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Indicator Circuits
Indicators:  #'s - A       B - C       D - F       G - I       J - L       M - P        R - S       T - Z
Last Updated on: Tuesday, October 24, 2017 02:55 PM


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

Circuits Designed by Dave Johnson, P.E. :

High DC Current IndicatorA while back, someone requested a simple method to indicate when 20 to 50 amps of DC current was flowing through a wire.  The circuit below works well and is about as simple as you can get.  A sensitive reed relay . . . Hobby Circuit designed by David Johnson P.E.-April, 2005

High Intensity Line Powered LED FlasherThere are times when you would like to generate an intensely bright flash of light using electrical power from the AC line.  The circuit below can drive a one to three watt power LED with about 350ma of peak current.  Since the circuit drives the LED with. . . Circuit by David Johnson P.E.-December, 2008

Hot AC Power Line IndicatorThe circuit below is designed to detect when a power cable is active (hot) .  When the flat sensor end of the device is held near an active AC line, the bright green LED on the top of the housing will glow.  It is powered by a 3v CR2032 lithium coin cell.  I . . . Hobby Circuit designed by Dave Johnson P.E.-May, 2005

Indicate DC Current FlowThe circuit below is a simple way to indicate when DC current is flowing through a wire.  The circuit is designed so it will turn on a LED indicator light, whenever the voltage drop across a shunt resistor exceeds about 0.1volts.  The value of the resist . . . Hobby Circuit designed by Dave Johnson P.E.-October, 2005

Indicates 120 VAC or 240 VA - CTwo LEDs indicate if a power line has 120vac or 240vac voltage on it . . . Hobby Circuit designed by David A. Johnson P.E.-January, 2007

Indicates Automotive Electrical VoltageWhen troubleshooting the 12v electrical system of an automobile, it is nice to have a simple voltage indicator tool instead of a voltmeter.  This electronic circuit, hobby circuit is powered by two AA or even two N cells, which will provide enough energy . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

Indicates Battery Charge CurrentThis circuit turns on a LED whenever it detects at least 25ma of battery charge current . . . Hobby Circuit designed by David A. Johnson P.E.-July, 2006

Indicates Battery Charging CurrentAnyone who has ever had a shocking experience on an especially dry day is acutely aware of the kinds of high voltage that can be generated from a simple walk across a carpeted floor.  Those same finger to metal sparks can destroy or disrupt sensitive elect . . . Hobby Circuit designed by Dave Johnson P.E.-January, 2011

Indicator for Acceptable VoltageI have used this circuit many times in custom test fixtures where a simple go-no go indication was needed.  The circuit can also be used to adjust a particular voltage be within specific high or low limits.  The three LEDs will indicate if the voltage is . . . Hobby Circuit designed by David Johnson P.E.-February, 2002

Indicator for Bad Light BulbThis request came from a Discover Circuits visitor.  He wanted to turn on a LED indicator light whenever a circuit detected a burned out tail/brake light on a car or truck.  The circuit shown below uses a transistor switch, to detect current flowing through a low value resistor . . . Hobby Circuit designed by David Johnson P.E.-December, 2006

IR Remote LED Indicator LightThere are times when you would like to transmit a signal from one LED indicator light to second LED at another location.  The circuit below works well for this application.  It takes advantage of the fact that the internal infrared LED inside an opto-isolator. . . Circuit by Dave Johnson P.E.-December, 2008


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

Game Show Indicator Lights (Who's First) -  This circuit turns on a light corresponding to the first of several buttons pressed in a "Who's First" game.  Three stages are shown but the circuit can be extended to include any number of buttons and lamps.  Three SCRs  (silicon controlled rectifiers) are connected with a common cathode resistor  (50 ohm) so that when any SCR conducts, the voltage on the cathodes will rise about 7 volts above the voltage at the junction of the 51K and 1K ohm resistors and prevent triggering of a second SCR.  When all lamps are off, and a button is pressed, the corresponding SCR is triggered due to

Game Show Who's First Indicator Lights -  The circuit above turns on a light corresponding to the first of several buttons pressed in a "Who's First" game.  Three stages are shown but the circuit can be extended to include any number of buttons and lamps.  Three SCRs  (silicon controlled rectifiers) are connected with a common cathode resistor  (50 ohm) so that when any SCR conducts, the voltage on the cathodes will rise about 7 volts above the voltage at the junction of the 51K and 1K ohm resistors and prevent triggering of a second SCR.  When all lamps are off, and a button is pressed, the corresponding SCR is triggered due __ Designed by Bill Bowden

Garage Light Indicator LED -  This is the simplest possible way to power an LED off 115VAC.    I epoxied a high-brightness yellow LED into the switch plate to my garage light.  The light switch is inside my house, but the garage light cannot be seen when the door is closed.    This has cau __ Designed by Andrew R. Morris

Ground Fault Indicator -  Check out your AC Outlets for Possible Hazzards.   __ Designed by G.L. Chemelec

High DC Current Indicator -  A while back, someone requested a simple method to indicate when 20 to 50 amps of DC current was flowing through a wire.  The circuit below works well and is about as simple as you can get.  A sensitive reed relay . . . Hobby Circuit designed by David Johnson P.E.-April, 2005

High Intensity Line Powered LED Flasher -  There are times when you would like to generate an intensely bright flash of light using electrical power from the AC line.  The circuit below can drive a one to three watt power LED with about 350ma of peak current.  Since the circuit drives the LED with. . . Circuit by David Johnson P.E.-December, 2008

