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Last Updated: December 07, 2017 02:04 PM

Circuits Designed by Dave Johnson, P.E.

Classic Linear 5v Supply using 6.3VAC TransformerThere are times when you wish to control a pulse width modulation (PWM) signal with a DC voltage, ranging from 0v to 5v.  This voltage is often created by a computer interface.  The circuit below performs this voltage to PWM conversion.  PWM signals are often . . . Hobby Circuit designed by David Johnson P.E.-October, 2010

Closet Light with Automatic 3-Minute TimeoutThe circuit below is powered by three 1.5v alkaline AA cells.  With a finger tap to the pushbutton trigger switch, a cluster of 6 wide angle white LEDs is turned on.  The lights remain on for about 3 minutes, then will turn off.  The circuit’s standby current is only a few microamps.  A set of fresh batteries should last at least 200 light applications.  The circuit uses a Schmitt trigger inverter and two transistors.  When the pushbutton switch S1 is pressed, the 10uF capacitor C1 is discharged. . . Circuit by David Johnson P.E.-November, 2010

CMOS IC Flashes LEDJudging from the numerous references I have received, this electronic circuit, hobby circuit seems to be rather popular.  Many published circuits which flash LEDs need 3 or more volts.  This electronic circuit uses only a single inexpensive C-MOS IC and . . . Hobby Circuit designed by Dave Johnson P.E.-June, 2000

Computer Controlled PWM CircuitThere are times when you wish to control a pulse width modulation (PWM) signal with a DC voltage, ranging from 0v to 5v.  This voltage is often created by a computer interface.  The circuit below performs this voltage to PWM conversion.  PWM signals are often. . . Circuit by David A. Johnson P.E.-October, 2010




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

Classic Linear 5v Supply using 6.3VAC Transformer -  There are times when you wish to control a pulse width modulation (PWM) signal with a DC voltage, ranging from 0v to 5v.  This voltage is often created by a computer interface.  The circuit below performs this voltage to PWM conversion.  PWM signals are often . . . Hobby Circuit designed by David Johnson P.E.-October, 2010

Clock Controller using AT89C2051 1 -  The Clock Controller V1.1was designed to be an exemplary of using 'C' language to control timer0interrupt, 7-segment LED and keypad scanning.  It provides 1-bit sink currentdriving output, for driving a relay, opto-TRIAC, say.  Many projects requiring7-segment display and keypad interfacing may get the idea from the Clockcircuit and software.   __ Designed by Wichit Sirichote

Closed Loop Flow Control Manages ATM Channel Bandwidth -  11/21/96 EDN-Design Ideas Using closed-loop flow control, you can keep the ATM data pipe wide as well as manage it efficiently.  A primer in closed-loop flow control and the related ICs will help you implement this control scheme in your next ATM design. __ Circuit Design by David Copeland, Texas Instruments Inc.

Closet Light with Automatic 3-Minute Timeout -  The circuit below is powered by three 1.5v alkaline AA cells.  With a finger tap to the pushbutton trigger switch, a cluster of 6 wide angle white LEDs is turned on.  The lights remain on for about 3 minutes, then will turn off.  The circuit’s standby current is only a few microamps.  A set of fresh batteries should last at least 200 light applications.  The circuit uses a Schmitt trigger inverter and two transistors.  When the pushbutton switch S1 is pressed, the 10uF capacitor C1 is discharged. . . Circuit by David Johnson P.E.-November, 2010

CMOS Gate Implements Reverse Phase Control -  05/21/98 EDN-Design Ideas (File has seeveral  circuits, scroll down) The circuit in Figure 1 implements a "reverse" phase control, using only a single CMOS 4001 quad NOR gate.  The circuit is known as a reverse phase control because, unlike with common TRIAC or SCR controls, conduction begins at the zero crossing of the ac sine wave.  Timing of the turn-off point __ Circuit Design by JC Johnson, Lithonia Lighting, Decatur, GA

CMOS IC Flashes LED -  Judging from the numerous references I have received, this electronic circuit, hobby circuit seems to be rather popular.  Many published circuits which flash LEDs need 3 or more volts.  This electronic circuit uses only a single inexpensive C-MOS IC and . . . Hobby Circuit designed by Dave Johnson P.E.-June, 2000

CMOS Toggle Flip Flop using Push Button -  The circuit below uses a CMOS dual D flip flop (CD4013) to toggle a relay or other load with a momentary push button.  Several push buttons can be wired in parallel to control the relay from multiple locations.  A high level from the push button is coupled to the set line through a small (0.1uF) capacitor.  The high level from the Q output __ Designed by Bill Bowden

CMOS -NAND Gates Control Sump Pump -  05/14/09  EDN-Design Ideas A similar circuit lets you control both the sump pump and the water level __ Circuit Design by V Gopalakrishnan, Indira Gandhi Center for Atomic Research, Kalpakkam, India

CNC Router -  Now this was an interesting project.  

