LED-Current Limiter Accepts AC or Dc -  07/14/11  EDN-Design Ideas Prevent excessive current from overdriving your LEDs.  LED drivers have lots of features and require plenty of external components.  When your application requires no PWM  (pulse-width-modulated) dimming or controlled frequency operation, your primary concern may be that too much current could damage or destroy your LEDs.  In this case, you can make a simple LED-current limiter from a common low-dropout linear regulator.  The circuit in Figure 1 is an LED light bulb for a landscape-lighting system.  Landscape lighting typically operates from 12V ac, and peak voltage is approximately 17V.  Because the regulator is in series with the LED string, the LED-string current equals the regulator’s output current.   Design by Roger Griswold

Limits DV/DTand Capacitor inrush at Regulator Turn On -  10/11/07 EDN-Design Ideas Adding a simple circuit to the adjust pin of a regulator controls the dV/dt of the output voltage, limiting inrush current Design by W Stephen Woodward, Chapel Hill, NC

Over / Under-Voltage Protection Of Electrical Appliances -  This circuit protects refrigerators as well as other appliances from over and under-voltage.  Operational amplifier IC LM324  (IC2) is used here as a comparator. IC LM324 consists of four operational amplifiers,...__ Electronics Projects for You

Over Voltage Protection for LM317 -  It is a voltage regulator that allows a 6v portable supply to be derived from the 12v car battery.  You can add a 6.2V zener diode and a LED to warn you when the input supply is overvoltage.  If you could find a relay that would operate from 6.2v right up to 12v that you could connect in such a way that if over voltage occurred,  __ Designed by submitted Adam

Overvoltage Regulator with 250V Surge Protection -  The LT4363 surge stopper protects loads from high voltage transients.  It regulates the output during an overvoltage event, such as load dump in vehicles, by controlling the gate of an external N-channel MOSFET.  The output is limited to a safe value allowing the loads to continue functioning.  The LT4363 also monitors the voltage__ Linear Technology/Analog Devices App Note, Jan 16th 2012

Overvoltage Regulator with Low Battery Detection & Output Keep Alive During Shutdown -  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

Passive limits inrush current -  09/26/02 EDN-Design Ideas You would normally limit the inrush current during start-up of a rectifier circuit with a capacitor output filter by using the circuit in Figure 1.  You insert a high resistance in series with the ac input or the dc output of the rectifier and then short-circuit the resistance with a switch once the filter capacitor is sufficiently charged Design by Sunil Tiwari and Mangesh Borage, Centre for Advanced Technology, Indore, India

Pira CZ Stereo Encoder for FM Broadcasting -  This stereo encoder is a halfway between analogue and digital processing.  It combines the best from both domains to provide high-quality and easy to build device.  The sampling frequency used in this stereo encoder is 97 times __ Jan Kolar

Protection from Overvoltage & Overcurrent -  The LTC4361 overvoltage/overcurrent protection controller safeguards 2.5V to 5.5V systems from input supply overvoltage.  It is designed for portable devices with multiple power supply options including wall adaptors, car battery adaptors and USB ports.  The LTC4361 controls an external N-channel MOSFET in series with the__ Linear Technology/Analog Devices App Note, Apr 26th 2010

Protection of USB Port from Overvoltage & 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.  __ Linear Technology/Analog Devices App Note, Jul 8th 2011

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

Series lamp limiter -  The idea behind this project is not new.  Engineers and enthusiasts have used it for yearsso it is well proven.  It is also very simpleconnect a 100W lamp bulb in series with the supply to the set.  At 230V, a 100W lamp requires about 400mA to illuminate fully.  Therefore, the maximum current that can flow through your faulty set is 400mA.  At this current, virtually all the voltage is dropped across the lamp, not across the set __ Designed by Paul Stenning

Simple Circuit & effective inrush current limiter stops surges -  08/02/07 EDN-Design Ideas Active circuit and relay replace lossy negative-temperature-coefficient thermistor.  Offline power supplies that drive loads of 200W and more require inrush-current limiters.  Unrestricted inrush currents can reach hundreds of amperes, which may damage the line rectifier, open the fuse and input-filter inductors, and damage the PFC  (power-factor-correction) filter capacitors.  A simple method of limiting the inrush current uses an NTC  (negative-thermal-coefficient) thermistor that connects in series with the supply line.   Design by Gregory Mirsky