Hot AC Power Line Indicator -  The circuit below is designed to detect when a power cable is active  (hot) .  When the flat sensor end of the device is held near an active AC line, the bright green LED on the top of the housing will glow.  It is powered by a 3v CR2032 lithium coin cell.  I . . . Hobby Circuit designed by Dave Johnson P.E.-May, 2005

Hot Water Tank Indicator -  The idea for this project may have come to me in a flash of inspiration, and its a very simple way to check if a fuse has blown without removing it from its holder __ Designed by Andy Collison

Humidity Indicator & Controller -  Presented here is a simple humidity indicator and controller.  In industries such as textile, the change in moisture content has a direct impact on the properties of fabric, such as tensile...__ Electronics Projects for You

Improved Infrared Receiver with status led -  This is a general purpose serial port infrared receiver.  With the help of appropriate software  (see below) you can control different functions of your pc from a distance.  For example you can control your home cinema settings  (volume, play, pause, stop etc) , your winamp etc __ Contact: IQ Technologies

Incoming call indicator -  It is a relatively simple circuit, with which we can have optical and sound clue, when we have telephone ring in the line of telephone.  The calls in the line, are changed in pulses of frequency 400 HZ from the IC2, in exit 3.  Then via the IC4, after they are strengthened at two times, they can be drive to the entry of amplifier and a loudspeaker, so that we hear the ring, in what level we want.  The desirable level of sound __ Designed by Sam Electronic Circuits 8/01

Indicate DC Current Flow -  The circuit below is a simple way to indicate when DC current is flowing through a wire.  The circuit is designed so it will turn on a LED indicator light, whenever the voltage drop across a shunt resistor exceeds about 0.1volts.  The value of the resist . . . Hobby Circuit designed by Dave Johnson P.E.-October, 2005

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

Indicates 120 VAC or 240 VA - C -  Two LEDs indicate if a power line has 120vac or 240vac voltage on it . . . Hobby Circuit designed by David A. Johnson P.E.-January, 2007

Indicates a Low battery -  02/03/14EDN-Design Ideas It may seem a bit counterintuitive to power on an LED when a battery is already low, but this Design Idea does it with aplomb __ Circuit Design by James Wood

Indicates Automotive Electrical Voltage -  When troubleshooting the 12v electrical system of an automobile, it is nice to have a simple voltage indicator tool instead of a voltmeter.  This electronic circuit, hobby circuit is powered by two AA or even two N cells, which will provide enough energy . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

Indicates Battery Charge Current -  This circuit turns on a LED whenever it detects at least 25ma of battery charge current . . . Hobby Circuit designed by David A. Johnson P.E.-July, 2006

Indicates Battery Charging Current -  Anyone who has ever had a shocking experience on an especially dry day is acutely aware of the kinds of high voltage that can be generated from a simple walk across a carpeted floor.  Those same finger to metal sparks can destroy or disrupt sensitive elect . . . Hobby Circuit designed by Dave Johnson P.E.-January, 2011

Indicates when Power is Lost -  Dave Campbell designed this clever circuit.    It uses two neon lamps to indicate if power to a 120vac appliance had been interrupted.   __ Designed by Dave Campbell, Boulder CO

Indicator features expanded scale -  02/21/02  EDN-Design Ideas Test equipment for a production line should be user-friendly  (read "idiot-proof"] and should offer minimal test time.  In many cases, the test fixture must give an operator only one answerpass or fail.  Usually, two indicators assum __ Circuit Design by Abel Raynus, Armatron International, Melrose, MA

Indicator for Acceptable Voltage -  I have used this circuit many times in custom test fixtures where a simple go-no go indication was needed.  The circuit can also be used to adjust a particular voltage be within specific high or low limits.  The three LEDs will indicate if the voltage is . . . Hobby Circuit designed by David Johnson P.E.-February, 2002

Indicator for Bad Light Bulb -  This request came from a Discover Circuits visitor.  He wanted to turn on a LED indicator light whenever a circuit detected a burned out tail/brake light on a car or truck.  The circuit shown below uses a transistor switch, to detect current flowing through a low value resistor . . . Hobby Circuit designed by David Johnson P.E.-December, 2006

Indicator for Dynamic Limiter -  NOTE : Must register on this site __ Designed by Published in Elecktor July/Aug, 2010

Indicator Has "Electronic Lens" -  4-Sep-03 EDN-Design Ideas The method for implementing an extended-scale meter described in an earlier Design Ideas had a conceptual error  The meter impedance must change continuously, not discretely as expressed (Reference 1].  You could achieve the desired result by using a digital potentiometer controlled by an input voltage via an appropriate interface __ Circuit Design by Abel Raynus, Armatron International Inc, Melrose, MA

IR Remote LED Indicator Light -  There are times when you would like to transmit a signal from one LED indicator light to second LED at another location.  The circuit below works well for this application.  It takes advantage of the fact that the internal infrared LED inside an opto-isolator. . . Circuit by Dave Johnson P.E.-December, 2008

Isolated indicator signals telephone line's status -  06/08/06  EDN-Design Ideas Micropowered circuit shows off-hook phone __ Circuit Design by Yongping Xia, Navcom Technology, Torrance, CA


Indicator Circuits
Indicators:  #'s - A       B - C       D - F       G - I       J - L       M - P        R - S       T - Z

 


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