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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

Circuits Designed by Dave Johnson, P.E. :

DC Current Bidirectional Indicator This circuit is handy for battery powered systems.  The circuit is self-powered using a single 3v lithium coin cell.  The current draw is so low that the battery should last for years.  The hobby circuit flashes a red LED when DC current is drawn from the battery and flashes a green LED whenever current flows into the battery.  Two “probe” input wires connect across a section of cable, which acts as a shunt resistor.  A voltage of only 5mv in either direction will trigger a LED indication . . . Hobby Circuit designed by Dave Johnson P.E.-March, 2011

DC Current Indicator #4The circuit below uses some common components to turn on an LED whenever DC current above a certain level is detected.  The circuit uses a very popular LM393 dual voltage comparator from National Semiconductor and a common 1N4148 signal diode.  The diode. . . Circuit by David Johnson P.E.-October, 2005

DC Current Indicator 6The 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. . . Circuit by David Johnson P.E.-October, 2005

Detects Xenon Lamp FlashThis circuit has a very low standby current requirement yet has very high sensitivity toward the light flashes from a xenon lamp.  When connected to a flip/flop it can serve as an on on/off Controller . . . Hobby Circuit designed by Dave Johnson P.E.-December, 2004

Does Power Line have 120 VAC or 240 VAC?Two LEDs indicate if a power line has 120vac or 240vac voltage on it. . . Circuit by David Johnson P.E.-July, 2006

Either indicates 120 VAC or 240 VAC  - Two LEDs indicate if a power line has 120vac or 240vac voltage on it. . . Circuit by David A. Johnson P.E.-July, 2006

Electrical Current IndicatorI designed this circuit as a simple current indicator for any load ranging from 40 watts to 250 watts.  The circuit turns on a small LED, whenever it detects current flowing to a remote load. . . Circuit by David Johnson P.E.-October, 2005

Fake Car Alarm LightWhenever the car’s ignition is turned off, this circuit activates a flashing LED, which can be positioned to appear as an active alarm system. . . Circuit by David A. Johnson P.E.-October, 2005

Flashing LED Power Indicator This circuit flashes a power indicator LED to keep the average current low. . . Circuit by Dave Johnson P.E.-June, 2000

Flashing Light to simulate Car AlarmWhenever the car’s ignition is turned off, this circuit activates a flashing LED, which can be positioned to appear as an active alarm system . . . Hobby Circuit designed by Dave Johnson P.E.-October, 2005

Four Line Telephone Line Status IndicatorMany home businesses use multiple phone lines.  This circuit gives you a visual indication when a line is in operation.  The two AA battery cells should provide enough power for about one year of operation. . . Circuit by David A. Johnson P.E.-June, 2000

Front Desk Service BeeperThis device functions like a lobby desk service request bell.  A short beep is sounded whenever the large pushbutton on top of the device is pressed.  Once pressed, the device will not make another beep until at least 2 minutes of time has elapsed . . . Hobby Circuit designed by David Johnson P.E.-September, 2005


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

Data Multiplexer Adds Cursor to LED Display Driver -  03/30/95 EDN-Design Ideas A data multiplexer, IC2, enables the LED-display driver, IC1, in Fig 1 to highlight any selected digit by intensifying its brightness.  This cursor function enables the use of the display for data entry as well as readout.  For example, the operator of an environmental chamber can set a desired temperature by entering that value via the display.    __ Circuit Design by Gary Sellani, Maxim Integrated Products, Sunnyvale, CA

DC Current Bidirectional Indicator -  This circuit is handy for battery powered systems.  The circuit is self-powered using a single 3v lithium coin cell.  The current draw is so low that the battery should last for years.  The hobby circuit flashes a red LED when DC current is drawn from the battery and flashes a green LED whenever current flows into the battery.  Two “probe” input wires connect across a section of cable, which acts as a shunt resistor.  A voltage of only 5mv in either direction will trigger a LED indication . . . Hobby Circuit designed by Dave Johnson P.E.-March, 2011

DC Current Indicator #4 -  The circuit below uses some common components to turn on an LED whenever DC current above a certain level is detected.  The circuit uses a very popular LM393 dual voltage comparator from National Semiconductor and a common 1N4148 signal diode.  The diode. . . Circuit by David Johnson P.E.-October, 2005

DC Current Indicator 6 -  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. . . Circuit by David Johnson P.E.-October, 2005

Detects Xenon Lamp Flash -  This circuit has a very low standby current requirement yet has very high sensitivity toward the light flashes from a xenon lamp.  When connected to a flip/flop it can serve as an on on/off Controller . . . Hobby Circuit designed by Dave Johnson P.E.-December, 2004

