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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. :

Lead-Acid Battery Low Voltage IndicatorLead-acid batteries should not be discharged below a certain voltage.  Discharging a cell below about 1.8v and can often damage it, which will result in a lower amp-hour capacity.  Large battery banks are critical in off-grid energy storage systems.  One. . . Circuit by Dave Johnson P.E.-July, 2006

LED Flasher needs only 1.5 VOLTSTo squeeze even more energy from a alkaline battery cell, this circuit adds two transistors to a circuit similar to the above design to boost the efficiency.  A small 1.5 volt alkaline N cell should flash the LED for a full year.  It too uses a "charge pump" technique to provide a LED the needed voltage . . . Hobby Circuit designed by David Johnson P.E.-June, 2000

Line Powered High Intensity 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 . . . Hobby Circuit designed by David Johnson P.E.-December, 2008

Line Status Indicator for 1 Telephone LineThis circuit monitors one phone line . . . Hobby Circuit designed by Dave Johnson P.E.-June, 2000

Low Battery Voltage FlasherThis circuit is designed to monitor two alkaline cells (3v) that form the battery often used in portable electronic equipment. . . Circuit by Dave Johnson P.E.-January, 1998

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

Low Power LED FlasherJudging from the numerous references I have received, this electronic circuit, hobby circuit seems to be rather popular.  Many published circuits which flash LEDs need 3 or more volts.  This electronic circuit uses only a single inexpensive C-MOS IC and . . . Hobby Circuit designed by Dave Johnson P.E.-June, 2000

Low Voltage Indicator for Lead-Acid BatteryLead-acid batteries should not be discharged below a certain voltage.  Discharging a cell below about 1.8v and can often damage it, which will result in a lower amp-hour capacity.  Large battery banks are critical in off-grid energy storage systems.  One . . . Hobby Circuit designed by David Johnson P.E.-July, 2006


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

Jeopardy (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

Lead-Acid Battery Low Voltage Indicator -  Lead-acid batteries should not be discharged below a certain voltage.  Discharging a cell below about 1.8v and can often damage it, which will result in a lower amp-hour capacity.  Large battery banks are critical in off-grid energy storage systems.  One. . . Circuit by Dave Johnson P.E.-July, 2006

LED Battery Condition Indicator -  In the circuit below, a quad voltage comparator  (LM339) is used as a simple bar graph meter to indicate the charge condition of a 12 volt, lead acid battery.  A 5 volt reference voltage is connected to each of the  (+) inputs of the four comparators and the  (-) inputs are connected to successive points along a voltage divider.  The LEDs __ Designed by Bill Bowden

LED Flasher Indicates Low Battery Condition -  01/02/97 EDN-Design Ideas Many portable electronic devices could benefit from a visual indication when their battery requires replacement.  Typical low-battery indicators simply turn on an LED when the battery voltage drops below a certain value.  Such circuits actually accelerate the battery's extinction by drawing excessive current.  The circuit in Figure 1 draws a mere 1 m A in its standby mode and averages only 20 m A when activated.  The low current imposes a minimal burden on any battery circuit.  An off-the-shelf, undervoltage sensor IC (IC1) monitors the battery voltage--  __ Circuit Design by David Johnson, DiscoverCircuits.com

LED Flasher needs only 1.5 VOLTS -  To squeeze even more energy from a alkaline battery cell, this circuit adds two transistors to a circuit similar to the above design to boost the efficiency.  A small 1.5 volt alkaline N cell should flash the LED for a full year.  It too uses a "charge pump" technique to provide a LED the needed voltage . . . Hobby Circuit designed by David Johnson P.E.-June, 2000

LED Indicates Power Source -  08/26/10 EDN-Design Ideas A zener diode lets detects the presence or absence of a power source.   __ Circuit Design by Brian Conley, PE, Circuitsville Engineering LLC

LED Indicates Two Power States -  12/05/96 EDN-Design Ideas  Uses a single bicolor LED to indicate both power-on and blown-fuse conditions.    __ Circuit Design by Jim Hagerman, Hagerman Technology, San Diego, CA

LED Programmable Indicator -  This circuit uses CD4017 to program a bicolour LED in ten different modes with combinations of red and green.  __ Electronics Projects for You

LED Voltage Indicator -  This teensy little board is only 1 inch  (25mm) square, and is handy as a combined power on and low battery voltage indicator.  The two colour LED changes from green to red when the battery voltage drops below the adjustable trigger voltage.  It's usable between about 6V and 30VDC, and uses a precision LM336Z-2.5 voltage reference.  The LED can be reversed so it changes from green to red if the preset voltage is exceeded, if required.   __ Designed by Bob Barker, not the TV Host

