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


Last Updated: December 31, 2017 09:52 AM
Circuits Designed by Dave Johnson, P.E. :
Banister_Illuminated_for_Safety  -  The remote capacitance sensor circuit is placed inside a small potting shell, which contained a three screw terminal block and a single turn variable resistor.  The variable resistor allowed the capacitance needed to activate the switch to be set from about 10pf to 170pF.
 . . . Dave Johnson, Lubbock TX-DC Magazines - 2nd Q 2012

Battery (12v) Load Cutout Circuit -  Lead-acid batteries should not be discharged below a certain point if they are to last.  Also, you don’t want certain 12v powered devices, which might be plugged into a car’s cigarette lighter outlet, to drain the car battery down to a point where the car . . . Hobby Circuit designed by Dave Johnson P.E.-August, 2009

Beeper indicates Check Engine -  When driving down a busy road, you may not notice a “check engine” indicator light that suddenly turns on within the car’s instrument panel.  You could drive for many miles before noticing the light.  To provide an audible indication of trouble, the hobby . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

Check Engine Beeper -  When driving down a busy road, you may not notice a “check engine” indicator light that suddenly turns on within the car’s instrument panel.  You could drive for many miles before noticing the light.  To provide an audible indication of trouble, the hobby . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006

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:

Automatic Power-Off Saves Battery -  12/19/96 EDN Design Ideas:  The Basic training program in Listing 1  helps visually handicapped people easily learn Braille dot code with the help of a trainer.  The trainer generates six-pin Braille code using six solenoids operating on an LPT1/2 either by directly connecting the low-power solenoids to the data bits of the parallel port or by driving solenoid pins (pull-out type] using an UN2003 power driver (Figure 1).  Push-in type solenoids require complemented (0 for 1 and 1 for 0] Braille-code data bits or an extra inverter on the LPT1 port __ Circuit Design by Jose Carlos Cossio, Santander, Spain

Automatic Power-Resumption Alarm -  Most power-resumption alarm devices produce non-stop alarm when power resumes.  To overcome this problem, here is an automatic circuit that sounds an alarm for a few seconds only after power resumes....__ Electronics Projects for You

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

Banister_Illuminated_for_Safety  -  The remote capacitance sensor circuit is placed inside a small potting shell, which contained a three screw terminal block and a single turn variable resistor.  The variable resistor allowed the capacitance needed to activate the switch to be set from about 10pf to 170pF.  . . Dave Johnson, Lubbock TX-DC Magazines - 2nd Q 2012

Battery (12v) Load Cutout Circuit -  Lead-acid batteries should not be discharged below a certain point if they are to last.  Also, you don’t want certain 12v powered devices, which might be plugged into a car’s cigarette lighter outlet, to drain the car battery down to a point where the car . . . Hobby Circuit designed by Dave Johnson P.E.-August, 2009

Battery automatic power-off has simpler Design -  31-Mar-05 EDN Design Ideas:  Simplified circuit provide as timed battery cut-off to save power __ Circuit Design by Yongping Xia, Navcom Technology, Torrance, CA

Battery Discharge Monitor -  Here is a battery monitor circuit which disconnects the load when the battery is discharged, preventing a deep discharge which could cause permanent battery damage.  The battery is automatically reconnected when a battery charger or other DC source is connected across the load.  Select a relay which requires less than 100ma coil current and with contacts capable of handling the load and charging __  Contact:  Charles Wenzel of Wenzel Associates, Inc.

