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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...(circuit / schematic design added 6/06) |
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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 caused me to leave the garage light on overnight
many times until I created this solution. I have outdoor lights....Designed by Andrew
R. Morris (added 09/05) |
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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…
….(designed by David A. Johnson) |
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Hot Water Tank Indicator - (schematic / circuit design added 9/02) |
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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....(circuit added
09/08) |
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Incoming call indicator - (circuit added 06/07/08) |
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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 answer: pass
or fail. Usually, two indicators assume this role: green for pass and red for fail. In
most applications, a sensor transforms the tested parameter to a voltage; the test
fixture.....(design idea added 1/05) |
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Indicator has Electronic Lens - 09/04/03 EDN-Design Ideas: The method for
implementing an extended-scale meter described in an earlier Design Idea 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.....(design
idea added 6/06) |
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Indicator LED Bus - This document describes the connection of the Indicator LED
Bus to compatible displays and includes example code for a BASIC Stamp and LCDC
examples. (added 6/06) |
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Isolated indicator signals telephone line's status - 06/08/06 EDN-Design Ideas:
Micropowered circuit shows off-hook phone.....(design idea added 11/06) |
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LED Battery Condition Indicator - (circuit / schematic design added 6/06) |
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LED Flasher Indicates Low Battery Condition - 01/02/97 EDN-Design Ideas: (design
idea added 5/02) |
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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. (circuits added 09/05) |
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Level indicator with 10 LED - (schematic / circuit added 2/07) |
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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 an idle line for a couple minutes before
expecting it to work. A high-brightness LED is recommended. (added 1/08) |
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Low Battery Indicator - Files contains several circuits: LED flasher, silent
metronome, low battery indicator, high voltage generator (added 7/03) |
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Low Battery Indicator has High Efficiency - 05/03/01 EDN-Design Ideas:.....(design
idea added 11/05) |
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Low Battery Indicator uses Fleapower - 09/04/03 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 little more than a year. Battery-powered devices that need to
run continuously for a long time require battery indicators that consume minimal
power.....(design idea added 10/03) |
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Mains Voltage Indicator - The solidstate voltmeter circuit described here
indicates the mains voltage with a resolution that is comparable to that of a
general-purpose analogue voltmeter. The status of the mains voltage is available in
the form of an LED bar graph.....(electronic Circuit / Schematic added 10/04) |
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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 flashing is stopped when the phone is picked up.
Designed by Andrew R. Morris (added 6/06) |
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Model Aeroplane Navigation Strobe/Battery Level Indicator - Fair Waring, site
contains annoying popups. 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 ....(design added 5/05) |
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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 some distance away from the fan. I scratched
my head a bit.... ….(designed by David A. Johnson) |
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Multi-Switch Doorbell with Indicators - (circuit / schematic design added 6/06) |
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Off Hook Phone Line Supplies 150 MW - 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.....(design idea
added 6/06) |
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OpAmp Rectifier Signals Input State - 07/21/94 EDN-Design Ideas: The op-amp
rectifier in Fig 1 operates from a single supply and provides 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.....(design idea added 3/03) |