LEDs Indicate Sound Level -  08/25/11  EDN-Design Ideas Build a battery-operated portable meter to measure sound-pressure levels.   This Design Idea describes a battery-operated, portable soundlevel meter  (Figure 1) .  Its portability makes it useful for detecting the source of noise in automotive engines and power trains, factory machinery, and residential HVAC  (heating/ventilation/air-conditioning) systems __ Circuit Design by Stephen Kamichik, Ile Bizard, PQ, Canada

LEDs Light LAN-Cable Tester -  12/02/10 EDN-Design Ideas A series of LEDs indicate the health of an Ethernet cable.  [Design Ideas by Noureddine Benabadji, University of Sciences and Technology, Oran, Algeria __ Circuit Design by Noureddine Benabadji, University of Sciences and Technology, Oran, Algeria

Level indicator with 10 LED -  Schematic + PBC layout __ Jan Kolar

Line busy indicator -  This circuit flashes an LED if the phone line is in use or is ringing.  It is powered by the phone line, and it uses so little current that several of them could be used on the same line without interference.   When first connected, let the circuit charge on __ Designed by Andrew R. Morris

Line Powered High Intensity 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 . . . Hobby Circuit designed by David Johnson P.E.-December, 2008

Line Status Indicator for 1 Telephone Line -  This circuit monitors one phone line . . . Hobby Circuit designed by Dave Johnson P.E.-June, 2000

LM741 OpAmp Voltage Indicator -  Plans for a simple voltage high/low indicator built around an LM741 operational amplifier.   __ Designed by REUK-Renewable Energy UK website

Logic ‘High’/’Low’ Indicator -  This logic 'high'/'low' indicator circuit comprises two ICs.  One is hex inverter IC 7404  (IC1) and the other is a bistable multivibrator built around timer IC 555  (IC2) .  A logic probe...__ Electronics Projects for You

Loudspeaker Peak Indicator -  Modern loudspeakers boxes are relatively insensitive to overdriving signals, however it is still important to limit the power driving it to avoid clipping of the audio signal.  A broken sound from an overdriven loudspeaker is not only annoying to the the ears but also the loudspeaker itself can be damaged by the continous __ Designed by Popescu Marian

Low Battery Indicator -  File contains several designs, please scroll to find this circuit.  Here is a low battery indicator that flashes a lamp when the battery voltage falls below about 5 volts.  The circuit draws about 25 microamps when not flashing so battery life is not significantly shortened by the circuit.  The two 1 megohm resistors set the switching point at V/2  (plus a little due to the emitter-base diode drop) and when this voltage is above the zener voltage the circuit cannot turn on.  When the battery voltage drops below 5 volts, the base voltage drops to 2.5 volts and the emitter can reach a voltage sufficient to turn on the PNP  (2N4403 or similar) .  When the PNP conducts, the NPN also conducts dropping the voltage across the circuit even more and the circuit snaps on.  When the 4.7 uF capacitor has discharged, the circuit turns off and the capacitor begins charging again.   __ Contact: Charles Wenzel of Wenzel Associates, Inc.

Low Battery Indicator Ii -  This circuit indicates the remaining battery life bAy varying the duty cycle and flash rate of an LED as the battery voltage decreases.  In fact, the circuit actually indicates five battery conditions:  (1) a steady glow assures indicates that the battery is healthy;  (2) a 2Hz flicker  (briefly off) indicates that the battery is starting

Low Battery Voltage Flasher -  This circuit is designed to monitor two alkaline cells  (3v) that form the battery often used in portable electronic equipment. . . Circuit by Dave Johnson P.E.-January, 1998

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

Low Power LED Flasher -  Judging from the numerous references I have received, this electronic circuit, hobby circuit seems to be rather popular.  Many published circuits which flash LEDs need 3 or more volts.  This electronic circuit uses only a single inexpensive C-MOS IC and . . . Hobby Circuit designed by Dave Johnson P.E.-June, 2000

Low Voltage Indicator for Lead-Acid Battery -  Lead-acid batteries should not be discharged below a certain voltage.  Discharging a cell below about 1.8v and can often damage it, which will result in a lower amp-hour capacity.  Large battery banks are critical in off-grid energy storage systems.  One . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

Low-Battery Indicator has High-Efficiency -  05/03/01 EDN-Design Ideas The usual method for implementing the low-battery warning featured in most battery-operated equipment is to illuminate an LED.  However, the LED exacerbates the low-battery condition.  You can greatly reduce the LED's power consumption by operating it at a low frequency and a low duty cycle.   __ Circuit Design by Joe Neubauer

Low-Battery Indicator Uses Fleapower -  4-Sep-03 EDN-Design Ideas It is always desirable to use a low-battery indicator that consumes as little power as possible.  For a 9V, 450-mAhr alkaline battery, a 50-µA low-battery indicator can by itself run the battery down in a littlethan a year.  Battery-powered devices that need to run continuously for a long time require battery indicators that consume minimal power __ Circuit Design by Yongping Xia, Navcom Technology, Redondo Beach, CA

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


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

 


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