Digital Mains Voltage Indicator -  This is a circuit for a digital mains voltage indicator that displays main voltage in the form of a LED bar graph with 16 LEDs.  The first LED indicates voltage level at 50 V and the 16th LED shows voltage level for 280 V__ Electronics Projects for You

Digital Mains Voltage Indicator -  Continuous monitoring of the mains voltage is required in many ap- plications such as manual voltage stabilisers and motor pumps.  An analogue voltmeter, though cheap, has many disadvantages as it has moving parts and is sensitive to vibrations.  The __ Designed by Radio LocMan

Does Power Line have 120 VAC or 240 VAC? -  Two LEDs indicate if a power line has 120vac or 240vac voltage on it. . . Circuit by David Johnson P.E.-July, 2006

Doorbell for the Deaf -  This circuit provides a delayed visual indication when a door bell switch is pressed.  In addition, a DPDT switch can be moved from within the house which will light a lamp in the door bell switch.  The lamp can illuminate the words "Please Wait" for anyone with walking difficulties __ Designed by Andy Collison

Doorbell-Cum-Visitor Indicator -  This doorbell circuit can also give identification of the visitor to your home in your absence.  When you’re home, you can use it simply as a normal doorbell.  The circuit  (see Fig....__ Electronics Projects for You

Earth Fault Indicator -  The security of many electrical devices depends today on the availability of an earthed mains outlet.  We should remember that these are connected to the frame or to the metal housing of the equipment and so it routes to the protective earth  (PE) connections.  In this setup, mains voltage, however small, will cause the differential

Earth Fault Indicator -  In mains-powered equipment, exposed metal parts are connected to earth wire in order to prevent users from contact with high voltages if electrical insulation fails.  Connections to ground through earth connection...__ Electronics Projects for You

Earthquake Indicator using Arduino -  An earthquake is an unavoidable and unpredictable natural phenomenon that often causes damage to lives and property.  We cannot fight it but we can stay alert and aware using technology that...__ Electronics Projects for You

Either indicates 120 VAC or 240 VAC  -  Two LEDs indicate if a power line has 120vac or 240vac voltage on it. . . Circuit by David A. Johnson P.E.-July, 2006

Electrical Current Indicator -  I designed this circuit as a simple current indicator for any load ranging from 40 watts to 250 watts.  The circuit turns on a small LED, whenever it detects current flowing to a remote load. . . Circuit by David Johnson P.E.-October, 2005

Electronic Watch Dog -  Here’s an electronic watch dog for your house that sounds to inform you that somebody is at the gate.  The circuit comprises a transmitter unit and a receiver unit, which are...__ Electronics Projects for You

Expanded-scale indicator revisited -  08/08/02 EDN-Design Ideas The visualization aid that a previous Design Ideas describes allows only the expansion of the upper end of the scale (Reference 1].  But what can you do if, according to your project requirements, you need to expand the middle region of the scale? Figure 1a illustrates the challenge.  A voltmeter comprises a 100-µA dc meter and a series resistor __ Circuit Design by Abel Raynus, Armatron International Inc, Melrose, MA

Fake Car Alarm Light -  Whenever the car’s ignition is turned off, this circuit activates a flashing LED, which can be positioned to appear as an active alarm system. . . Circuit by David A. Johnson P.E.-October, 2005

Fastest Finger First -  This project describes a "Fastest Finger First" system that is cheap to build, has high noise immunity, is reliable and is also extensible.  Note that whilst the schematic below may look complicated, its actually a very simple & cheap interlock based round a single 4013 dual d-type flip-flop and an output driver that is replicated for each positionin this example, 8 times.  The buzzer is also optional and can be omitted, along with all its associated components.  The few extra resistors & capacitors used for improving the noise immunity are very cheap but improve the reliability of the design greatly.  i.e.  it's a proper design rather than a hack! __ Designed by Nick de Smith

Fastest Finger First Indicator -  Quiz-type game shows are increasingly becoming popular on television these days.  In such games, fastest finger first indicators  (FFFIs) are used to test the player’s reaction time.  The player’s designated number...__ Electronics Projects for You

Fastest Finger First Indicator -  The above image shows the circuit diagram of Fastest Finger First Indicator which is used to make the project and has been taken from EFY.  This project is an electronic quiz buzzer that is affordable by the colleges and even individuals.  This project is useful for a 4-team quiz contest, although it can be modified for more number of teams.  Use this report for your reference and study only and thanks to all authors.   __ Designed by Krity Vats, Divya Uniyal, Garima Sharma

