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Last Updated: December 25, 2017 01:48 PM

Circuits Designed by Dave Johnson, P.E.

Pot Controlled Variable LED Intensity CircuitThe circuit below uses power from four rechargeable AA NiMH
cells to drive 3 white LEDs.  A potentiometer varies the duty cycle of a pulse width modulator circuit to vary the intensity of the LEDs from 0% to 100%.  The beauty of the circuit is that when the. . . Circuit by Dave Johnson P.E.-September, 2009

Power Line AlarmThis circuit will activate a beeper alarm whenever the AC line voltage is less than 100vac.. . . Circuit by David A. Johnson P.E.-July, 2006

Protects from Battery Polarity ReversalThis simple circuit can protect a sensitive electronic circuit from an accidental connection of a battery with a reversed polarity.  The N-channel FET connects the electronic device to the battery only when the polarity is correct.  The circuit shown was . . . Hobby Circuit designed by David Johnson P.E.-March, 2002

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

Photo Flash Charger Minimizes Parts Count -  10/22/98 EDN-Design Ideas  Photo-flash and strobe devices operate by discharging a high-voltage capacitor into a bulb.  Charging the capacitor from a battery or other low-voltage source requires a step-up DC/DC converter to boost the voltage, typically to 300V.  One way to generate the high voltage __ Circuit Design by Steven Chenetz, Micrel Semiconductor, San Jose, CA

Photoelectric-FET Optocoupler as a Linear Voltage-Controlled Potentiometer -  01/19/12 EDN-Design Ideas The circuit takes advantage of an identical photo-FET as a feedback element.  You can use a photoelectric FET as a variable resistor or a potentiometer in combination with a fixed resistor.  The H11F3M photoelectric FET has an isolation voltage of 7.5 kV, enabling you to safely control highvoltage circuit parameters.  The nonlinear-transfer characteristics of these devices are problematic, however (Figure 1).  To correct the nonlinearity, using a simple feedback mechanism as a potentiometer yields a linear response (Figure 2).   __ Circuit Design by Sajjad Haidar, University of British Columbia, Vancouver, BC, Canada

Photoflash Capacitor Charger has Fast Efficient Charging & Low-Battery Drain -  DN303 Design Notes__ Linear Technology/Analog Devices

Photovoltaic Battery Charge Controller -  A charge controller is one of the main components of a solar battery charging system (Fig.1).  Its main function is to fully charge a battery without permitting overcharge or reverse...__ Electronics Projects for You

PIC Based Motor Controller -  On these pages, I will introduce a control circuit for stepper motor.  The software of this project is adapted to Embedded Systems (Lab13) for 2002 of Cleveland State University.  PIC16F84A __ Designed by Seiichi Inoue

PIC IR/ RF Remote Control -  This is a general purpose remote control project with using programmable PIC microcontrollers (PIC16F628, PIC16F630, PIC16F684).  Schematics are shown for using infrared (IR) or radio (RF) media.  If you are not familiar with microcontroller programming, you can use fixed encoder and decoder integrated circuits instead.  Well-known such IC-s are Holtek HT-12D, HT-12E and Motorola MC145026, MC145027, MC145028.  

PIC Light Chaser -  The circuit this month is a simple 8 light chaser built around a PIC.  This will demonstrate how easy it is to program a PIC and to utilize it in a circuit.  The circuit works as follows.  When power is supplied to the circuit the PIC resets and starts.   __ Designed by Randy Linscott

PIC Micro Multiple Servo Motor Interface Using a modified version of the last program, we can control as many servomotors as we have I/O lines on port B.  In the next listing, we will control two servos in the same manner as we controlled a single servo in the previous program.  The circuit is shown in figure 4 (below).
 __ Contact: Images SI, Inc

PIC MicroController Servo Motor Interface -  In our first program , we will simply sweep the servomotor from CCW to CW and then sweep back.  The program will be kept simple as to demonstrate the priniciples of controlling a servo with a the PIC Basic language.  The schematic can be seen in figure 2 (below).
 __ Contact: Images SI, Inc

PIC plots pixels sans controller -  02/16/98 EDN-Design Ideas It is sometimes desirable to display the output of a PIC C graphically, rather than numerically.  However, the operation increases system complexity and expense.  In addition to the LCD itself, you usually need a graphics controller and at least 1 kbyte of RAM.  However, you can obtain a satisfactory plot(Figure 1) __ Circuit Design by Daryl Christopher, Juniata College, and Tom Fisher, Inexpensive Systems, Huntingdon, PA

PIC Projects: Digital Temperature Controller -  Digital temperature controller is an essential instrument in the field of electronics, instrumentation and control automation for measuring and controlling temperatures.  It can be used as much at homes as in...__ Electronics Projects for You

PIC Remote Control -  5 channels are controlled via RF receiver / RF transmitter and PIC12C508 microcontroller.  

