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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:

Phone Intercepter 1 -  PIC Project  This device connects between the phone line, an answering machine, and your phones.  When a phone call comes in, the answering machine picks up the call and informs the caller to enter the access code to ring the phone or to wait for the beep and leave a message.  If the correct code is entered, the answering machine is immediately disconnected while the device generates phone ringing tones on an external speaker.  Picking up any phone causes the device to return to its initial state.   __ Designed by Luhan MonatMesa Arizona

Phone Interceptor 2 -  PIC Project  This unit is an upgrade of the previous phone call interceptor.  Instead of using an answering machine to provide the outgoing message and recording functions, it uses the ISD4004  (from Windbond Electronics) .  The ISD4004 records up to 8 minutes of audio.  I use the first several seconds for outgoing message prompts.  The remaining time is used to record up to 30 messages, depending on message length.   __ Designed by Luhan MonatMesa Arizona

Phone Line Box -  This is an educational site of PIC Projects in various stages of development along with pictures, source files, object code files, schematics, and board layouts.  You are welcome to use what you like at your own risk.   __ Designed by Luhan MonatMesa Arizona

Phone Messager -  I always keep one totally self powered phone  (the way they all used to work) in case of a power failure.  This device works the same way, taking all of its power directly from the phone line. __ Designed by Luhan MonatMesa Arizona

Phone Screener with Voice -  PIC Project  This unit is an upgrade of the previous phone call interceptor.  Instead of using an answering machine to provide the outgoing message and recording functions, it uses the ISD4004  (from Windbond Electronics) .  The ISD4004 records up to 8 minutes of audio.  I use the first several seconds for outgoing message prompts.  The remaining time is used to record up to 30 messages, depending on message length.   __ Designed by Luhan MonatMesa Arizona

PIC (with source cord) Hexbot robot -  The HEXBOT is constructed from 12  (cheap) model airplane servos.  Each leg moves laterally on one servo and vertically on the other.  Conveniently, this type of servo runs on 5 volts.  These servos need only a specific width pulse to position it.  Once it arrives at its target location, it draws very little power  (about 10 ma) .   __ Designed by Luhan Monat-Mesa Arizona

PIC 5x7 Display -  The PIC board detects 3rd harmonic distortion of AC power line.   __ Designed by Prepared Colin Mitchell

PIC based digital voltmeter (DVM) -  This project will describe how to make a simple digital voltmeter  (DVM) using a PIC16F688 microcontroller.  The range of this DVM is 0-20V, but you can easily increase or decrease the range of input voltage as your requirements after you understand the voltage scaling method described in this project.  The PIC micro reads the input voltage through one of the 8 analog channels and convert it to a 10-bit digital number using the internal ADC __ Contact: Raj Bhatt & Shawon Shahryiar

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 Controlled 32-LED Knightrider -  A PIC processor simplifies the circuit and gives 12 different lighting patterns for the 32 LEDs.  You can use it as a rear window break light as an eye catching display.__ SiliconChip

PIC Controlled DDS VFO 0 to 6 MHz -  This is NOT meant as a detailed building instruction for a DDS VFO.  It is only a few fragments from my experimental work in the shack.  This is "as is" information.  It may contain errors.   However, my own prototype works very well. __ Designed by Johan Bodin, SM6LKM

PIC Debugging routine reads out binary numbers -  12/07/00 EDN-Design Ideas The “burn and learn” method of firmware development excludes an in-circuit emulator and a serial port.   With this method, it is common practice to use spare I/O pins on a mC as a debugging aid.  By strategically placing instructions to set and clear these I/O pins in the codePDF contains multiple circuits, scroll to find this circuit __ Circuit Design by Brad Peeters, Theta Engineering Inc, Costa Mesa, CA

PIC In-Circuit Programming Add-on -  Does your PIC programmer have provision for in-circuit programming? Some such as Microchip's PICSTART Plus don't but you can add this useful function to your programmer by building a simple adaptor!__ SiliconChip

PIC Logic Probe with Pulser -  This project is a combinationLogic Probe and Logic Pulser.  It is capable of testing all sorts of digital and microcomputer projects.  You will find it extremely handy when designing a project as the golden rule is totest everything in steps and stages during the design-and-construction process.  If you are not sure how a Logic Probe or Pulser works __ Designed by Prepared Colin Mitchell