Battery Protection Allows Surges -  06/05/97 EDN Design Ideas:  Circuit monitors two lithium-ion batteries and protects both of m against Overcharging, Overdischarging, and undervoltage __ Circuit Design by Ron Lenk, Temic/Siliconix, Santa Clara, CA

Beeper indicates Check Engine -  When driving down a busy road, you may not notice a “check engine” indicator light that suddenly turns on within the car’s instrument panel.  You could drive for many miles before noticing the light.  To provide an audible indication of trouble, the hobby . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

Bias supply provides short-circuit protection -  09/16/99 EDN Design Ideas:   Most power-supply designs require protection from a short-circuit fault condition.  One of the methods of short-circuit protection is cycling, or the "hiccup-mode" method.  This method is an effective way of controlling a short-circuit fault condition while minimizing power loss in the circuit.  Figure 1 shows a trickle-charged bias supply that uses an LT1431 programmable reference, IC 1, to start an LT1680 high-power dc/dc step-up controller, IC 2, which operates here in a forward-converter topology.    __ Circuit Design by Dave Kim, Linear Technology Corp, Milpitas, CA - September 16, 1999

Blown Fuse Indicator -  This blown fuse indicator will work with a wide range of DC supply voltages from 5V to 50V.  it illuminates LED1 when the fuse blows.  With the fuse intact, Q1 is held off and there is no bias current available for the base of Q2.  So the LED is off.  When the fuse blows, a__ 

Blown Fuse Indicator -  Generally, when an equipment indicates no power, the cause may be just a blown fuse.  Here is a circuit that shows the condition of fuse through LEDs.  This compact circuit is...__ Electronics Projects for You

Blown Fuse Indicator -  a simple way to see if a fuse has blown without removing it from its holder __ Designed by Andy Collison

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

Broken Charger-connection Alert -  Detects if a device is not properly connected to its supply.    Suitable for battery chargers, portable appliance supplies etc.   __ Contact Flavio Dellepiane, fladello @ tin.it

Build a Safety Switch Checker -  Simple unit that lets you check that each power point is covered.  it also verifies the earth connection.__ SiliconChip

Carbon Monoxide Alarm -  Carbon monoxide is an insidious poison which can - and does - kill.  it's colourless, odourless and sneaks up on you!  The first time victims become aware of carbon monoxide poisoning could be too late.__ SiliconChip

Check Engine Beeper -  When driving down a busy road, you may not notice a “check engine” indicator light that suddenly turns on within the car’s instrument panel.  You could drive for many miles before noticing the light.  To provide an audible indication of trouble, the hobby . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006

Circuit Breaker Has Programmable Delay -  01/16/97 EDN Design Ideas:  The circuit in Figure 1 provide as overload and short-circuit protection to a 5V power-supply output.  The heart of the circuit is the LT1620, a charge-current controller designed for high-efficiency, switch-mode battery chargers.  The IC 's versatility allows you to use it as an electronic circuit breaker.  The circuit amplifies the voltage across current-sense resistor __ Circuit Design by David Bell, Linear Technology Corp, Milpitas, CA

Circuit Breaker Provides Overcurrent & Precise Overvoltage Protection -  7-Jun-07 EDN Design Ideas:  A simple circuit breaker delivers precision overvoltage protection and overcurrent protection __ Circuit Design by Anthony H Smith, Scitech, Bedfordshire, England

Circuit Detects & Disconnects Overvoltage -  04/25/96 EDN Design Ideas:  The circuit in Fig.1 protects circuits and systems with power supplies that may exceed safe limits.  One example is small consumer products that use external ac adapters; it's easy to mistakenly plug in the wrong adapter.  Another example is a portable system that uses a rechargeable battery pack.  if the battery pack is absent or fails to open during recharging, a high-compliance charger can deliver excessive voltages to the system __ Circuit Design by Kerry Lacanette, National Semiconductor Corp, Santa Clara, CA

Circuit Ensures Safety In Power-On Operation -  04/24/03 EDN Design Ideas:  Buck converter handles battery-backup system - Computers find universal use in industrial-control systems.  During power- and start-up sequences (booting], the outputs of such control systems may yield uncontrolled pulses before the software defines the correct status.  if these outputs control the power-on state of a system, these uncontrolled pulses could have dramatic consequences __ Circuit Design by Jean-Bernard Guiot, DCS AG, Allschwil, Switzerland