PIC Remote Control -  4 / 8 channel RF / IR remote control based on PIC16F628 and PIC16F630 __ Designed by Peter Jakab

PIC12c508 Night Light Saver -  Build a device that turn on and off a night light automatically.  Save Energy, No EMI, No Battery, Built-in Lamp Fixture, and Peak Shaving.   __ Designed by Wichit Sirichote

PIC16c505 IR/Wireless Remote Control -  Control up to 8 devices by this easy constructable remote control.  It can work as a radio or infrared remote control, depending on the components.  Each device output can be configured to be momentary (turned on while you press the button) or latched.  Latched outputs can be toggled on/off by one button per channel, or turned on and off by two buttons per channel. __ Designed by Peter Jakab

PIC16C84/F84 door entry dual code systE - M -  PIC16 Door code entry system __ Designed by Thomas Scherrer OZ2CPU

PIC16F84 LED Chaser -  There are several projects on this page.  Please scroll down to find the LED Chaser.   __ Designed by Jason KE4NYV from Roanoke, Virginia

PIC16f84 Miniature Real Time Controller -  Build a simple real-time controller with PIC16F84 running at low power X-tal 32, 768Hz.  Daily scheduler for 6-channel resided in 64-byte EEPROM can easily be pre-programmed using Nigel PicProg __ Designed by Wichit Sirichote

PIC16F84 RF remote Controller -  With a handful of inexpensive components, a little creativity, and the power of PicBasic, you can build some pretty outstanding robotics creations as Rob Arnold proves with his Ruf-Bot project.   __ Designed by Rob Arnold

PIC16F873 Light Controller -  On these pages, I will introduce the Ultrasonic Range Meter with PIC16F873.  As for the range meter which doesn't use PIC, refer to "Ultrasonic Range Meter".  I created the PCB pattern for this circuit using EAGLE CAD.  With this circuit, the following features of PIC16F873 are used.   __ Designed by Seiichi Inoue

PID Temperature Controller -  What's a PID controller? PID stands for "proportional integral differential" and relates to a process which seeks to continuously correct the error between a measured variable and a desired setting by calculating an appropriate correction process.  In practice, it can largely avoid the large overshoots and undershoots that occur in simple temerature control systems.__ SiliconChip

Pinewood Derby Finish Line Detector -  The following is an electronic schematic and parts list for the items needed to construct an infrared detector for the finish line of a Pinewood Derby racetrack utilizing an external power supply and the parallel port of an IBM compatible computer of at least 486/33Mhz running DOS 3.1 or better.  Also included is a narration concerning the construction of the detector as well as the BASIC code required to operate the detector.   __ Designed by Pack 471

PIR to IR remote control -  After the third attack on my car in 6 weeks, loosing 35 litres of fuel and generally having my day stuffed upI got really pissed off and embarked on the EKM-1 surveillance camera system.  Next time I want to get the act on video.  My first thought was to keep it simple and use a PIR (passive Infra-red) motion detector to set off an alarm in my bedroomthen I would manually start my VCR and record video from a low-light camera __ Designed by Eddie Matejowsky

Plane Motor Controller with High-Rate ESC, BEC & Brake -  This electronic speed control (ESC) for brushed motors combines the features of two of my earlier designs.  One was a high-rate 30A ESC with a brake, and the other a high-rate 12A ESC with a BEC (receiver battery eliminator circuit).   __ Designed by Stefan Vorketter

PLL implements FPGA-based SDRAM controller -  EDN-Design Ideas March 26, 1998    [ NOTE : File has multiple design, scroll for this one.]  As FPGA capabilities increase and time to market decreases, FPGAs gain more acceptance for implementing both data and control paths. Thus, they find wide use as controllers and datapath glue logic for fast-page DRAMs. __ Circuit Design by Eddy Debaere, Barco Graphics, Ghent, Belgium

PLL-based converter controls light source -  EDN-Design Ideas July 2, 1998        [ NOTE : File has multiple design, scroll for this one.]  Using the circuit in Figure 1, you can digitally control the light intensity of a lamp.  The control loop is based on a PLL, in which the VCO comprises a light-to-frequency converter (TSL220) coupled to a light source that derives its drive from a switching regulator (L4970A).  The output of the phase/frequency comparator (4046) serves as the control voltage for the switching regulator.  The control voltage is proportional to the frequency error between the reference frequency (fREF) and the signal frequency (fIN) coming from the light-to-frequency converter. __ Circuit Design by Masso Gottardi, ITC-IRST, Trento, Italy

Pocket LED Light -  An LED pocket light operates with only one cell of battery.   __ Designed by The Electronic Lives Manufacturing-presented Chan

Pocket Lightning Detector -  Schematic + Info + pictures __ Designed by Lennie Zink

