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Hobby Circuits designed by Dave Johnson

Last Updated on: Tuesday, October 24, 2017 03:04 PM

Text & Graphics Copyright © David A. Johnson, PE  --  ALL Rights Reserved.
LINKING to Dave's circuits is permitted but COPYING CONTENT to your WEB SITE server IS NOT!

Indicator Circuits
Circuits Designed by David Johnson, P.E. :

Fake Car Alarm Light

Flashing LED Power Indicator

Flashing Light to simulate Car Alarm

Four Line Telephone Line Status Indicator

Front Desk Service Beeper

High DC Current Indicator

High Intensity Line Powered LED Flasher

Hot AC Power Line Indicator

Indicate DC Current Flow

Indicates 120 VAC or 240 VAC

Indicates Automotive Electrical Voltage

Indicates Battery Charge Current

Indicates Battery Charging Current

Indicator for Acceptable Voltage

Indicator for Bad Light Bulb

IR Remote LED Indicator Light

Lead-Acid Battery Low Voltage Indicator

LED Flasher needs only 1.5 VOLTS

Line Powered High Intensity LED Flasher

Line Status Indicator for 1 Telephone Line

Low Battery Voltage Flasher

Low Current Flashing LED Power Indicator

Low Power LED Flasher

Low Voltage Indicator for Lead-Acid Battery

Moving AIR Indicator

One-Line Telephone Line Status Indicator

Piezoelectric Water Flowing Indicator

Ramping Lamp Driver

Remote LED Indicator Light

RFID Smart Key Detector

RS232 Data Bus Status Monitor

RS-232 Serial Interface Status Indicator Circuit

Self-Powered AC Current Indicator

Serial Data Bus Status Monitor

Telephone Status Indicator for 4 Lines

Three-Volt Low Battery Voltage Flasher

Transmit to a Remote LED Indictor Light

Two Line Telephone Line Status Indicator

Two Transistor Oscillators

Two-Transistor Low Power Oscillators

Ultra Low Power Detects Clear Fluid

Version 4 of a DC Current Indicator

Version a of 1.5v LED Flasher

Water Flowing in Pipe Indicator

Wireless LED Flasher

Wireless RFID Smart Key Detector

1 Line Telephone Line Status Indicator

1.5v LED Flasher Version A

120 VAC / 240 VAC Indicator

125khz Wireless Smart Key Detector

12v Lamp Current Indicator

12v Touch Switch Exciter Circuit

1uS Light Pulse Receiver + Post Amp

2 Line Telephone Line Status Indicator

2 Transistor Oscillators

3 Volt Low Battery Voltage Flasher

36-Hour Watchdog Timer

4 Line Telephone Line Status Indicator

AC Current Indicator Light

AC Indicator-Self Powered

Acceptable Voltage Indictor

Active AC Power Line Indicator

Alarm Beeps when the “Check Engine” Light Turns On

Alkaline Low Battery Voltage Indicator

Automotive Electrical Voltage Indicator

Bad Light Bulb Indicator

Battery Charge Current Indicator

Beeper indicates Check Engine

Bidirectional DC Current Indicator

Call-for-Service Beeper

Check Engine Beeper

Check Engine Beeper

Chicken Coop Door Opener with Timer

Circuit Indicates Battery Charge Current

Circuit Monitors 12v Lamp Current

Classic Plus & Minus DC Power Supply

Clear Fluid Detector #2


Current Indicator for Battery Chargers

DC Current Bidirectional Indicator

DC Current Indicator #4

DC Current Indicator 6

Detects Xenon Lamp Flash

Does Power Line have 120 VAC or 240 VAC?

Either indicates 120 VAC or 240 VAC

Electrical Current Indicator

Hobby Circuits by Category

  David A. Johnson, P.E. about these circuits


Imagineering Ezine    Discover Solar Energy Dave Johnson & Associates Faraday Touch Switches

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