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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. :

Moving AIR IndicatorMany months ago a Discover Circuits reader wanted a method to indicate when a fan was blowing air.  He didn’t want to route any electrical wires to a sensor near the fan.  Instead he wanted all the electronics for both the fan and other circuits mounted s . . . Hobby Circuit designed by Dave Johnson P.E.-August, 2006

One-Line Telephone Line Status Indicator This circuit monitors one phone line. . . Circuit by David A. Johnson P.E.-June, 2000

Piezoelectric Water Flowing IndicatorThe vibrations associated with water flowing through a pipe are picked up by an inexpensive piezo wafer.  The signal from the wafer is first boosted by a micropower transistor amplifier and then fed to an ultra low power voltage comparator . . . Hobby Circuit designed by David Johnson P.E.-July, 2009


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

Mains Interruption Counter with Indicator -  This circuit counts mains supply interruptions  (up to 9) and shows the number on a 7-segment display.  It is highly useful for automobile battery chargers.  Based on the number of mains interruptions, the user can extend the charging time for lead-acid batteries.   __ Designed by Electronics Projects for You

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

Maximum Minimum Voltage Indicator -  This circuit indicates which of three voltages in the range from about about -4V to about +4V – at A, B and C – is the highest by lighting one of three indicator LEDs.  Alternatively, it can be wired to indicate the lowest of three voltages or to indicate both the highest and lowest voltages.

Message Waiting Flasher -  This circuit starts flashing a neon light when the phone rings and continues flashing it until the phone is picked up to remind you to check your voice-mail.  The flashing neon light drives a voltage doubler  (Q2) which keeps it flashing.  Q1 ensures that the __ Designed by Andrew R. Morris

Model Aeroplane Navigation Strobe/Battery Level Indicator  -  If you are interested in model aeroplanes and have the capital, a radio controlled electric park flyer is a must have.  An RC aeroplane under 400 grams floats around like the rubber models of my youth and contact with the ground doesn't seems to involve that sickening crunch __ Contact: r dot p @ webone.com.au

Moving AIR Indicator -  Many months ago a Discover Circuits reader wanted a method to indicate when a fan was blowing air.  He didn’t want to route any electrical wires to a sensor near the fan.  Instead he wanted all the electronics for both the fan and other circuits mounted s . . . Hobby Circuit designed by Dave Johnson P.E.-August, 2006

Multi-Switch Doorbell with Indicators -  Here’s the circuit of a multi-switch input musical doorbell  (shown in Fig.1) .  The circuit is built around the popular and less expensive quad D-latch CD4042B  (IC1) .When switch S6 is pushed to...__ Electronics Projects for You

Off-Hook Indicator for Telephone Lines -  A "busy" indicator to prevent annoying interruptions to internet access.__ SiliconChip

Off-Hook Phone Line Supplies 150 m -  09/01/94 EDN-Design Ideas For systems that require 150 mW or less, the power supply in Fig 1 draws power from ordinary phone jacks without interrupting the voice signal, thereby eliminating the need for batteries and ac adapters.  Built into peripheral equipment such as PCMCIA modem cards, this circuit can spare the battery in a host computer.  The circuit is __ Circuit Design by Ron Clark and Bob Underwood, Maxim Integrated Products, Sunnyvale, CA

One-Line Telephone Line Status Indicator -  This circuit monitors one phone line. . . Circuit by David A. Johnson P.E.-June, 2000

One-Of-Nine Switch Position Indicator -  Originally conceived as a track-in-use indicator for model railway layouts, this one-of-nine indicator can used with any selector switch with up to nine positions.  It can be used with a bank of reed switches, as might be used on a locomotive turntable or traverser on a model railway layout or with any switch with up to nine positions.  Then we realised it had many other uses __ SiliconChip

Op-Amp Rectifier Signals Input State -  07/21/94 EDN-Design Ideas The op-amp rectifier in Fig 1 operates from a single supply and provIdeas a logic output and an LED that indicate the state of the input voltage.  The input-state indications are handy for calibration.  Because the circuit operates from a single supply, the 2.5V reference determines the level around which the circuit rectifies input waveforms __ Circuit Design by Lee E Scaggs, High Country TEK, Nevada City, CA

Overflow Water-Tank Indicator -  Water is a vital but scarce natural resource.  To prevent water wastage, this water-tank overflow indicator comes in handy.  It gives audio as well visual alarm whenever the water tank overflows.Fig....__ Electronics Projects for You

Over-Heating Indicator for Water Pipe -  The hot water pipe from the water geyser of your bathroom may burst if it gets overheated and is left unattended.  This circuit monitors the temperature of the water pipe.  If...__ Electronics Projects for You

Over-Speed Indicator -  This circuit is designed for indicating over-speed and direction of rotation of the motor used in mini hand tools, water pump motors, toys and other appliances.  A 12V DC motor  (M1) is...__ Electronics Projects for You

Park Aid -  Three LEDs signal bumper-barrier distance; Infra-red operation, indoor use __ Contact: Flavio Dellepiane, fladello @ tin.it

