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Circuits designed by David Johnson, P.E.
Last Updated on: Friday, December 29, 2017 02:53 AM

List of Dave's Circuit Designs

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

Testers / Monitors Circuits
Circuits Designed by Dave Johnson, P.E. :

Indicates when it is Time to Dust

Inductor Self-Resonance Tester

Is it Time to Dust?

Isolated AC Current Monitor

Isolation Transformer Circuits

Laser Diode Tester

Laser/LED Light Output Intensity Meter

Lead-Acid Battery Low Voltage Indicator

Light Receiver Works from 1Khz to Over 70Mhz

Low Power Amp Monitors Light

Low Value Capacitance Meter

Low Voltage 120vAC Power Line Alarm

Medical Fluid Detector

Modulated Light Monitor #1

Monitor Clear Fluids

On/Off Flip/Flop Circuit with Automatic Timeout

One Shot (D-Flip/Flop) Circuit

Optical Fiber Pressure & Motion Test

Optical RFID Test Circuit

Piezoelectric Vibration Sensor Activates Switch

Pot Controlled Variable LED Intensity Circuit

Power Line Alarm

Power Loss Beeper

Power Reminder Beeper

Precision AC Peak Detector

Pulsed LED Test Circuit

Pushbutton Oneshot & Latch

Resistance Tester got UL Ground Requirement

RS232 Data Bus Status Monitor

Self-Powered AC Current Indicator

Serial Data Bus Status Monitor

Shadow activated (or hand wave) Motion Detector

Single Lead-Acid Cell Voltage Monitor

Solar Insolution Meter

Solar Path Light Improvement

Solar PV Cell Test Fixture

Solar-Powered Pump Motor Controller

Temperature Sensor MOSFET

Temperature Sensor with 4 to 20ma Current Loop

Test UL Ground Resistance

Tester for Brown Out Voltage

UL Ground Resistance Tester

Ultra Low Power Human Finger Detector

Under/Over Voltage Alarm on AC Line

Unplugged Power Cord Alarm

Water Cistern Level Alarm

Water Flowing in Pipe Indicator

Water Heater Flame Detector

White LED Lifetime Tests

Well Pump Flasher & Beeper

White LED is Powered By One Nimh Cell

Water Seepage Monitor

X100 Scope Probe

120VAC Under Voltage Tester

12v Cooling Fan Thermostat

12v Lamp Current Indicator

20ma Current Loop Tester

20Mhz VCSEL 3mw Laser Test Circuit

36-Hour Watchdog Timer

40Khz Laser Burst Detector

40Khz LED Test Signal Generator

40KHz Light Receiver Front-End Circuit

6v NMH/NiCd Battery Tester

AC Current Controls Hour Meter

AC Current Test Source

AC Power Line High/Low Voltage Tester

Acceptable Voltage Indictor

Alarm sounds when Water is Detected

Alternating CW & CCW Motor Driver

Audio Frequency Digital Noise Generator

Bad Light Bulb Indicator

Button Battery Cell Internal Resistance Measurement Circuit

Caps Provide Voltage Boost to Series Regulator

Circuit Forms Divide By 1.5 Counter

Clear Fluid Detector #2

CMOS Logic Inverter Amplifier Characteristics

Corona Monitor

Current Indicator for Battery Chargers

Current Injector

Delayed Pulse Generator

D-Flip/Flop One Shot Circuit

Does Power Line have 120 VAC or 240 VAC?

Either indicates 120 VAC or 240 VAC

Electric Field Disturbance Monitor-Alarm Discriminator + Battery Monitor

Electric Field Disturbance Monitor-Front End + Power Supply Circuit

Electrical Current Indicator

Electrodeless Water Level Monitor

Energy Harvesting using a Current Transformer

Expanded Scale 12v Battery Voltage Monitor

Fireplace Fizzle

Fluid Level Monitor

Freezing Temperature Alarm

Full Wave Rectifier

High-speed 75MHz light receiver

Honeybee Counter

Human Traffic Footstep Detector Preamp


Dave's Circuits

Hobby Circuits

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


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