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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. . . . [© EFY Enterprises Pvt. Ltd. All rights reserved.]
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. . .
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. . . [Electronic communications to r dot p at 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.,
08/16/06]
Multi-Switch Doorbell with Indicators - . . .
Octuple Infrared Proximity Detectors
Circuit - 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 find this one. . . . [from Rob Paisley's Model Train web site]
Off-Hook Phone Line Supplies 150 mW - 09/01/94 EDN Design Idea 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. . . [by Ron Clark and Bob Underwood, Maxim Integrated Products,
Sunnyvale, CA]
One LED Indicates Two Power States - 12/05/96 EDN Design Idea Uses a single bicolor LED to indicate both power-on and
blown-fuse conditions. . . [by Jim Hagerman, Hagerman Technology, San Diego, CA]
One-Line Telephone Line
Status Indicator - This circuit monitors one phone
line . . . [Circuit by David A. Johnson P.E., 06/10/00]
Op-Amp Rectifier Signals Input State - 07/21/94 EDN Design Idea 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 . . . [by Dan Stiurca, Gh Asachi Technical University, Iasi,
Romania]
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. . . . [© EFY Enterprises Pvt. Ltd. All rights reserved.]
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 the temperature of the pipe goes above certain limit, it flashes an LED. . . .
[© EFY Enterprises Pvt. Ltd. All rights reserved.]
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. . . . [© EFY Enterprises Pvt. Ltd. All rights reserved.]
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