Hobby Circuits designed by Dave Johnson

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


Text & Graphics Copyright © David A. Johnson, PE  --  ALL Rights Reserved.
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Indicate DC Current Flow

Indicates Automotive Electrical Voltage

Knocking rings Doorbell

Medical_Corona_Monitor

Modified LED Night Light

Modified Shake to Charge Flashlight

NMH/NiCd 6v Battery Tester

Ocean Wave Power Generator Demo Unit

One-Watt White LED Night Light

Optical Filter using Color Film Negative

Scare Off Pigeons

Security_Gate_Power_Source

Shadow Activated Motion Detector

Slotted Opto-Sensor used in Honeybee Counter

Sound Generator-Clicking

Telescope_Coin_Operated

Tester 4-20ma Current Loop

Touch Alarm for Door Knob

Touch Switch controls a 120 VAC load

Use Color Film Negative to Make an Optical Filter

14v LED AuxiliaryLamp with a 60 Watt Lamp

1Khz to Over 70Mhz Light Receiver

1us LED Pulse Driver + Voltage to Frequency Converter

1W White LED Night Light

Basement Remote Doorbell

Cheap Close-Up Camera Lens

CT Hour Meter

Demo of a Wave Power Generator System

Doorbell heard in Basement

DVD Recorder + TV Camera Make Cheap Data Logger

Earthquake Alarm Circuit

Harvest Earthworms with this Electrical Device

Homemade Corner Cube Reflector