Fastest Finger First System using Raspberry Pi -  Fastest finger first systems are used in school, college and TV contests.  The team which presses their push-button switch first is entitled to answer the query.  When two or more teams...__ Electronics Projects for You

Faulty Car Indicator Alarm -  Before taking a turn, either left or right, car drivers need to switch on the car’s turn-indicator lamps so that the approaching vehicle drivers can take precaution accordingly.  An accident is...__ Electronics Projects for You

Flash ADC takes the uncertainty out of high-speed data recover -  09/01/98 EDN-Design Ideas Flash ADC takes the uncertainty out of high-speed data recoveryTraditional methods of recovering data and clock information from noisy baseband signals fail at data rates higher than 30 Mbps.  Using the same flash ADC to sample both the input data and its phase eliminates timing errors and makes it possible to recover data at 500 Mbps.   __ Circuit Design by Tom Napier, Consultant

Flash an LED From Ac-Mains Power -  01/06/11 EDN-Design Ideas A few components create an illuminated switch __ Circuit Design by TA Babu, Chennai, India

Flashing LED Power Indicator -  This circuit flashes a power indicator LED to keep the average current low. . . Circuit by Dave Johnson P.E.-June, 2000

Flashing Light to simulate Car Alarm -  Whenever the car’s ignition is turned off, this circuit activates a flashing LED, which can be positioned to appear as an active alarm system . . . Hobby Circuit designed by Dave Johnson P.E.-October, 2005

Flashing-LED Battery-status Indicator -  Signals when an on-circuit battery is exhausted; 5V to 12V operating voltage __ Contact: Flavio Dellepiane, fladello @ tin.it

Flat Battery Indicator -  This small circuit was developed to monitor the battery in a model hovercraft.  The lift in the model is produced by an electric motor driving a fan.  To avoid the possibility of discharging the rechargeable battery pack too deeply, the design lights a conspicuous LED mounted on the model when a preset threshold voltage is

Form Low-Frequency Circulator -  10/11/01 EDN-Design Ideas The electronic circulator made its debut ten years ago  (Reference 1].  It functioned at VHF as a three-port unit using a Comlinear  (now part of National Semiconductor, www.  nsc.  com] CLC 406 operational amplifier.  The circuit in Figure  __ Circuit Design by Richard Kurzrok, Queens Village, NY

Form Peak/Clipping Indicator -  11/22/01 EDN-Design Ideas The simple peak detector in Figure 1 is the result of a need for a single-5V-supply, level/clipping indicator for a multimedia-PC sound system.  The design is unique in that it detects both stereo channels on a single peak-hold capacitor.  All the adjustments in the circuit simultaneously apply to both left and right stereo inputs __ Circuit Design by Steven Hageman

Four Line Telephone Line Status Indicator -  Many home businesses use multiple phone lines.  This circuit gives you a visual indication when a line is in operation.  The two AA battery cells should provide enough power for about one year of operation. . . Circuit by David A. Johnson P.E.-June, 2000

Four-Level Audio Power Indicator -  Self-powered Unit; Simple circuitryLow parts count __ Contact: Flavio Dellepiane, fladello @ tin.it

Free-line indicator stops interruptions -  12/07/00 EDN-Design Ideas When only one phone line is available for two phones, each time you want to make a call, someone may be using the second phone.  A simple circuit lights an LED, which indicates whether the line is free (Figure 1a].  Batteries are unnecessary; the phone line powers the circuit, and an accumulator saves energy for an "in use" indicationscroll to find this circuit __ Circuit Design by JM Terrade, Clermont-Ferrand, France

Front Desk Service Beeper -  This device functions like a lobby desk service request bell.  A short beep is sounded whenever the large pushbutton on top of the device is pressed.  Once pressed, the device will not make another beep until at least 2 minutes of time has elapsed . . . Hobby Circuit designed by David Johnson P.E.-September, 2005

Fuel Reserve Indicator for Vehicles -  Here is a simple circuit for monitoring the fuel level in vehicles.  It gives an audiovisual indication when the fuel level drops alarmingly below the reserve level, helping you to avoid...__ Electronics Projects for You

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

Fuse-Cum-Power Failure Indicator -  This fuse-cum-power failure indicator comprises an LED  (LED1) , light-dependent resistor  (LDR1) , inverter circuit and two timer circuits built around IC NE555.  LDR1 and preset VR1 form a voltage divider at the...__ Electronics Projects for You


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

 


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