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Last Updated: December 07, 2017 02:04 PM

Circuits Designed by Dave Johnson, P.E.

Capacitance Touch SwitchA single 1.5v silver oxide button cell powers this complete touch activated switch circuit for 5 years.  It features both a normally open and a normally closed set of solid state switch thermals.  It also has an adjustable sensitivity, which can be set . . . Hobby Circuit designed by David Johnson P.E.-January, 2002

characteristics of CMOS Logic Inverter AmplifiersThis chart shows some of the measured characteristics of three different unbuffered CMOS logic gates, used as voltage amplifiers . . . Hobby Circuit designed by David Johnson P.E.-February, 2002

Charge Coupled Bi-Directional Power MOSFET RelayThe circuit uses an inexpensive C-MOS inverter package and a few small capacitors to drive two power MOS transistors from a 12v to 15v supply.  Since the coupling capacitor values used to drive the FETs are small, the leakage current from the power line. . . Circuit by Dave Johnson P.E.-June, 2000




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

C# Application Controls Simple Circuit ADC -  30-Oct-08 EDN-Design Ideas Control a simple, low-cost ADC with a PC's serial port __ Circuit Design by Yury Magda, Cherkassy, Ukraine

C-52 Evb Robot Controller -  Use a C-52 EVB for simple robot experiments.  Build a simple two wheels robot with L293 H-Bridge driver and IR sensor.  Write a C program controls robot tracked with black tape.   __ Designed by Wichit Sirichote

Caboose Marker Flashing Red LED Light -  A circuit that drives a red LED from a 1.5 volt battery and simulates an incandescent light.  Duty cycle can be changed by selecting resistor values __ Designed by Dick Cappels

Calibrating the Current Offset Bias (COB) Register for the DS278x Family of Fuel Gauges -  App Note 4188  -- 3/10/2008  --    (add 5/08) __ Maxim Integrated

Camera Remote Control System using Basic Stamp -  The remote control receiver is a custom design based on a pre-built 433MHz UHF radio receiver, a decoder chip and a BASIC Stamp.  The Stamp is expensive, but easy to work with.  The receiver requires 8.5mA, plus 1.5mA for each LED   (individual or segment) that is lit for a maximum of up to 23mA.  In practice it is between 13 and 16mA.  Pressing a button onThe remote transmitter causesThe receiver to consume an extra 0.2mA.  In the 'power saving' mode the PBASIC 'nap' instruction is used in combination with turning all the LEDs off to reduce power consumption to 4mA.  The battery should last about 30 hours of on-time. __ Designed by andrew @ scss.com.au

Candle Simulator -  This PIC Project  uses a PIC to simulate the flickering of a candle entirely in software.  The brightness of the lamp is controlled by doing PWM (pulse width modulation) of the power to the lamp.  A random number generator controls the flickering amplitude.   __ Designed by Luhan Monat-Mesa Arizona

Capacitance meter bins parts -  03/24/14EDN-Design Ideas This simple, elegant circuit lets you quickly sort through capacitorsThe heart of the circuit is the RS flipflop using 4093 NAND gates along with transistors Q1 and Q2,  which discharge the reference and test capacitors respectively.  The reference capacitor (CREF) and the test capacitor (CX) are charged from zero volts, followed by a reset pulse applied to the bases of Q1 and Q2 __ Circuit Design by Raju Baddi

Capacitance Touch Switch -  A single 1.5v silver oxide button cell powers this complete touch activated switch circuit for 5 years.  It features both a normally open and a normally closed set of solid state switch thermals.  It also has an adjustable sensitivity, which can be set . . . Hobby Circuit designed by David Johnson P.E.-January, 2002

Car Fan Speed Controller -  Using this circuit you can control the speed of 12V DC fans used in cars.  The circuit is built around timer 555, which is wired as an astable multivibrator.  The output...__ Electronics Projects for You

Car Window Closer -  This circuit automatically rolls up a car’s electric windows when it rains.  The windows are rolled up one at a time while the system monitors the window motor current.  When the motor stalls, the system moves to the next window and shuts off it’s the last  __ Designed by Andrew R. Morris

Cat or Dog Detector for Pet Door -  This circuit uses one tuned coil for on the door and just a single wire loop on the animals collar.  When the two coils come close together, it produces a signal that can cause a an LED to light and also trips a solenoid to unlock the door so it can open.  Since all these doors are somewhat different, I leave __ Designed by G.L. Chemelec

CD strobe scope -  This is a strobe scope.  The disc is rotating but it looks still.   __ Designed by The Electronic Lives Manufacturing-presented Chan