PIC micro LED projects -  Here is a neat PIC Project  that I created using the 16F84 chip and a neat little bi-color LED from Radio Shack.  The LED can be red or green depending on the bias of the diode.  By using two of the PORT B pins, I can control the bias of the LED.  If the LED is on PORT B, Pin 0 and Pin 1, I can set Pin 0 HIGH and Pin 1 LOW, this would make __ Designed by Jason KE4NYV from Roanoke, Virginia

PIC Micro Programmer-MAC, Win98, XP, Vista, DOS, Linux, etc -  This programmer requires only a basic terminal program capable of uploading an ascii PIC HEX file.  It does not matter what operating system or computer  (MAC, Win98, XP, Vista, DOS, Linux, etc.) is used to talk to it.   __ Designed by Luhan MonatMesa Arizona

PIC Micro to Isa Bus Interface -  Schematic Only

PIC Programmer -  As you can see, only a few standard elements are used and the hardware is very simple to build.  So here are only a few words about hardware.  Supply voltage can be either AC or DC.  Voltage Vdd must be between 4.5 and 5.5 V.  For this purpose integrated stabiliser 78L05  (Vdd=5V) is used.  It has current limitation  (protection) 100 mA and with this feature protects inserted PIC from damage in case something is wrong connected.  Programming voltage 13V is provided with 78L08 __ Designed by Bojan Dobaj http://www.picallw.com

PIC Programmer & TestBed -  Easy PIC programming and prototyping.__ SiliconChip

PIC Programmer 2 -  This Programmer is powered by the RS-232 and it works with RS-232 levels at only < ±8.6V.  It programs PIC12C5XX, 12C67X, 24CXX, 16C55X, 16C61, 16C62X, 16C71, 16C71X, 16C8X, 16F8X and ISO-CARD's with ASF.  Other serial programmable chips by adapter.   __ Designed by Jens Dyekjær Madsen

PIC Programmer SCIO Converter -  Programming 18-lead surface-mount SOIC PIC microcontrollers can be a quite difficult because access to the leads is not that easy.  This adaptor PC board accepts 18-pin SOIC PIC microcontrollers and plugs directly into a conventional PIC programmer.__ SiliconChip

PIC Toc-A Simple Circuit Digital Alarm Clock -  What Has less than 20 parts and can wake you in the morning? It's the Pic-Toc alarm clock and it's really easy to build.__ SiliconChip

PIC/AVR Programming Adaptor Board; Pt.1 -  Do you frequently program microcontrollers with a serial programmer? Want to streamline the process so you can quickly do virtually any micro? Well now you can! Our new Programming Adaptor Board, in combination with an In-Circuit Serial Programmer  (ICSP) , allows you to program most 8-bit & 16-bit PIC microcontrollers as well as 8-bit Atmel AVRs.  It has a 40-pin ZIF socket and is configured with just a few DIP switches.__ SiliconChip

PIC/AVR Programming Adaptor Board; Pt.2 -  Last month, we described our new programming adaptor board which works in conjunction with an In-Circuit Serial Programmer  (ICSP) to program most 8-bit & 16-bit PIC and 8-bit Atmel AVR microcontrollers.  Here, we give the details of how to build it and how to use it.__ SiliconChip

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

PIC12F675 PIN PONG -  This project is based on ideas from Rickard's electronic projects page and David B.  Thomas VCR Pong.  However, I have developed the simplicity even further, eliminating most of the external components.  Using microcontrollers with internal 4MHz clock generator there is no need for the xtal.  The 12f675 part also operates on wide voltage range, and the regulator can be removed.  For game controller, I plan on using the old Commodore 64 style paddless.  They include firing buttons, which I plan on using as power switch and game reset.16F675 has a low power sleep mode with 1nA current consumption, so I plan on using that to switch off.  

PIC12F675-Flashing LED -  Simple little circuit for testing PIC12F675 microcontroller.  When you start learning a programming language like C++, Visual Basic or any other language your first step is to write a program that displays "Hello World" on a computer's monitor.  When you start learning how to program PIC microcontrollers an equivalent to that is blinking a LED.  

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


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