Simple Circuit & effective inrush-current limiter stops surges -  08/04/07 EDN-Design Ideas Active circuit and relay replace lossy negative-temperature-coefficient thermistor Design by Gregory Mirsky, Juno Lighting Group, ModuLight Division, Des Plaines, I - L

Simple Circuit current limiting for LED flashlights -  I have modified my 3-White LED 3-AA cell flashlight by adding filament bulbs in series with the LED's to form a "ballast" utilizing the positive resistance-vs-temp characteristic of tungsten as a simple current source.  I did this to increase the battery life  (at the expense of initial brightness) , and to increase the lifetime of the LED's.  The flashlight, which was given to me, appears to be an early C. Crane unit. As in most of these simple lights, the 3 LED's are wired in parallel on a tiny circular PC board and connected directly to the 3 AA Alkaline cells.

Soft limiter for oscillators uses emitter-degenerated differential pair -  10/12/06 EDN-Design Ideas Phase-shift network plus a few active components yields low-distortion outputMost oscillator circuits include a nonlinear amplitude control that sustains oscillations at a desired amplitude with minimum output distortion.  One approach uses the output sinusoid's amplitude to control a circuit element's resistance, such as that of a JFET operating in its triode-characteristics region.  Another control method uses a limiter circuit that allows oscillations Design by Douglas Sudjian, Resonext Communications Inc, San Jose, CA

Soft Start -  The circuit will limit the current through the supply wires to 5.5A for about 1.5sec.  After that time the relay will close and the current flow won't be restricted anymore.  This is a very interesting circuit if you have a large toroid with big electrolytic caps connected to the power supply, since these will act like short circuits for a small amount of time if they start charging.  

Soft-limiter forms basis of Simple Circuit AM Modulator -  09/03/07  EDN-Design Ideas Inserting diodes biased by reference voltages in the feedback loop of an op amp yields a soft limiter that you can use as the basis of an AM modulator Design by Herminio Martínez, Encarna García, and Juan Gámiz, Technical University of Catalonia, Barcelona, Spain

Stereo Broadcast Limiter -  Circuit for the Ramsey FM10a/FM25 Transmitter __ Designed by G. Forrest Cook

Stereo Limiter -  Stereo Broadcast Limiter Circuit for Ramsey.  

Supercapacitor Voltage Limiting Circuit -  Supercapacitors are working their way into more and more applications where electrical energy needs to be stored.  These robust devices can be charged and discharged 1000s of times and will typically outlast a battery. . . Circuit by David Johnson P.E.-March, 2010

Thermocouple Temperature Activates Relay -  Voltage from a high temperature thermocouple activates a relay when the sensor detects a temperature above 1000 degrees F. . . Circuit by Dave Johnson P.E.-July, 2006

Three Fake Alarms -  Battery Powered LED Circuits:  Flashing LEDs can be used to create the impression that an alarm has been fitted.  Or they can be used in conjunction with a real alarmto warn-off a potential thief.  These three small circuits will flash anything from a single LEDup to 90 LEDs and beyondwith a variety of speeds and patterns.  __ Designed by Ron J.

Ultrasound Receiver-40Khz -  A X100 transistor amplifier is followed by a zero cross detector circuit, using a voltage comparator.  The output is a TTL logic signal, corresponding to the received 40KHz signal . . . Hobby Circuit designed by David A. Johnson P.E.-January, 2006

Voltage Limiter Generates Supplies that Improve Standard Diode Technique -  Some systems require a voltage limiter to protect the input circuit.  Designers can connect diodes to V CC and Gnd to create a simple solution  (Fig.1) .  This simplicity, however, comes at a __ Designed by Electronic Design Europe 10.02.11 Yossi Barkan

Voltage Limiting with a Supercapacitor -  Supercapacitors are working their way into more and more applications where electrical energy needs to be stored.  These robust devices can be charged and discharged 1000s of times and will typically outlast a battery . . . Hobby Circuit designed by Dave Johnson P.E.-March, 2010

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