Cellphone-Based Device Control with Voice Acknowledgement -  Here is a circuit that lets you operate your home appliances like lights and water pump from your office or any other remote place.  So if you forgot to switch off...__ Electronics Projects for You

Cellphone-Based Remote Controller for Water Pump -  Inconvenience in switching on a water pump installed in a remote farm is a common problem faced by farmers.  Many circuits have been developed to solve this problem.  Most of them...__ Electronics Projects for You

Cellular Phone calling Detector -  Flashes a LED when detecting an incoming call; Powered by one 1.5V cell __ Contact: Flavio Dellepiane, fladello @ tin.it

Cellular-telephone/camera-flash illumination -  05/27/04  EDN-Design Ideas Successfully implementing flash lamps involves understanding numerous practical considerations.  Next-generation cellular telephones will include high-quality photographic capabilities.  To support their improved image sensors and optics, they will need high-quality "flash" illumination, which requires special design attention.  This lighting is crucial for yielding good photographic performance and requires careful consideration.   __ Circuit Design by Jim Williams, EDN's most revered contributor, passed away in June 2011 after a stroke.  He was 63.

Celsius-to-digital thermometer works with remote sensor -  04/15/04  EDN-Design Ideas You can use a single-supply system to precisely measure the temperature at a remote location with less than 1°C error over a 0 to 100°C range (Figure 1).  The circuit includes T1, a low-cost AD590 temperature sensor; IC1, an AD8541 r __ Circuit Design by Elana Lian and Chau Tran, Analog Devices, Wilmington, MA

CFL Ballast for 26w/ Sprial Lamp 220VAC Input -  The IRPLCFL5E reference design is an electronic ballast for driving 26W compact fluorescent lamps from 220VAC.  The circuit provides all of  necessary functions for preheat, ignition and onstate operation of  lamp and also includes  EMI filter and  rectification stage.  The circuit is built around  IR2520D Ballast Control IC.  

characteristics of CMOS Logic Inverter Amplifiers -  This chart shows some of the measured characteristics of three different unbuffered CMOS logic gates, used as voltage amplifiers . . . Hobby Circuit designed by David Johnson P.E.-February, 2002

Charge Coupled Bi-Directional Power MOSFET Relay -  The circuit uses an inexpensive C-MOS inverter package and a few small capacitors to drive two power MOS transistors from a 12v to 15v supply.  Since the coupling capacitor values used to drive the FETs are small, the leakage current from the power line. . . Circuit by Dave Johnson P.E.-June, 2000

Cheap Sound Sensor for AVR -  I searched the web for a cheap method to let the ATmega respond to sound.  My knowledge in analog circuits is very limited, but what I do remember, is that you can not attach a electret mircophone to a controller pin.  The signal of __ Designed by Alexander Weber

Cheap Stepper Motor Driver -  Schematic only, no circuit description included __ Designed by Tom McQuire

Child's lamp -  Here is a mini emergency lamp that you can use as a tabletop lamp in your child’s study room.  It is battery-operated and gives sufficient light for the child to move out of the room when power fails.  The white LED in the circuit automatically turns on when light in the room goes off following a power cut.  The LED gives a flashing light instead of glowing continuously to reduce power consumption.  The circuit comprises __ Designed by D. Mohan Kumar

Chloroplast Voltage Controlled Solar Engine -  Voltage-Controlled Solar Engine: These designs are based on the Motorola MC34164-* micro power undervoltage sensing ICs.  They're pretty efficient, work at higher voltages than most solar engines, and can provide voltages for other logic circuits (say, a microprocessor).  This page hosts the original Chloroplast by Craig Maynard, as well as some Chloroplast variants by Wilf Rigter.   __ Designed by Craig Maynard

Christmas Decoration -  This project flashes 18 LEDs at three different rates and you can use these to create a Christmas decoration of your choice.  The circuit is kept simple (and cheap!) by using the 4060B IC which is a counter and oscillator (clock) in one package.  The circuit requires a 9V supply, such as a PP3 battery __ Designed by John Hewes

Christmas Lights Tester -  Like every year around the same time, I hurried to get my Christmas tree all set up and the first thing we do when the tree is 'standing' we like to hang the lights in the tree.  Okay, better first test them before putting all 50 of them in the tree.  Yep! Working beautifully.  I started a carefully planned organization of the lights so they would be evenly divided over the branches.  Now the second string of lights, tested, yep working.  In the tree with them.  Putting the plugs into the receptacle andoh no-- one series of them are on in full glory, all the others are out.  Annoyed I tried to 'fix them' by trying to push each bulb further into their sockets.  Still no go __ Designed by Jan Hamer

