  09/05/02 EDN Design Ideas:  High-side drivers find common use in driving grounded solenoid coils and other loads.  Short-circuit protection for such drivers is essential for avoiding damage from wiring faults and other causes.  Polymer fuses are generally too slow, and discrete current-limiting circuits are large and cumbersome.  The circuit in Figure 1 uses a small, low-dropout linear regulator as a high-side switch and p __ Circuit Design by Carl Spearow, Tokyo Electron, Gilbert, AZ

High-Voltage Breaker Protects to 26V -  09/11/98 EDN Design Ideas:  (PDF link is no longer online) Wide use of the Universal Serial Bus (USB] has LED to a selection of overcurrent-protection circuits for supply rails of 2.7 to 5.5V, but few products are available for voltages higher than that range.  The circuit breaker.    __ Circuit Design  Ted Salazar, Maxim Integrated Products, Sunnyvale, CA

House Security System -  Here is a low-cost, invisible laser circuit to protect your house from thieves or trespassers.  A laser pointer torch, which is easily available in the market, can be used to operate...__ Electronics Projects for You

IC Controlled Emergency Light with Charger -  White LEDs are replacing the conventional incandescent and fluorescent bulbs due to their high power efficiency and low operating voltage.  These can be utilised optimally for emergency lamp and vehicle turning...__ Electronics Projects for You

Impedance transformer flags failed fuse -  17-Dec-04 EDN Design Ideas:  Figure 1depicts a circuit that detects the opening of a miniature circuit breaker or high-rupture-capability fuse in a high-reliability telecommunications power supply.  The circuit generates an alarm when a failure changes the impedance of an electromagnetic sensor.  Traditional fault-detection circuits sense the voltage difference developed across an open fuse, leakage current flowing through __ Circuit Design by Kevin Ackerley, Future Electronics, Vancouver, BC, Canada

Improved Laser-Diode-Clamp Protects Against Overvoltages -  05/29/08  EDN Design Ideas:  Adding a bipolar transistor to a JFET laser-diode clamp protects high-current laser diodes __ Circuit Design by James Zannis, Baulne-en-Brie, France

Increase your driving safety with Quick Brake -  Simple project turns your brake lights on faster than you could ever apply them, to reduce rear-end shunts.__ SiliconChip

Indicate AC-Mains-Fuse Failure -  01/08/09  EDN Design Ideas:  Use this circuit to alert you when a fuse fails __ Circuit Design by Vladimir Oleynik, Moscow, Russia

Indicate 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

Inexpensive self-resetting breaker requires few parts -  01/22/09  EDN Design Ideas:  The circuit breaker pulses power through a pass transistor when the current gets too high, thus protecting the part from excessive heat __ Circuit Design by Anthony H Smith, Scitech, Bedfordshire, England

Infrared Safety Switch -  Using a slotted optical sensor, this circuit can be used as a replacement for a large mushroom pushbutton safety switch. . . Circuit by Dave Johnson P.E.-July, 2006

Input-protection scheme tops other approaches -  01/06/00 EDN Design Ideas:  You typically accomplish overvoltage or surge protection at circuit inputs by connecting diodes to the supply rails, connecting zener diodes to ground, or connecting transzorbs to ground.    __ Circuit Design by Kannan Natarajan, Mediatronix Private Limited, Kerala, India

Inrush limiter also provides short-circuit protection -  06/09/05  EDN Design Ideas:  MOSFET keeps inrush currents due to capacitive loads under control __ Circuit Design by Ryan Brownlee, Process Automation Division, Pepperl & Fuchs Inc, Twinsburg, OH

Inverted Regulator Increases Choice & Reduces Complexity -  112/05/09 EDN Design Ideas:  A simple approach for any high side overcurrent-protection circuit references the entire circuit to the high-side rail __ Circuit Design by David McCracken, Aptos, CA

Isolated Driver Forms Solid-state Breaker -  03/02/98 EDN Design Ideas:  (File contains many circuits, please scroll to find this one) This circuit allows standard TTL logic levels to safely drive a high-power dc load, circuit provide as also overcurrent circuit breaker functionality.    __ Circuit Design by Bobatson, Corley Manufacturing Co, Chattanooga, TN

Load switch with self-resetting breaker -  EDN Design Ideas:  10/20/2014     Protect both load and driver with this elegant little Design ideas __ Circuit Design by Anthony Smith

Logic PSU with OverVoltage Protection -  A simple 5 Volt regulated PSU featuring overvoltage protection. __ Designed by Andy Collison

Loud Speaker Protection & Muting -  Protect speakers from turn-on and turn-off transients and amplifier faults    __ Designed by Rod Elliott  ESP

Low Voltage 120vAC Power Line Alarm -  This circuit will turn on a beeper when the line voltage drops below 100 volt AC.. . . Circuit by Dave Johnson P.E.-July, 2006

Low-error platinum RTD has shutdown capability -  09/14/00 EDN Design Ideas:  Resistor-temperature detectors (RTDs) , are the most stable and popular temperature sensors.  Platinum RTDs allow for a much wider range of temperatures than silicon-based sensors.  in many cases, platinum RTDs sit far from the measurement circuitry, which adds a great deal of error into the measurement system.  The circuit in __ Circuit Design by Reza Moghimi, Analog Devices, Santa Clara, CA

