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


Last Updated: October 09, 2017 03:39 PM
Circuits Designed by Dave Johnson, P.E. :

120 VAC Low Voltage Alarm - This circuit will activate a beeper alarm whenever the AC line voltage is less than 100vac.. . . Circuit by David A. Johnson P.E.-July, 2006

12v Battery 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. . . Circuit by David A. Johnson P.E.-August, 2009

18v AC to DC Power Supply - This is a classic linear power supply which produces a regulated 18v, rated at about 1 amp. . . Circuit by David A. Johnson P.E.-July, 2006

1W White LED Night Light - As many of you know, I have a pet peeve with poorly made LED night lights.  Often, the light from the LED quickly fades, so within months, the light is useless.  I have posted several versions of modified night lights using higher quality components.  This circuit is yet another version, which produces much more light than those other designs. . . . Hobby Circuit designed by Dave Johnson P.E.-November, 2008

AC Power Loss Alarm - I’ve been having a problem with my instant hot water system lately.  This system circulates electrically heated water throughout my house using a small pump.  The pump is wired into a ground fault interrupter   (GFI) module.  Every now and then, the GFI trips, leaving me without hot water. . . Circuit by Dave Johnson P.E.-March, 2009

AC to DC 18V Power Supply - This is a classic linear power supply which produces a regulated 18v, rated at about 1 amp . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

Alarm Beeps when the “Check Engine” Light Turns On - When wired into a car’s indicator light panel, this circuit will turn on a loud beeper when the “check engine” light turns on. . . Circuit by David A. 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:

1 Transistor Provides Short-Circuit Protection -  10/16/03  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 th __ Circuit Design by Keith Szolusha, Linear Technology Corp, Milpitas, CA

12 Volt Battery Charge 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.

12 volt battery Monitor -  R1 controls the trip-point of the circuit.  when the voltage falls below the trip-point, the LED lights.  adjust it to the desired level.  to use this circuit to monitor a 6v battery, substitute D1 for a 3.3  volt zener diode and adjust R1 accordingly.   __ Designed by Andy Wilson

120 VAC Low Voltage Alarm -  This circuit will activate a beeper alarm whenever the AC line voltage is less than 100vac.. . . Circuit by David A. Johnson P.E.-July, 2006

12V 15A Low Voltage Disconnect -  The LVD1 kit is used for automatically controlling the power to 12V solar-powered battery-operated electronic devices.  it shuts down power when the battery voltage drops to a selected voltage, protecting the battery from damaging excessive discharge conditions.  Power is either automatically or manually reconnected at a selected voltage when the battery is recharged.  An adjustable low-voltage indicator warns of the impending power outage.  The low-voltage signal is externally available, allowing computers to monitor the condition and perform a graceful shutdown.  The low-voltage signal can also be used for triggering a variety of low-voltage warning systems. 
 __ Designed by Solar Orbit Kit

12v Battery 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. . . Circuit by David A. Johnson P.E.-August, 2009

18v AC to DC Power Supply -  This is a classic linear power supply which produces a regulated 18v, rated at about 1 amp. . . Circuit by David A. Johnson P.E.-July, 2006

1W White LED Night Light -  As many of you know, I have a pet peeve with poorly made LED night lights.  Often, the light from the LED quickly fades, so within months, the light is useless.  I have posted several versions of modified night lights using higher quality components.  This circuit is yet another version, which produces much more light than those other designs. . . . Hobby Circuit designed by Dave Johnson P.E.-November, 2008

2 buttons provide safe start -  07/06/00 EDN Design Ideas:  The circuit in Figure 1 provide as a safety interlock that checks the actuation of two pushbuttons before enabling a relay.  When you push both buttons, the circuit actuates the relay.  At that point, you can release one of the switches without the relay' __ Circuit Design by Vincent Himpe, Alcatel Microelectronics, Desselgem, Belgium