Christmas Star -  Christmas just would not be Christmas if you do not put a flashing star on your Christmas tree.  Here is the circuit of such a flashing star.Fig.1 shows the circuit...__ Electronics Projects for You

Christmas-Tree Lights Tester -  12/23/99 EDN-Design Ideas Why is it that you always test 48 bulbs before you find the bad one in a 50-light string? This simple circuit allows you to divide and conquer, greatly reducing the time it takes to find the bad bulb. __ Circuit Design by William Dias, Brown & Sharpe, North Kingstown, RI

Church Bell Controller -  This circuit is a church bell controller.  Basic component is an ATmega32 microcontroller.  At the circuit 2 24LC32 eeprom memories is being used, the 1st for internal standard melodies and the 2nd one is for user's compositions.  This feature will be provided in the future __ Designed by Antonis Pontikakis © 03.10.2007

Circuit Allows Long PWM Soft Starts -  02/01/07  EDN-Design Ideas Enhance timing accuracy of a switching regulator's start-up ramp __ Circuit Design by Robert N Buono, Aeolian Audio LLC, Bloomfield, NJ

Circuit Automates Switch-Over Between Battery & Source -  12/18/97 EDN-Design Ideas The use of a logic supply or an ac wall adapter can extend battery life in a small portable system by offloading the battery.  However, managing the switch-over between battery and external power can be messy.  For high-cell-count b __ Circuit Design by Len Sherman, Maxim Integrated Products, Sunnyvale, CA

Circuit Automatically Switches Off DMM -  08/17/12  EDN-Design Ideas Add automatic-shutoff to your DMM, save batteries, and eliminate wear and tear on the function switch.   __ Circuit Design by Vladimir Oleynik, Moscow, Russia

Circuit breaker handles voltages to 32V -  25-May-00 EDN-Design Ideas The simplicity of low-side current monitoring can mask the advantages of a high-side approach.  You can monitor load currents in a power supply, a motor driver, or another power circuit on either the high or the low side(ground].  However, don't let the ease of low-side monitoring cause you to overlook __ Circuit Design by Greg Sutterlin and Craig Gestler, Maxim Integrated Products, Sunnyvale, CA

Circuit Breaker Provides Overcurrent & Precise Overvoltage Protection -  7-Jun-07 EDN-Design Ideas A simple circuit breaker delivers precision overvoltage protection and overcurrent protection __ Circuit Design by Anthony H Smith, Scitech, Bedfordshire, England

Circuit Compensates 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 temperature-compensated optocouplers have appeared.  However, another option is to use two optocouplers or a dual optocoupler with appropriate feedback to make the dri __ Circuit Design by J Michael Zias, Acme Electric Corp, Cuba, NY

Circuit controls brightness of multiple displays -  05/30/02 EDN-Design Ideas I recently needed to control nine seven-segment displays for a microcontroller's serial port.  The complication I faced was the need to provide a continuous brightness adjustment for all the digits—from completely dark to fully bright.  I couldn't easily use the obvious solution of a string of 74HC595 serial-to-parallel converters driving the segments through series resistors, because I wou __ Circuit Design by Stephan Goldstein, Analog Devices, Wilmington, MA

Circuit Controls Inrush Current In AC-Operated Power Supplies -  10/06/11  EDN-Design Ideas Inrush current control circuit for ac operated power supplies.  Large power supplies that operate from ac wall voltage have large input-filter capacitors.  You must limit the inrush current to those capacitors.  Otherwise, the supply may trip the ac circuit breaker, or you may damage the rectifier, filer chokes, or PCB (printed-circuit-board) traces.  The circuit in this Design Idea inserts a current-limiting resistor in the capacitor’s charging path.   __ Circuit Design by Peter Demchenko, Vilnius, Lithuania

Circuit controls intensity of reflex optical sights -  02/21/02 EDN-Design Ideas A popular category of aiming/pointing aids is the reflex, or "red-dot," sight.  This system finds use in such diverse applications as astronomy, archery, and shooting.  In the reflex sight, light from an internal source-typically a high-intensity red LED-reflects from a curved, transparent optical(reflex] element through which you view the target __ Circuit Design by Stephen Woodward, University of North Carolina, Chapel Hill, NC

Circuit Controls Isolated 12V Stepper Motor -  09/26/96 EDN-Design Ideas -  Allows full direction and step control of a12V, four-phase stepper motor from a5V, TTL/CMOS -compatible logic controller.    __ Circuit Design by Martin O'Hara, Newport Components Ltd, Milton Keynes, UK

