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Digital  / Logic Circuits 
Digital Circuits:   #'s - C       D - G       H - M       N - R       S - T       U - Z

Last Updated on: Thursday, November 30, 2017 04:23 PM

Circuits Designed by Dave Johnson, P.E.

Poor Man's TimerOften during testing of certain equipment and components, you would like to keep track of the elapsed time in hours, minutes and seconds.  There are some nice commercial digital timers and counters available for just this sort of application.  However, . . . Hobby Circuit designed by David Johnson P.E.-August, 2008

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

Probe Clip -  PIC Project  Here is how to make a handy test clip.  This clip pierces and clamps on to a wire without much fuss or damage.  Its great for finding what all of those wires do under your dash board.   __ Designed by Luhan MonatMesa Arizona

Processor Controls Watchdog -  01/18/96 EDN-Design Ideas The simple watchdog circuit in Figure 1 allows you to use the same line to provide additional information about the system's operation by closing or opening.    __ Circuit Design by Sergey Velichko, SCP, Boise, ID

Processor Power System Needs No Heat Sink -  DN135 Design Notes__ Linear Technology/Analog Devices

Program turns PC sound card into a function generator -  09/02/99 EDN-Design Ideas You can use a low-cost PC sound card as an analog-function generator by controlling the PC with the program "SoundArb.   " [To obtain SoundArb, download di2409setup.   exe, a 1.06-Mbyte self-extracting installation program.   __ Circuit Design by David Sherman

Programmable charger fills capacitor banks -  10/08/98 EDN-Design Ideas -  (Several Design Ideas, scroll to find this one.)  Designed for the use with a pyrotechnic pulse generator, the charger in Figure 1 uses low-cost components to charge the C1 capacitor bank to a voltage as high as 75V, or to 25V in a few seconds.  A 555 timer, IC1, controls a flyback converter via the Q1 transistor switch.  The converter draws its charging current from a 5V supply.   __ Circuit Design by Dennis Feucht, Innovatia Labs, Townville, PA

Programmable Clock Oscillator -  PIC-Tock is a video clock using a PIC16C61.  In the tradition of Marv Newland's "Bambi Meets Godzilla", there is far too much ROM space spent on credits, which are smooth-scrolled horizontally on the bottom of the screen.   __ Designed by Eric Smith

Programmable Continuity Tester -  Our go/no-go continuity tester giving you the ability to set minimum continuity.__ SiliconChip

Programmable Current Source Powers Charge -  06/22/95  EDN-Design Ideas The circuit in Fig 1 is a digitally programmable current source capable of sourcing currents as high as 2.55A.  The circuit is intended for use in "smart chargers"  (for NiCd or NiMH
batteries containing as many as 10 cells) in applications that require fas __ Circuit Design by Chester Simpson and Fred Hamilton, National Semiconductor, Santa Clara, CA -- 6/22/95

Programmable Digital Code Lock -  A programmable code lock can be used for numerous applications in which access to an article/gadget is to be restricted to a limited number of persons.  Here is yet another circuit of a code lock employing mainly the CMOS ICs and thumbwheel switches

Programmable digital timer switch using a PIC Microcontroller -  Digital timer switches are used to control the operation of electrical devices based on a programmed schedule.  This project describes a programmable digital timer based on a PIC16F628A microcontroller from Microchip that can be

Programmable Ignition System for Car's PT.2 -  There are six versions to build; you choose the one suit your car's ignition pick-up system.  Here's how to build the various modules.__ SiliconChip

Programmable Ignition System for Cars; Pt.1 -  Want to program the ignition timing on your car? Now you can, with this completely new design.  It can be used in older cars which presently do not have electronic ignition or used as an "interceptor" for cars with engine management systems.__ SiliconChip

Programmable Ignition System for Cars; Pt.3 -  As mentioned in Pt.1, the Programmable Ignition System can either be used as a complete ignition system or as an interceptor.__ SiliconChip

Programmable oscillator uses digital potentiometers -  03/07/02 EDN-Design Ideas Digital potentiometers are versatile devices; you can use them in many filtering and waveform-generation applications.  This design idea describes an oscillator in which setting the resistance of two digital potentiometers independently programs the oscillation amplitude and frequency.  Figure 1 shows a typical diode-stabilized Wien-bridge oscillator that generates accurate sine waves fro __ Circuit Design by Alan Li, Analog Devices, San Jose, CA

Programmable PIC-Powered Timer -  This PIC-based timer can be set for any period from one second up to 680 days and even    (theoretically) up to nearly 60 years.__ SiliconChip

Programmable Time Delay Flash Trigger -  Want to try your hand at 'stop motion' photography, where dynamic events such as a match bursting into flame, a drop splashing into a container of liquid or a projectile passing through a light globe, are captured at a crucial moment? Here's a project designed specifically for this kind of work.  It lets you trigger your electronic flash at the precise moment for a great picture.__ SiliconChip