Park-Aid Modification -  Three-step beeps signal bumper-barrier distance; Infra-red operation, indoor use __ Contact: Flavio Dellepiane, fladello @ tin.it

Peak Level Indicator -  Dot-mode three-LED display.9V battery powered portable unit __ Contact: Flavio Dellepiane, fladello @ tin.it

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

Pencell Charge Indicator -  Small-size AA cells and button cells used in electronic devices providing a terminal voltage of 1.5V are normally rated at 500 mAh.  As the cells discharge, their internal impedance increases to...__ Electronics Projects for You

Phase-sequence indicator uses few passive components -  07/06/06 EDN-Design Ideas Debug three-phase power-line wiring with this easily constructed circuit __ Circuit Design by Metodi Iliev, University of California—Berkeley

Phone Busy Indicator -  Simple busy indicator, does not meet regulations of many countries because this circuit draws excessive continuous current from the ph1-line even when not active and this can cause problems with Telephone system.   __ Designed by Aaron Cake

Phone in use indicator 1 -  Use a CMOS 4049 Hex Interter because  (supposedly) has high drive output.  And since it's CMOS , it can operate with Vcc from +3 to +15V.  And it has a high input impedence.   __ Designed by Roger Petersen

Phone in use indicator 2 -  LED will start blinking if a phone is in use

Phone in use indicator 3 -  Now here's some logic that should work fine with the right zener and the right resistors and a couple of cheap NPN's 2n2222A's or 2n3904's  (06's?) .  If you get close to 25 volts with the new smart test boxes, a 20 volt Z may work fine.  Choose R1 to limit current through Z and have enough left to turn on NPN1 just enough to deprive NPN2, choose R2 for that, and you will need to add a resistor R3 to protect the LED from overcurrent as needed, depending on the phone system you have!
 __ Designed by Richard Steven Walz

Phone in use indicator 4 -  The circuit I built gives a visual indication at each extension when any extension is off-hook.  It is line-powered, and the maximum number that can be used on our system is three.  Since they all draw power at the same time to light the LEDs, any more indicators would cause an off-hook condition.  Some changes could be made to reduce the current draw, to allow using more indicators, but the brightness of each led would suffer.  The LEDs I used are tiny, but.   __ Designed by Kenneth Carver

Phone in use indicator 5 -  Schematic only, no description included __ Designed by Terri Barber

Phone in use indicator 6 -  R1 and R2 form a voltage divider, insuring that the phone line sees a high impedance load and that high voltages  (such as the ring voltage) are easily dissipated by the protective diodes  (CR1 and CR2) .  Also  (obviously) they serve to divide all incoming voltages by two.  Capacitor C1 filters out some of the audio signals that might otherwise make the LED flicker with speech

Phone in use indicator 7 -  LED will light up if a phone is in use.   __ Designed by Schematic only, no description included

Phone Light Flasher -  This is very useful in a situation were there is lots of noise and it is impossable to hear the phone, such as a workshop.  Here is such a device.  The ring detect part of this circuit came from [url]http://www.  hut.  fi/Misc/Electronics/circuits/telephone_ringer.  html[/url].  Notes: 1.  You may need to use a lower voltage zener for D1 and D2.2.  You can use a regular relay instead of a solid state relay, but the arcing accross the contacts may destroy it pretty quickly.3.  Be very sure that you have not accidentally connected 120V to the phone line when building and installing this __ Designed by Aaron Cake

Phone Line In-Use Indicators -  Presented are two different designs that perform the same function.  Each circuit lights an LED when a telephone line is in use, and can be placed at extension telephones to alert others not to interrupt.  Unlike "off-hook" indicator circuits, these circuits do not have to be inserted in series with the telephone; they are simply plugged into the telephone line to provide an indication that one or more of the phones on that line are being used.  Both circuits are powered by 9v batteries, and therefore present little danger of imposing an unsafe condition on the telephone line or equipment.   __ Designed by Arthur Harrison

Piezoelectric Water Flowing Indicator -  The vibrations associated with water flowing through a pipe are picked up by an inexpensive piezo wafer.  The signal from the wafer is first boosted by a micropower transistor amplifier and then fed to an ultra low power voltage comparator . . . Hobby Circuit designed by David Johnson P.E.-July, 2009

Power Amplifier Clipping Indicator -  At some stage, we will all find ourselves pushing hi-fi equipment just a little too hard, and if lucky, will just find that the sound has become "dirty".  If this happens too often or is too severe, tweeters are the first to gothey are damaged by the excessive power generated by a combination of "power compression" and the harmonics created when an amplifier clips.  The same may well happen to one's ears, but the effect is much more subtle  (and cannot be fixed !) .   __ Designed by Rod Elliott  ESP

Power Indicator for the Water Softener -  This power indicator circuit is intended to be used as an extension for the water softener.  It might be easier to just place a LED but it is better to make a rectifier that detects the presence of the 15 kHz signal generated by the 555 IC.  Water Softener Power Indicator Schematic The rectifier is connected at the water __ Designed by Popescu Marian

Power Loss Indicator -  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

Programmable LED indicator -  This circuit uses CD4017 to program a bicolour LED in ten different modes with combinations of red and green.   __ 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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