CO2 Controller for planted tanks -  Schematic only, no description __ Designed by Jim Hurley

Cold Activated Switch -  The thermistor used has a resistance of 15k at 25 degrees and 45k at 0 degrees celsius.  A suitable bead type thermistor is found in the Maplin catalogue.  The 100k pot allows this circuit to trigger over a wide range of temperatures.  A slight amount of hysteresis is provided by inclusion of the 270k resistor.  This prevents relay chatter when temperature is near the switching threshold of this circuit __ Designed by Andy Collison

Color Organ -  This is a simple, one lamp colour organ.  It is far less complicated then the Three Channel Colour Organ.  It is simply a lamp controlled by an SCR.  It can be built in a few minutes, and combined with other circuits to make some pretty neat effects.   __ Designed by Aaron Cake

Color Organ -  PIC Project  This unit uses a PIC16F84 with an 8 bit A/D.    The signal from both stereo channels is combined and digitized.    Each of 5 frequency bands is processed using a 16 point FFT.    Then the level of each channel is output as PWM (pulse width modulation) to a set of solid state relays __ Designed by Luhan MonatMesa Arizona

Color Organ -  Schematic + Info + pictures __ Designed by Lennie Zink

Colour (Sound) Organ -  This is a simple, one lamp colour organ.  It is far less complicated then the Three Channel Colour Organ.  It is simply a lamp controlled by an SCR.  It can be built in a few minutes, and combined with other circuits to make some pretty neat effects.   __ Designed by Aaron Cake

Colour Sensor -  Colour sensor is an interesting project for hobbyists.  The circuit can sense eight colours, i.  e.  blue, green and red (primary colours) ; magenta, yellow and cyan (secondary colours) ; and black and white.  The circuit is based on the fundamentals of optics and digital electronics.  The object whose colour is required to be detected should be placed in front of the system.  The light rays reflected from the object will fall on the three convex lenses which are fixed in front of the three LDRs.  The convex lenses are used to converge light rays.  This helps to increase the sensitivity of

Common Ground 3 Channel Color Organ for a Car -  An Active Filter Design.   __ Designed by G.L. Chemelec

Common HOT 3 Channel Color Organ for a Car -  An Active Filter Design.   __ Designed by G.L. Chemelec

Comparator adds current limit to V2 controller -  05/21/98 EDN-Design Ideas -  (File has several  circuits, scroll down) Many step-down controllers satisfy the need for generating low voltages for µPs and logic.  The lower the output voltage, the greater the importance of building a system with fast transient response.  Some new controllers use the V2 control architecture, which provIdeas several speed improvements over. __ Circuit Design by Dimitry Goder, Switch Power Inc, Campbell, CA

Compensate for Optocoupler Temperature Coefficient -  11/22/01  EDN-Design Ideas When using an optocoupler in a linear application, you should consider its gain drift with temperature.  Traditional single- and dual-transistor-output devices have a notable gain drift with temperature.  In recent years, some temper __ Circuit Design by J Michael Zias, Acme Electric Corp, Cuba, NY

Compensate for wiring losses with remote sensing -  11/18/10  EDN Technical Article: By multiplexing a small ac signal on the power wires, you can infer wiring losses.   __ Circuit Design by Jim Williams, EDN's most revered contributor, passed away in June 2011 after a stroke.  He was 63.

