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Last Updated: December 01, 2017 05:11 AM


Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

Circuits Designed by Dave Johnson, P.E. :

120 VAC Touch Switch  -  This is a capacitance based touch on/touch off switch, which can control power to a 200 watt 120vac load . . . Circuit by David A. Johnson P.E.-July 11, 2006

14v LED AuxiliaryLamp with a 60 Watt Lamp  -  This circuit controls power to a standard 60 watt lamp plus generates an auxiliary 14v DC supply which can power an automotive style 12 LED array . . . Hobby Circuit designed by David A. Johnson P.E.-June 27, 2000

1Khz to Over 70Mhz Light Receiver  -  This circuit uses one tiny C-MOS inverter IC to form a modulated light receiver with a very fast response.  It is designed around a PIN photo diode that is packaged for use with plastic optical fibers.  It can be used as an optical fiber receiver.  By using the open end of the optical fiber it can "sniff" out any modulated light signals . . . Hobby Circuit designed by David A. Johnson P.E.-June 11, 2000

1us LED Pulse Driver + Voltage to Frequency Converter  -  This circuit receives the signal from the above amplifier and launches powerful 1uS infrared light pulses from a low cost LED that are frequency modulated by the audio information.  The 10KHz center frequency of the pulse stream is low enough so a standard . . . Hobby Circuit designed by David A. Johnson P.E.-March 22, 1999

1W White LED Night Light  -  As many of you know, I have a pet peeve with poorly made LED night lights.  Often, the light from the LED quickly fades, so within months, the light is useless.  I have posted several versions of modified night lights using higher quality components.  This circuit is yet another version, which produces much more light than those other designs.   . . . Hobby Circuit designed by David A. Johnson P.E.-November 06, 2008

4-20ma Current Loop Tester  -  This circuit injects an adjustable current through a wire loop.  Using a digital current meter, the current can be adjusted from near zero to over 24 milliamps . . . Circuit by David A. Johnson P.E.-November 03, 2004

60 Watt Lamp with Auxiliary 14v LED Lamp  -  This circuit controls power to a standard 60 watt lamp plus generates an auxiliary 14v DC supply which can power an automotive style 12 LED array . . . Circuit by David A. Johnson P.E.-June 27, 2000

6v NMH/NiCd Battery Tester  -  I designed this circuit to test rechargeable six volt battery packs under constant current conditions.  As designed, the circuit applies a 10 amp load to the battery pack.  A heat sink must be used on the main power transistor . . . Circuit by David Johnson P.E.-December 12, 2004

"Ball" Lightning in a jar? -  Schematic + Info + pictures __ Designed by Lennie Zink

"I See Dead Pumpkins" -  11-Oct-04 -Design News:   There's no better Halloween prop than a carved pumpkin.  But Mark didn't like the idea of leaving burning candles unattended in his squash, so he built a battery-powered light source instead.  For a realistic effect, he used a timer circuit that produces a pseudo-random timer pattern that makes two __ Gadget Freak

10 Channel Light Controller -  A 10 channel light controller using PWM/ up to 1a per channel at 12v __ Contact: P. Townshend EduTek Ltd

120 VAC Touch Switch -  This is a capacitance based touch on/touch off switch, which can control power to a 200 watt 120vac load. . . Circuit by David A. Johnson P.E.-July, 2006

14v LED AuxiliaryLamp with a 60 Watt Lamp -  This circuit controls power to a standard 60 watt lamp plus generates an auxiliary 14v DC supply which can power an automotive style 12 LED array . . . Hobby Circuit designed by David A. Johnson P.E.-July, 2006

1Khz to Over 70Mhz Light Receiver -  This circuit uses one tiny C-MOS inverter IC to form a modulated light receiver with a very fast response.  It is designed around a PIN photo diode that is packaged for use with plastic optical fibers.  It can be used as an optical fiber receiver.  By using the open end of the optical fiber it can "sniff" out any modulated light signals . . . Hobby Circuit designed by David A. Johnson P.E.-June, 2000

1us LED Pulse Driver + Voltage to Frequency Converter -  This circuit receives the signal from the above amplifier and launches powerful 1uS infrared light pulses from a low cost LED that are frequency modulated by the audio information.  The 10KHz center frequency of the pulse stream is low enough so a standard . . . Hobby Circuit designed by David A. Johnson P.E.-March, 1999

1W White LED Night Light -  As many of you know, I have a pet peeve with poorly made LED night lights.  Often, the light from the LED quickly fades, so within months, the light is useless.  I have posted several versions of modified night lights using higher quality components.  This circuit is yet another version, which produces much more light than those other designs. . . . Hobby Circuit designed by David A. Johnson P.E.-November, 2008

2-wire Game Show Time -  Several Game Show timers included, scroll to find this one.  The game show timer determines which contestant presses their button first by lighting a lamp and ringing a bell and the slower  contestants are locked out.  The circuit is convenient in that only two wires are needed to interconnect the stations and the wires may all go back to the base unit or they may be "daisy-chained" between stations.  There is no electronic limit on the number of stations.  The circuit uses a 24 volt power source and 12 volt lamps when built as shown but the experienced experimenter may scale these voltages along with the zener voltages if desired.  If the SCR triggers when the power is applied or when the reset button is pressed, add a 0.1uF capacitor from anode to cathode.     (A sudden increase in voltage across some SCRs can trigger them, especially if the gate impedance is high.)  __ Contact: Charles Wenzel of Wenzel Associates, Inc.

3-up Decision maker -  This electronic device will help you make important decisions    (or not) .  While it is deciding the solution to your problem it will convince you how difficult it really is by a painful growling noiseor maybe this is normal when you have to think!__ CdS Electronic

4-20ma Current Loop Tester -  This circuit injects an adjustable current through a wire loop.  Using a digital current meter, the current can be adjusted from near zero to over 24 milliamps. . . Circuit by David A. Johnson P.E.-May, 2012

5-Finger LED Counter -  Our FIVERP5 has many applications; Teach your children how to count to five! Draw attention and a smile.  Press the push button five times and trigger your hobby rocket, etc.  The unique small design will allow you to mount it almost anywhere.  Operate it with 9V battery, 12V car battery, four 1.5V batteries, or via one of our battery simulator kits.  The alternative uses are endless.   __ Contact: Kit from Elich Industrial Development, Corp

60 Watt Lamp with Auxiliary 14v LED Lamp -  This circuit controls power to a standard 60 watt lamp plus generates an auxiliary 14v DC supply which can power an automotive style 12 LED array. . . Circuit by David A. Johnson P.E.-July, 2006

6v NMH/NiCd Battery Tester -  I designed this circuit to test rechargeable six volt battery packs under constant current conditions.  As designed, the circuit applies a 10 amp load to the battery pack.  A heat sink must be used on the main power transistor. . . Circuit by David Johnson P.E.-December, 2004

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Gadgets:  #'s - C        D - E        G - L        M - O        P - S        T - Z


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