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AC Current Indicator Light - This circuit could be wired into a 120vac power
line, which feeds power to any load, ranging from 40 watts to 250 watts. It will
turn on a LED light whenever current is being drawn by a load. It is especially
useful for remote lights, where you may not be able to see if the lamps are receiving
power. …. [Hobby Corner Circuit by Dave Johnson] |
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AC Power Indicator - The AC powerline indicator presented here has a
complete galvanic isolation from the grid. The indicator is an LED that lights up when
a current flows, although the current can be measured more accurately with an AC
voltmeter set to its mV range.….must register on this site.... [Published in Elecktor
July/August 2010] |
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Acceptable Voltage Indictor - 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 high, low or OK. When connected
to other converters, such as a frequency to voltage converter, a current to voltage
converter or a power to voltage meter, it could provide a quick indication of a proper
level. …. [Designed by David A. Johnson] |
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AN-726: Triple-Supply Power-Good Indication with the ADM108x - AN-726 Analog
Devices Application Note.....[App Note] |
Audio Indicator - This circuit can be used to remotely monitor a
loudspeaker, alarm, or audio source for presence of an audio waveform. It can also be
directly connected across loudspeaker terminals used as a peak indicator.
….(electronic design added 6/07) |
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Audio Level Indicator - Audio Amplifier output relay delay (added 5/03)
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Audio Visual Indicator for Telephones - Many a times one needs an extra
telephone ringer in an ad joining room to know if re is an incoming call. For example,
if telephone is installed in drawing room you may need an extra ringer in
bedroom. All that needs to be done is to connect given circuit in parallel with
existing telephone lines using twin flexible wires. This circuit does not
require any external power source(added 11/06) |
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Audio Volume Indicator - uses an XS40 Board and XStend Board to display
volume of an audio input on a barograph LED. (added 5/03) |
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Automotive 12v Electrical System Voltage Indicator - This battery powered
unit is designed to quickly aid troubleshooting of 12v electrical systems in a car.
Three LEDs proved a visual indication of a +12v, ground or an open circuit voltage
level. Posted …. [Hobby Corner Circuit by Dave Johnson] |
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Automotive Electrical Voltage Indicator - This circuit will indicate if an
automotive electrical circuit has zero volts or 12 volts present. (added 7/06)
…. [Designed by David A. Johnson] |
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Automotive Speed Indicator - The speed of an automobile can be indicated by
detecting the pulses generated by the ignition system and causing an LED to light. The
circuit utilizes a quad NOR gate IC chip. Two of the gates are configured as a one
shot multivibrator… [Randy Linscott, designer] |
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Automotive Voltage Indicator - Monitors battery voltage, Three-LED Display
(circuit added 6/07) |
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Bad Light Bulb Indicator - 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. If
current is flowing to a light bulb, the circuit shunts current around a LED light,
keeping the LED turned off. If there is no current detected, the LED turns on.
The circuit should operate from 6v to 24v..... [Designed by David A. Johnson] |
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Basic Infrared Proximity Detector - The circuits on this page are for an
Infrared Proximity Detector using the Vishay Electronics TSOP4830 "IR Receiver Modules
for Remote Control Systems"….Scroll down to view all the circuits…. [from Rob
Paisley's Model Train web site] |
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Battery Charge Current Indicator - This circuit turns on a LED whenever it
detects at least 25ma of battery charge current. (added 7/06) …. [Hobby Corner
Circuit by Dave Johnson] |
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Battery Chargers Indicates Rate of Charge - 05/25/95 EDN-Design Ideas.....A
single LED indicates wher battery Chargers s delivering a trickle charge or a
fast charge, Circuit designed to charge2-14 cells.… [Design Idea by Larry Suppan,
Maxim Integrated Products, Sunnyvale, CA] |
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Battery Equal Charge Indicator - The circuit below illuminates an LED to
indicate unequal charges between two 12 volt lead batteries. It can be used to verify
that two batteries are connected in parallel or isolated since the LED will be off
when the voltages are equal within a tollerance, or on if the voltage difference is
greater than 100 millivolts. Three comparators.....(electronic schematic / circuit
added 04/03/02) |
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Battery charge indicator - Schematic only, no circuit description
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Battery Charge Current
Indicator 7
This circuit was inspired by a company needing a DC current indicator
light which was small enough to be molded into a medium size 28v rechargeable battery
assembly. They specified that they wanted the circuit to turn on the LED
indicator light with 500ma or more of battery charge current. When surface
mounted components are used, the complete assembly should be smaller than a postage
stamp. A LM4040 5 volt reference diode used both to provide a fixed 5v for the
circuit and when divided down to just 5mv, it also serves as a reference to a low
power voltage comparator......[Circuit of
the Week designed by David Johnson, P.E.] |
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Battery condition indicator12v - Schematic only, no circuit description
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Battery Monitor Emulates Auto Dashboard - 07/03/97 EDN-Design
Ideas..... When you use battery-powered scientific-recording equipment, you must know
the state of the battery, because an unnoticed battery run-down can lead to loss of
data. Several types of warning indicators are available, but all have their drawbacks.
Moving-coil indicators, test terminals, and digital flags, for example,..... [Design
Idea by TG Barnett and J Millar, University of London, UK] |
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Bi-Color LED Indicates Power/Fault - Single LED indicates both power on and
blown-fuse conditions.… [Jim Haggerman, Hagerman Technology LLC] |
Bidirectional DC
Current 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....[Circuit of the week designed by David Johnson] |
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Blown Fuse Indicator - a simple way to see if a fuse has blown without
removing it from its holder (added 4/02) |
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