LTC Design Note: 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 Michel Azarian

Mains Supply Failure Alarm -  When ever AC mains supply fails, this circuit alerts you by sounding an alarm.  it also provides a backup light to help you find your way to the torch or the...__ Electronics Projects for You

Mains 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.   __ Designed by Arthur Louis

Make a Simple Circuit PC-Based frequency meter  -  04/29/99  EDN-Design ideas –  NOTE:  Scroll to find this circuit.   A simple, low cost, and precision frequency meter uses only two pins of a pc parallel port (Figure 1). The TTL-level periodic input signal with frequency fiN connects to the ACK pin of LPT1. __ Circuit Design by Radovan Stojanovic, University of Patras, Patras, Greece

May Save Property & Life -  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

Measure Motor Speed Uses Low-Cost Components -  11/08/07  EDN Design Ideas:  A microcontroller-based circuit provide as both an LCD readout and an analog motor-speed output __ Circuit Design by R García-Gil, J Castelló, and JM Espí, Escola Tècnica Superior d’Enginyeria, University of Valencia, Spain

MEET BLINKER-blinking LED's -  Our BLiNKER has many applications; fill your party with blinking BLiNKERS.  Mount the BLiNKER on your bicycle so you'll be more visible and have a safer ride.  Mount it on the car dashboard as an alarm flashing light imitator.  Or mount it on your room door (i.  e.  please do not disturb).  Place BLiNKER anywhere you’d like to draw attention and a smile.  The unique small design will allow you to mount it almost anywhere.  Operate it with 9V battery 12V car battery, via two 1.5V batteries, or via one of our battery simulator kits.   __ Contact Kit from Elich Industrial Development, Corp

Method offers fail-safe variable-reluctance sensors -  11/22/01 EDN Design Ideas:  Variable-reluctance sensors are preferred for industrial and automotive environments, because they sustain mechanical vibration and operation to 300°C.  in most applications, they sense a steel target that is part of a rotating assembly.  Because the unprocessed signal amplitude is proportional to target speed, a sensor whose signal-processing circuitry is designed for high speed cease __ Circuit Design by Phil Levya, Maxim Integrated Products, Sunnyvale, CA

Method provides automatic machine shutdown -  27-May-04 EDN Design Ideas:  Some machines need to run for long periods and therefore may finish their work in the middle of the night or during the weekend.  For the time remaining, until the operator returns, the machines stay idle, uselessly consuming power.  This design idea allows a machine to completely shut itself down after finishing its work __ Circuit Design by Jean-Bernard Guiot, Mulhouse, France

Method provides overpower protection for quasiresonant supplies -  28-Oct-04 EDN Design Ideas:  The main characteristic of quasiresonant switch-mode power supplies is that they exhibit a varying frequency when the input voltage changes.  For a flyback power supply, the power delivered to the output obeys the following equation  POUT=1/2 (LP×iP 2×FSWη], where LP is the primary inductance, IP is the peak primary current, FSW is the switching frequency, and η is the e __ Circuit Design by Nicolas Cyr, On Semiconductor, Toulouse, France

Microcontroller protects DC-motor -  02/17/05  EDN Design Ideas:  Although any overloaded dc motor can draw excessive current and sustain damage, a cooling fan's motor is particularly vulnerable due to fouling by dust, insects, or misplaced objects.  A few fans include built-in overload protection __ Circuit Design by Abel Raynus, Armatron International Inc, Malden, MA

Modified LED Night Light -  I bought some night lights a few months ago from Walmart here in Denver.  The devices were made by Elumina Lighting Technologies inc. (www.  eluminalighting.  com) , their model LED-6200A.  I think I paid about $15 for a pack of three lights.  I wanted a light . . . Hobby Circuit designed by David A. Johnson P.E.-May, 2007

Monitor & Protect Automotive Systems with Integrated Current Sensing -  DN374 Design Notes__ Linear Technology/Analog Devices

Monitors Board, Air & Cpu Temperature to Protect System from Overheating -  App Note 941: IC __ 

MOSFET Beats Murphy's Law -  12/22/94 EDN Design Ideas:  Consider it Murphy's Law: You buy two 15V supplies or one ±15V dual supply to power some op amps.  Then, when the last QA inspector or first customer flips the switch, the power supply hangs up.  This hang-up occurs because the positive supply yanks its output to positive.  The negative supply reads this output as a reverse polarity before it has a chance to start up.  So, the supply's negative regulator gives up.   __ Circuit Design by Phil Harvey, Technology Integration Inc, Bedford, MA

Motor uses Simple Circuit reverse-battery protection -  18-Mar-04 EDN Design Ideas:  This design idea presents a low-side, reverse-battery-protection technique for a dc-motor system.  The system in Figure 1 incorporates two protection options.  The common practice of using a diode for reverse-battery protection does not work with dc motors' inductive loads.  in Figure 1, an Allegro (www. Allegromicro.com) A3940, a low-cost power MOSFET controller, drives a dc motor.  An H-bridge for driving the motor comprises the n-channel MOSFETs Q0 to Q3.  To change the motor's direction from forward (current flowing from Phase A to Phase B) to reverse, the direction of current in the motor winding must reverse.    __ Circuit Design by Dongjie Cheng, Allegro Microsystems, Warminster, PA

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

 


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