Complete 12V Automotive Undervoltage, Overvoltage & Reverse-Supply Protection -  The LTC4365 is a unique solution that elegantly and robustly protects sensitive circuits from unpredictably high or negative supply voltages.  The LTC4365 blocks positive voltages as high as 60V and negative voltages as low as –40V.  Only voltages in the safe operating supply range are passed along to the load.  The only external__ Linear Technology/Analog Devices App Note, Sep 19th 2011

Composite Amplifiers -  Linear Technology AN21 __ Designed by Jim WilliamsJul 1st, 1986

Computer controlled infrared remote control transmitter -  Control all your devices from the PC.  This infrared remote control transmitter can be controlled from a computer.  It speaks many different remote control formats, like the Philips RC-5 standard and can be tailored to other specific types.   __ Designed by Peter Jakab

Computer Controlled Model Train Set -  I had two objectives in starting this mini project.  One was to help me get a better understanding of using a PC for control and automation.  The other was to make my younger brother’s train set a little less boring.  I never could __ Designed by Submitted Jane L, Northampton

Computer Controlled PWM Circuit -  There are times when you wish to control a pulse width modulation (PWM) signal with a DC voltage, ranging from 0v to 5v.  This voltage is often created by a computer interface.  The circuit below performs this voltage to PWM conversion.  PWM signals are often. . . Circuit by David A. Johnson P.E.-October, 2010

Computer Voltage & Temperature Monitoring -  The LTC2991 is used to monitor system temperatures, voltages and currents.  Through the I2C serial interface, the eight monitors can individually measure supply voltages and can be paired for differential measurements of current sense resistors or temperature sensing transistors.  Additional measurements include internal temperature __ Linear Technology/Analog Devices App Note, Sep 7th 2011

Computerized Infrared Remote -  control your stereo, TV and VCR from Windows, includes schematic and software

Connecting a Servo to a PICAXE -  The three simple routines below go further than the PICAXE manual.  The programs are self explanatory. __ Designed by Lewis Loflin

Constant Temperature -  This circuit is a generic low power temperature controller that can be used for stabilizing temperature sensitive electronic circuits.  It was built to stabilize a radio frequency VFO (Variable Frequency Oscillator) for ham radio applications.  The circuit has also been used to lower the drift of a Ramsey FM10a micropower FM transmitter __ Designed by G. Forrest Cook

Continuity buzzer is frugal with power -  04/15/99  EDN-Design Ideas (contains several designs, scroll to find this one)   The continuity detector in Figure 1 is based on W Dijkstra's "Fleapower circuit detects short circuits" (EDN, July 2, 1998, pg 122).  The buzzer indicator allows you to devote full attention to making the connection without having to observe an LED.  The circuit also consumes less power than Dijkstra's circuit.  Power comes from two AA or AAA cells, which last for a period equal to their shelf life.  Current consumption is less than 2.5 mA when the circuit detects continuity and less than 1.7 mA for an open circuit.  Open-circuit voltage is less than 100 mV, and short-circuit current is less than 1 mA.   __ Circuit Design by Hans Krobath, EEC, Nesconset, NY

Continuity Tester -  This circuit will detect low resistances and high resistances to produce a tone from the speaker.  It will detect up to 200k and the circuit automatically turns off when the probes are not used.  __ 555-Timer

Continuity Tester -  This circuit senses only dead shorts on a populated board.  It will not ring through or damage components.  It shuts off when not in use.  It was first published in Electronics magazine, June 21, 1979 45 __ Designed by Andrew R. Morris

Continuity Tester -  Among the essentials for circuit design and prototyping is the continuity tester, a simple device which provides an audible indication when a sufficiently low resistance is applied between its input probes.  This version has a feature which automatically turns off the tester after about two minutes, thereby saving the 9 volt battery from inadvertent discharge.  The tester produces a high-pitch tone when less than 10 ohms is placed between the input probes.  The 10 ohm threshold is a convenient value that indicates hard-wired paths, but excludes indications for circuit paths through most components.  In addition, the amount of current presented to the circuit by this __ Designed by Arthur Harrison

Continuity Tester -  Occasionally you need a continuity test between two points in an electronic circuit.  Unfortunately, most continuity testers are prone to "lie".  They don't do that deliberately, but if they see a small resistance, they still tell you that you have continuity.  They just don't know any better __ Designed by Tony van Roon  VA3AVR

Continuity Tester Fits Into Shirt Pocket -  10-Jan-08 EDN-Design Ideas A pocket-sized continuity tester responds quickly to shorts or opens and is protected against connection to a live circuit __ Circuit Design by Tom Wason, Phoenixville, PA

Continuity Tester Latching -  A continuity tester is a must on every service bench for testing cables, pc-boards, switches, motors, plugs, jacks, relays, and many other kinds of components.  But there are times when a simple continuity test (or your multi-meter) doesn't tell the whole story.  For example, vibration-induced problems in automobile wiring can be extremely difficult to detect because a short or open is not maintained long enough for a non-latching tester to respond __ Designed by Tony van Roon  VA3AVR

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