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Hobby Circuits designed by Dave Johnson

Last Updated on: Tuesday, June 01, 2021 03:22 PM

List of Hobby Circuit Designs

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

Micro Power Circuits
Circuits designed by David Johnson, P.E. :

LED Flasher that is Battery Free

LED Flasher-Wireless Circuit

Line Status Indicator for 1 Telephone Line

LM317 adjustable voltage regulator used in Battery Eliminator Circuit

Low Power LED Flasher

Momentary Touch Activated Switch

Oscillator Draws 2 Nanoamps

Over-Temperature Micro-Power Alarm

Piezoelectric Device used for Motion Alarm

Pulse Generator uses Micropower


Replace a Pushbutton Switch with this Infrared Safety Switch

Shadow Activated Motion Detector

Slotted-Type Optical Interrupter Draws Microamps

SSR Requires Ultra Low Control Current

Tester for Modulated Light

Three-Volt Low Battery Voltage Flasher

Three-Volt Powered Very Loud Beeper

Touch Alarm for Door Knob

Transistor-Switch Detects Audio Signal

Two-Transistor Low Power Oscillators

Ultra Low Power 32Khz Crystal Oscillator

Ultra Low Power LED Flasher

Universal Flasher using a Latching Relay

Very Low Voltage Oscillator Circuit

Voltage Limiting with a Supercapacitor

Voltage Monitor for a 9v Battery

Watt-Hour Meter Monitor

Wire Loop Security Alarm

40Khz Burst Laser Diode Driver

40KHz Light Detector with Sunlight Immunity

50ua Current Drives Solid State Relay Requires Only

Alarm Sounds At Freezing Temperatures

Basement Remote Doorbell

Battery-Powered Freezer Alarm

Battery-Powered LED Flashing Advertising #2

Capacitance Touch Switch

Cheap Low Power 3v 2hz Oscillator

Circuit Eliminates 9v Battery


CMOS Oscillator, Draws Only 0.5ua

Detector/Switch for Audio Signal

Exciter Circuit-12v Touch Switch

Flashing LED Advertising Badge #1

High Ambient Light Immunity with a 40Khz Light Detector

High Temperature Thermocouple activates Relay

Highly Stable Lower Power Oscillator

Hour Meter triggered by Machine Vibration

Indicates Battery Charge Current

Knocking rings Doorbell

LED Flasher needs only 1.5 VOLTS


Hobby Circuits by Category

Dave's Circuits

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


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