Circuit folds back current during fault conditions -  11/28/02 EDN Design Ideas:  You can use monolithic linear regulators at currents lower than 5A for most applications.  Most manufacturers of these devices integrate current-limiting and thermal shutdown to prevent damage during fault conditions.  For currents greater than 5A, most linear supplies use controllers that allow the user to select the pass element to handle different current requirements __ Circuit Design by Martin Galinski, Micrel Semiconductor, San Jose, CA

Circuit for Measuring 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

Circuit Guards Against Battery Reversal -  07/06/95 EDN Design Ideas:  The circuit in Fig 1 protects a battery-operated system in two ways  Q1 prevents damage from the flow of reverse current that could occur if you install the battery backward, and Q3 prevents the excessive current flow that could occur with a sudden load increase or a short circuit.  A properly installed battery fully enhances Q1 by pulling i __ Circuit Design by Dana Davis, Maxim Integrated Products, Sunnyvale, CA

Circuit guards Amplifier outputs against overvoltage -  07/05/07  EDN Design Ideas:  An automotive-protection circuit withstands repeated insults of direct short circuits to the full battery voltage __ Circuit Design by John Guy, Maxim Integrated Products, Sunnyvale, CA

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

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

Circuit 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

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

Circuit offers series protection against power-line transients -  14-Oct-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 sensitive circuitry against overvoltage is to add parallel clamps.  Fuses or other current-limiting devices precede these clamps' high energy-absorption capability __ Circuit Design by Alfredo Saab and Travis Eichhorn, Maxim Integrated Products, Sunnyvale, CA

Circuit Prevents Deep Discharge Of Batteries -  09/26/96 EDN Design Ideas:  To avoid the deep discharge that can destroy or shorten the life of a rechargeable battery, you must disconnect its load before the discharge is complete __ Circuit Design by Ron Clark and Larry Suppan, Maxim Integrated Products

Circuit prevents processor latch-up -  03/04/99 EDN Design Ideas:  Simple circuit prevents processor latch-up.  Dual one-shot makes rising- and falling-edge detector.  Simple circuit measures diesel's rotations per minute.  Fast, compact routine interfaces EEPROM to µC.  Photodetector sorts objects.  Single-button lock provide as high security.   __ Circuit Design by Michal Kobylecki and Wojda Wlodzimierz, MK Design, Warsaw, Poland

Circuit protects against ac-line disturbances -  07/02/98 EDN Design Ideas:  NOTE:    FILE
has several circuits, please scroll to find this one.  The circuit in Figure 1 protects the ac line against disturbances.  it operates by switching off the power supply upon detection of undervoltage or overvoltage conditions.  The circuit thus protects refrigerators, washing machines, air conditioners, and other appliances from permanent damage that could accrue from working outside their specified power requirements.  The problem assumes particular importance in underdeveloped countries or regions where the ac-supply network is incorrectly configured, and the voltage frequently drops to levels low enough to damage coils and motors.  When the ac-line voltage returns to its nominal level, the circuit automatically resets a switch and reconnects the line voltage.   __ Circuit Design by Basilio Simoes, ISA, Coimbra, Portugal

Circuit protects bus from 5V swings -  14-Nov-02 EDN Design Ideas:  The circuit in Figure 1 automatically detects voltage and protects a bus, such as a 3.3V-limited PCI bus, from 5V signal-level swings.  You can also use the circuit to determine bus-voltage swings within one bus-cycle for setting appropriate termination voltages of protection diodes or termination resistors __ Circuit Design by Said Jackson, Equator Technologies Inc, Campbell, CA

Circuit Protects Computer's Input -  05/26/94 EDN Design Ideas:  The circuit in Fig 1 performs input protection, level translation, isolation, and debouncing.  The circuit allowed the output of a relay driver to connect to a computer even though the relay driver delivered a voltage as high as 24V and the relay driver had no ground connection.  With the values in Fig 1 the low and high thresholds at the circuit's __ Circuit Design by Ang Tzu Seng, Halliburton Drilling Systems, Singapore

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


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