Programming adaptor for 8 & 28 pin AVR Microcontrollers using ISP  -  Okits not pretty, but its practical.  The 20 pin connector at the far right is left over from a diffferent project and is no longer used.  This adaptor lets me program 8 or 20 pin DIP devices using the In-System Programmer    (ISP) described in Atmel's AVR910 application note.  This circuit provides power and clocks for the part to be programmed and power to the ISP circuit.  When programming 8 pin devices, the part is positioned toward pins 1 and 20 of the socket such that the 8 pins of the chip occupy the pins 1, 2, 3, 4, 17, 18, 19, abd 20 of the programming socket.  In the case of an 8 pin part being programmed, the SPST switch that grounds pin 4 must to be closed.  Conversely, when programming a 20 pint part, the switch on pin 4 must be open so the crystal can be used for the clock for the part being programmed.   __ Designed by Dick Cappels

Programming Pulse Generators for Flash Memories -  DN17 Design Notes__ Linear Technology/Analog Devices

Programss Atmel AVR microcontrollers -  30-Mar-00 EDN-Design Ideas Atmel AVR mCs feature an enhanced RISC architecture that purportedly offer the highest MIPS-per-milliwatt capability in the 8-bit mC market.  Figure 1 shows an easy-to-build AVR mC-programming circuit that can program the 40-pin AT90S4414/8515, the 20-pin AT 90S1200/2313,PDF has many circuits, scroll to this one __ Circuit Design by Guo-Yin Xu, XuMicro, Houston, TX

Propeller Message Display with Temperature Indicator -  Here we describe a microcontroller-based propeller display that displays any message sent to it via hyper-terminal of a personal computer.  Moreover, a temperature sensing IC (TMP125) is mounted onto the propeller...__ Electronics Projects for You

Propellor clock PIC16F84 -  A motor spins the "propeller", and a small microprocessor keeps track of time and changes the pattern on seven LEDs with exact timing to simulate a 7 by 30 array of LEDs.  It is an illusion, but it works nicely.   __ Designed by Bob Blick

Protoboards: the Easy Way Into Electronics -  Use a protoboard to build a light chaser.__ SiliconChip

Protoboards: the Easy Way Into Electronics, Pt.4 -  Fun with comparators: this month we play with the LM393 "bog-standard" dual comparator.__ SiliconChip

Protoboards:The Easy Into Electronics -  More fun with comparators: making a window comparator.__ SiliconChip

Protoboards:The easy way into Electronics Pt.3 -  More circuit boards based on the 555 timer and how to use the 555 as a audio amplifier.__ SiliconChip

Prototype Board-Atmel 89C2051 -  This single sided proto board provides an economical solution for developing and testing the projects around Atmel 20 pin series u-controllers  (89Cx051 & AVR)  __ Designed by M Asim Khan    asimkhan @ sat.net.pk

Provide Watchdog for Microcontrollers -  12/26/02  EDN-Design Ideas The watchdog circuit in Figure 1 uses a single NAND Schmitt-trigger IC.  The circuit iscost-effective than dedicated, commercially available watchdog ICs.  The circuit generates an active-high reset signal upon power-up and remains i __ Circuit Design by VM Holla, Bangalore, India

Push Button Switch Debouncer -  This circuit will remove the transient spikes and contact bounces from a non-latching push button switch.   __ Designed by Andy Collison

Pushbutton or logic controls nonvolatile DACs -  11/19/98 EDN-Design Ideas NOTE :  File contain several designs.  Scroll to find this one.  For manual control of analog signals, it's hard to beat the venerable precision multiturn potentiometer's simplicity, resolution, and power-off nonvolatility.  When digital control of an analog parameter is the design objective, a universe of DACs is available to the designer.  The circuit in Figure 1, however, has manual-pushbutton and CMOS /TTL-compatible digital interfaces to a 10-bit, nonvolatile, two- or four-quadrant multiplying DAC.  The heart of the circuit is the Xicor  (Milpitas, CA) X9511 PushPot series of digitally controlled potentiometers. __ Circuit Design by Stephen Woodward, University of North Carolina, Chapel Hill, NC

Pushbuttons & digital potentiometer control boost converter -  02/17/05 EDN-Design Ideas Digitally controlled potentiometers are useful for generating analog control voltages under the control of a microcontroller.  In some applications, manual pushbutton switches could replace a microcontroller and simplify product design.  Mechanical switches exhibit contact bounce, and, when a user actuates them, they may open and close many times before reaching a stable state __ Circuit Design by Simon Bramble, Maxim Integrated Products Inc, Wokingham, UK

PWM Motor Control -  PIC Project  This device acts as a variable speed control for the heater blower in a car.  It takes its power directly from the existing wiring and connects with just 2 wires.  It will also work for any 12 volt device up to 10 amps.   __ Designed by Luhan MonatMesa Arizona

Quadrature Direct Fourier Transform -  PIC Project  Disclaimer:  I don't know whether this idea is original, I only know that it works.  Normally, doing DFT  (direct fourier transform) means multiplying each data point with the sine and cosine coefficients and then summing the totals for all points.  The resultant sums are then 'vector added' by taking the 'square root of the sum of the squares'.   __ Designed by Luhan MonatMesa Arizona

Quick'n'Easy Digital Slide Scanner -  A simple way to copy slides onto your computer's hard drive.  Do you have a large collection of slides which are deteriorating by the day? Are they growing mouldy or becoming discoloured? Then there is no time to waste.  Get them onto your computer's hard drive before it is too late.  This method is very quick, simple and does not require any electronics.__ SiliconChip

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Digital or Logic Circuits:  #'s - C       D - G       H - M       N - R       S - T       U - Z

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