24V Overvoltage Regulator Withstands 150V at VIN -  The LT4356 surge stopper protects loads from high voltage transients.  it regulates the output during an overvoltage event, such as load dump in automobiles, by controlling the gate of an external N-channel MOSFET.  The output is limited to a safe value thereby allowing the loads to continue functioning.  The LT4356 also monitors__ Linear Technology/Analog Devices App Note, Apr 26th 2010

28V Vehicle Application with Reverse Voltage Protection -  The LTC4366 surge stopper protects loads from high voltage transients.  By controlling the gate of an external N-channel MOSFET, the LTC4366 regulates the output during an overvoltage transient.  The load may remain operational while the overvoltage is dropped across the MOSFET.  Placing a resistor in the return line isolates the LTC4366 and allows it to float up with the supply; therefore, the upper limit on the output voltage depends only on the availability of high valued resistors and MOSFET ratings.  __ Linear Technology/Analog Devices App Note, Jan 16th 2012

3-Phase Motor Driver Prevents Stall -  01/05/95 EDN Design Ideas:  The circuit in Fig 1 drives a small 24V, 50-Hz motor at about 30 to 40 Hz for use as a chopper motor.  The best starting speed for the motor is about half the final running speed.  Therefore, the circuit uses an intermediate speed to prevent a stall condition.  The circuit uses IC 1Ato count down two cycles after the selection of the intermediate speed.  IC 1B's Johnson divide-by-three counter and IC 2's gates generate the 1208 phase angle __ Circuit Design by PM Kirkby, Crumpsall Electronics, Surrey, England

4A, 12V Overvoltage Output Regulator -  The LT4356 surge stopper protects loads from high voltage transients.  it regulates the output during an overvoltage event, such as load dump in automobiles, by controlling the gate of an external N-channel MOSFET.  The output is limited to a safe value thereby allowing the loads to continue functioning.  The LT4356 also monitors__ Linear Technology/Analog Devices App Note, Apr 26th 2010

5V System Protected from ± 24V Power Supplies -  The LTC4360 overvoltage protection controller safeguards 2.5V to 5.5V systems from power supply overvoltage.  it is designed for portable devices with multiple power supply options including wall adaptors, car battery adaptors and USB ports.  The LTC4360 controls an external N-channel MOSFET in series with the input power__ Linear Technology/Analog Devices App Note, Apr 26th 2010

5V System Protected from ±24V Power Supplies & Overcurrent -  The LTC4362 monolithic overvoltage/overcurrent protector safeguards 2.5V to 5.5V systems from power supply overvoltage.  it is designed for portable devices with multiple power supply options including wall adaptors, car battery adaptors and USB ports.  The LTC4362 features a soft-shutdown controlled by the ON pin and drives__ Linear Technology/Analog Devices App Note, Jul 8th 2011

5V System Protected from 80V Overvoltage -  The LTC4360 overvoltage protection controller safeguards 2.5V to 5.5V systems from power supply overvoltage.  it is designed for portable devices with multiple power supply options including wall adaptors, car battery adaptors and USB ports.  The LTC4360 controls an external N-channel MOSFET in series with the input power__ Linear Technology/Analog Devices App Note, Apr 26th 2010

5V to 3.3V Regulator with Fail-Safe Switchover -  DN82 Design Notes __ Linear Technology/Analog Devices

AC power line failure/resumption alarm -  This mains indicator sounds an alarm whenever AC mains fails or resumes.  it is very useful in industrial installations, cinema halls, hospitals, etc.   __ Designed by V. David

AC power line 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

AC Power Loss Alarm -  i’ve been having a problem with my instant hot water system lately.  This system circulates electrically heated water throughout my house using a small pump.  The pump is wired into a ground fault interrupter (GFi) module.  Every now and then, the GFI trips, leaving me without hot water. . . Circuit by Dave Johnson P.E.-March, 2009

AC to DC 18V Power Supply -  This is a classic linear power supply which produces a regulated 18v, rated at about 1 amp . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

Accurate Power Supply Sequencing Prevents System Damage -  DN384 Design Notes__ Linear Technology/Analog Devices

Active Reflector for Pedestrian Safety -  Pedestrians crossing roads in badly-lit areas, particularly at night or in the early morning, run a risk of accident.  There are readymade arm bands available that reflect the light of incoming...__ Electronics Projects for You