Pocket stroboscope -  This circuit is a mini storoscope which you can make so small that it can fit into your pocket.  The circuit is not very powerful, but is works out of two small 1.5V batteries for an hour constantly and maximum flash rate.  The flash rate is variable from zero to about 10 Hz.  Quite nice small device to have with you in parties to gain attention __ Designed by Tomi Engdahl

Pocket white-LED torch is power efficient -  04/30/13  EDN-Design Ideas This single white-LED torch can be housed in an empty glue-stick tube and has a long rechargeable-battery life.   __ Circuit Design by Raju Baddi

Police Lights -  These two circuits flash the left LEDs 3 times then the right LEDs 3 times, then repeats.  The only difference is the choice of chips.  __ 555-Timer

Porch Light Slave Switch -  This circuit turns on the porch light when a passive IR security light is activated.   __ Designed by Andrew R. Morris

Porch Light Switch -  This circuit will activate a relay when light falls to a preset level.  Light level can be adjusted with VR1 and the relay contacts may be used to operate an external light or buzzer.   __ Designed by Andy Collison

Portable Lamp Flasher -  Here is a portable, high-power incandescent electric lamp flasher.  It is basically a dual flasher (alternating blinker) that can handle two separate 230V AC loads (bulbs L1 and L2).  The circuit is...__ Electronics Projects for You

Portable Signal Wand -  Flashing lights have varied applications.  For example, travelers can use these as warning beacons on highways to catch the attention of the public in case of an emergency.  Described here is...__ Electronics Projects for You

Position Detectors provide Motor-control logic -  05/24/01 EDN-Design Ideas In the circuit of Figure 1 , assume that a brush-type dc motor must drive a load back and forth between two endpoints on a lead screw.  Optical sensors determine end of travel, and an SPDT switch selects to which end to send the load.  The sensors themselves supply all the necessary directional logic, and a TRIAC powers the motor with the necessary polarity of half-wave pulses from the 13.   PDF have several circuits, scroll for this one __ Circuit Design by Steve Pomeroy and Russell Hedges, Elgar Corp, San Diego, CA

Pot Controlled Variable LED Intensity Circuit -  The circuit below uses power from four rechargeable AA NiMH
cells to drive 3 white LEDs.  A potentiometer varies the duty cycle of a pulse width modulator circuit to vary the intensity of the LEDs from 0% to 100%.  The beauty of the circuit is that when the. . . Circuit by Dave Johnson P.E.-September, 2009

Power 220V Flashing LED -  AC mains operated single LED flasher circuit, built using the popular CMOS timer chip TLC555 is shown below.  The whole circuit is powered directly by the grid supply of 230VAC through a capacitive potential divider and associated components.  This minuscule Power LED Flashing circuit can be easily fit inside a very small __ Designed by T.K. Hareendran

Power Amp-Single Polarity Power Supply-Using Model 423  -  No description, just schematicOpAmps Lab Inc is the manufactor ofAmplifiers (Video / Audio / Distribution / Microphone / Equalization / Line / VCA / Power), Switchers (Routing / Assign / Matrix), Mult (Press) (Network-Feed) Boxes, Audio Transformers, Oscillators, Power-Supplies, Custom Sub-Systems.  __ Application OpAmps Lab Inc.

Power Backup using Supercapacitors & Optional Keep-Alive Cell -  The LTC4415 contains two monolithic PowerPath ideal diodes, each capable of supplying up to 4A with typical forward conduction resistance of 50mΩ.  The diode voltage drops are regulated to 15mV during forward conduction at low currents, extending the power supply operating range and ensuring no oscillations during supply switchover.  __ Linear Technology/Analog Devices App Note, Dec 5th 2011

Power flasher -  There is no need to resort to complex circuitry if what you are looking for is a simple power flasher.  The light will flash at around 1Hz with a 100W bulb at a duty cycle of 50%.  The max.  load that can be driven with this circuit is 200W and if you wish to have a different frequency

Power Flasher (PAGE 113) -  Suitable for alerting purposes.  Drives 12V Car bulbs __ Contact: Flavio Dellepiane, fladello @ tin.it

Power Gain Stages for Monolithic Amplifiers -  Linear Technology AN18 __ Designed by Jim WilliamsMar 1st, 1986

Power Line Alarm -  This circuit will activate a beeper alarm whenever the AC line voltage is less than 100vac.. . . Circuit by David A. Johnson P.E.-July, 2006

Power Off Time Delay Relay -  The two circuits below illustrate opening a relay contact a short time after the ignition or ligh switch is turned off.  The capacitor is charged and the relay is closed when the voltage at the diode anode rises to +12 volts.  The circuit on the left is a common collector or emitter follower and has the advantage of one less part since a resistor is not needed in series with the transistor base.  However the voltage across the relay coil will be two diode drops less than the supply voltage, or about 11 volts for a 12.5 volt input. __ Designed by Bill Bowden

Power Output Stage Automatic Bias System Control IC LT1166 -  DN126 Design Notes__ Linear Technology/Analog Devices

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