Circuit Controls Microneedle Etching -  27-Nov-03 EDN-Design Ideas At its invention roughly two decades ago, STM(scanning tunneling microscopy] created a sensation because it was the first technology to make atomic-scale-resolution imaging a routine procedure.  An essential requirement for the practical application of STM is some means for the reproducible fabrication of supersharp, atomic-scale needle tips __ Circuit Design by Stephen Woodward, Marine Sciences, Chapel Hill, NC

Circuit controls multiple thermoelectric coolers -  08/19/99 EDN-Design Ideas Optoelectronic and other components sometimes use a thermoelectric cooler and a thermistor for temperature control.  A typical thermoelectric cooler __ Circuit Design by Frank Effenberger

Circuit controls ratiometric or simultaneous power-up of multiple rails -  13-May-04 EDN-Design Ideas Many applications use FPGAs, ASICs, or DSP chips, which usually require multiple voltage rails, typically two  the core voltage and the I/O voltage.  The core voltage is usually lower than the I/O voltage.  Guidelines for determining how to power up two orvoltage rails depend on the part and the manufacturer you use __ Circuit Design by Dirk Gehrke, Texas Instruments, Freising, Germany

Circuit Controls Slew for Stepper Drive -  03/14/97 EDN-Design Ideas The circuit in Figure 1 provIdeas slewing control for stepper motors that you use in sophisticated applications, such as monochromator movements in optical experiments.  The LM331 VFC plays a vital role in this circuit.  The constant 10V dc from the IC9596 voltage reference routes to the VFC through the DG303 CMOS switch.  The DG303's __ Circuit Design by J Jayapandian, IGCAR, Tamil Nadu, India

Circuit controls stepper-motors -  01/08/04 EDN-Design Ideas Stepper motors are useful in many consumer, industrial, and military applications.  Some, such as personal-transportation systems, require precise speed control.  Stepper-motor controllers __ Circuit Design by Noel McNamara, Analog Devices, Limerick, Ireland

Circuit Controls Two LEDs with One Microcontroller Port Pin -  Microcontroller port pins can typically be driven either high or low, or else be put into an input or high-impedance state.  This circuit uses the three states to drive two separate LEDs with one port pin.  This can be very useful when __ Designed by Spehro Pefhany

Circuit Delivers constant power to a loA - D -  EDN-Design Ideas 07/29/2016    Here’s a novel way to supply constant power to an ill-defined load __ Circuit Design by Kiril Karagiozov

Circuit Delivers Dimming Control for White-LED Driver -  10/28/04  EDN-Design Ideas The demand for power in color cell-phone handsets is constantly increasing.  New applications steadily emerge, making it imperative to reduce power consumption in the design.  Examination of usage data shows thatthan 50% of the power __ Circuit Design by Wallace Ly, National Semiconductor, Santa Clara, CA

Circuit disconnects loA - D -  02/17/00  EDN-Design Ideas Placing a load-disconnect circuit on the output of a bootstrapped step-up regulator allows the regulator to start with load currents much higher than would otherwise be possible (Figure 1).  During shutdown, the disconnect completely isolates the battery __ Circuit Design by Larry Suppan

Circuit Disconnects Load From Battery -  03/14/96 EDN-Design Ideas To prevent battery damage, the circuit in Figure 1 disconnects the load at a predetermined level of load voltage.  This load voltage, VTRIP, is closely proportional to the battery voltage.  R1 and R2 determine the level of VTRIP  that corresponds to voltage of 1.15V at pin 3 of IC1.  A voltage of 1.15V at pin 3 of IC1 causes the internal comparator to trip.  Thus, VTRIP=1.15(R1+R2)/R1 __ Circuit Design by Michael Keagy, Maxim Integrated Products, Sunnyvale, CA

Circuit Disconnects Load From Low-Voltage Supply -  04/24/03  EDN-Design Ideas Circuit ensures safety in power-on operation.  Power supplies often include a circuit that disconnects the load when the supply voltage drops too low, such as when a battery is nearly discharged.  A p-channel MOSFET connected between supply and load is the typical approach.  However, a 1.5V single-cell battery or other low-voltage supply is insufficient to fully turn on the MOSFET.  For such low-voltage systems, consider the circuit of Figure 1.   __ Circuit Design by Steve Caldwell

Circuit Ensures Safety In Power-On Operation -  04/24/03 EDN-Design Ideas Buck converter handles battery-backup systemComputers find universal use in industrial-control systems.  During power- and start-up sequences(booting], the outputs of such control systems may yield uncontrolled pulses before the software defines the correct status.  If these outputs control the power-on state of a system, these uncontrolled pulses could have dramatic consequences __ Circuit Design by Jean-Bernard Guiot, DCS AG, Allschwil, Switzerland

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Control Circuits:   #'s - A       B - C       D - G        H - L       M - P        Q - S        T - U        V - Z


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