ADC shuts down analogry -  03/03/94 EDN Design Ideas:  Shutting down circuitry not in use is a common method of saving power in portable and battery-powered equipment.  Although many ADCs have the ability to power down, most other analog components, such as op amps and sensors, do not.  The conventional approach to shutting down analog signal-conditioning circuits is to power them using a voltage regulator that has shutdown capability, and to control this regulator using a dedicated signal line from the microcontroller.  Often, how ever, this additional i/O line isn't available.    __ Circuit Design by Emmy Denton, National Semiconductor, Santa Clara, CA

Add fault protection to a 4- to 20-mA loop supply -  22-Jan-04 EDN Design Ideas:  A 4- to 20-mA current loop consists of a power source and a current-measuring device at the control end and a field transmitter that senses process-variable information, such as temperature or pressure, and converts it to a current (Figure 1).  Most such industrial current loops are powered by 24V dc, but that voltage can range from 12 to 36V __ Circuit Design by Mark Pearson, Maxim Integrated Products, Sunnyvale, CA

Adding Thermal Protection to the DS2784 Stand-Alone Fuel Gauge  -  App Note 4192-- 3/26/2008__ Maxim Integrated

Addressing the Physical Security of Encryption Keys -  App Note 4185-- 2/21/2008 -- (add 5/08) __ Maxim Integrated

Advanced capacitors ensure long-term performance stability -  01/24/13  EDN Design Ideas:  To meet the demanding performance and harsh environmental conditions of automotive applications, component manufacturers have developed professional-grade tantalum capacitors that ensure long-term electrical performance stability.  The professional tantalu __ Circuit Design by Radovan Faltus, AVX Tantalum Division

Advanced Polarity Protection with MOSFETs -  Advanced Power Switching and Polarity Protection for Effects __ Designed by © 1999 R.G. Keen

Alarm Beeps when the “Check Engine” Light Turns On -  When wired into a car’s indicator light panel, this circuit will turn on a loud beeper when the “check engine” light turns on. . . Circuit by David A. Johnson P.E.-July, 2006

Amplifier Thermal Protection -  The thermal protection of amplifiers is always a concern, since overheating is a sure way to reduce the life of semiconductors and other components.    Where you don't want to use a fan (such as in Project 42 - Thermo-Fan for Amplifier Cooling) , then a complete shutdown can be performed.   __ Designed by Rod Elliott  ESP

AN-40-005  Prevention & Control of Electrostatic Discharge ESD -  AN-40-005 App Note__ MiniCircuits.com

AN-60-027  Power Supply Transient Protection for MNA & VNA Amplifiers -  AN-60-027 Application Note__ MiniCircuits.com

Anti-Collision Rear Light -  During poor visibility, i.e., when there is fog, or at dawn or dusk, or when your vehicle gets stalled on a lonely stretch of a highway, this flashing light will provide...__ Electronics Projects for You

Asynchronous Latches Safely -  04/28/94 EDN Design Ideas:  The circuit in Fig 1  is a digital latch that is resettable only after the condition that set the latch clears.  A set input (active low] permanently latches the output (active low].  A reset input (active high] resets the output to a logic high __ Circuit Design by Paul A Kemp, NASA Johnson Space Center, Houston, TX

Audio Amp Output Power Limiter -  if you hire out audio equipment, or just don't want the kids to blow up your speakers when you are not home, this is the project for you.  it is a very simple little project, but will protect the speakers from being overdriven.  Any attempt at overdrive will simply cut the amp gain back - the more overdrive, the more the input signal is reduced.   __ Designed by Rod Elliott  ESP

Audio Level Control Device -  Controlling the level of an audio signal by means of an applied voltage or current has always been problematical but often desirable, particularly when it is necessary to control a circuit from a computer.  This App Note deals with voltage or current controlled attenuators using optocouplers, primarily in relatively static situations (as opposed to the dynamic control that occurs in compressors, limiters and noise gates  __ Designed by Solines, a Cassio Company

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

 


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