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Computer Interface Circuits

Computer Interface: 
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Last Updated: December 25, 2017 01:47 PM

Circuits Designed by Dave Johnson, P.E.

Laptop Power Supply Concept Only.  I have a big screen HP laptop computer.  The large brick size AC to DC power supply is rated at 19.2v and 9.5 amps, which is about 180 watts.  Id like to be able to use the thing in my car.  I looked into a 12v car adapter for it but never really found one that I liked. . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2009

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

Jasmin floppy disk controller Schematics So he always stays on course, Jared designed a mechatronic device that simulates perfect steering in an automobile.  The small-scale, single-wheel model determines the speed of wheel rotation from the magnitude of the curve it's traveling.  Gadget Freak / Design News

Java Applet Computes Standard Values 08/17/98 EDN-Design Ideas NOTE :  File has several circuits, scroll to this one.  The Java applet in Listing 1 implements a standard-resistor value calculator in a form that is suitable for use on a Web page or an internal intranet.__ Circuit Design by Vance Campbell, Digital Radio Communications Corp, American Fork, UT

Javabot I have designed it just for fun.  First I want to know how the line sensor work.  I used comparator IC using LM339, two H-bridge sensor using eight transistors, FCS9013, and four transistors, FSC 9012.  For the sensor you can use LED and LDR as the light receiver. __ Designed by Wichit Sirichote

JFET-based DC/DC converter operates from 300-mV supply 5/25/06  EDN-Design Ideas You use a JFETs self-biasing characteristics to build a DC/DC converter that operates from power sources such as solar cells, thermopiles, and single-stage fuel cells, all of which  deliver less than 600 mVYPDF has several circuits, you will need to scroll to find this one __ Circuit Design by Jim Williams, Linear Technology Corp, Milpitas, CA

Joystick Interfaces This is a very simple circuit to interface a current loop sensor to an input which is designed for a voltage, such as that from a standard potentiometer.  This page is technical so that interested persons can build the circuit themselves, but 4QD can also supply the interface on a 'postage stamp' sized (22mm x 27mm) board as shown in the first diagram.  It is a relatively trivial circuit! __ Designed by Richard Torrens

Joystick Interfaces This is a page of analogue interfaces for joysticks.  Although these interfaces have been developed for use with 4QD's controllers they will have plenty of other uses.  Also because of the development history, we have printed circuit boards available (either fully populated and tested) or bare boards) for these interfaces. __ Designed by Richard Torrens

Jupiter card programmer The original hardware and software PonyProg (which can be used for Jupiter Card programmer II) is presented in Lanconelli Open Systems.  A SmartMouse oscillator is used insted of original circuit to prevent problems, which are announced by error message "Device missing or unknown device (-24) ".  The serial port of PC is used for connection.  This programmer is compatible with so-called "Harpune" programmer

KD2BD Pacsat Modem The KD2BD Pacsat Modem is a low cost, high performance 1200 bps BPSK modem designed to interface between a packet radio terminal node controller (TNC) and an amateur satellite ground station, and allows full-duplex access to the 1200 baud "Pacsat" constellation of amateur satellites. __ Designed by John A. Magliacane, KD2BD

Kenwood TM451 TCXO Upgrade Being used in a mountain-top repeater, our TM451 transceivers suffered severe frequency shifts as the temperature varied.  They are exposed to temperatures as low as -15C in winter and as high as 45C in summer, and the original crystal oscillator is too sensitive to this variations.  We measured the repeater to be as high as 2.5Khz up or down in frequency depending on ambient temperature, and we looked for a solution.   __ Designed by Roberto Barrios EB4EQA

Key reading saves I/O pins 6-Mar-03 EDN-Design Ideas Some microcontroller applications usually use too many I/O pins to read keys or onboard switches; in many cases, few pins remain available for other uses.  Some alternative ways to read keys yieldfree pins.  First, consider some ways to effect key reading.  Table 1 presents a comparison of four methods with references to circuit configurations(figures 1, 2, 3, and 4] __ Circuit Design by Gustavo Santaolalla, Digital Precision Systems, Buenos Aires, Argentina

Keyboard Wedgie A "keyboard wedge" is a device for connecting between a keyboard and computer for automatically entering information, as though it were typed, avoiding the need for a special program to be running on the computer.  The Keyboard Wedgie is a lightweight version for entering binary data into a spreadsheet or other program.  It uses a small PicAXE processor to measure a voltage with 10 bits resolution and enter that value, in binary, into a desktop computer, typically into a spreadsheet program.  It replaces either an old serial keyboard or a USB keyboard and will work with another keyboard attached, in most cases.  This abbreviated device can only punch three keys, the "0, " "1, " and "enter" keys, just enough to enter a binary value into sequential cells in a spreadsheet or lines in a text editor.  Since the Keyboard Wedgie simulates key presses, it will work with just about any keyboard system without any knowledge of the signaling protocols.  It, after all, just presses buttons.   __ Contact: Charles Wenzel of Wenzel Associates, Inc.

KORG Triton CF Upgrade Tired of floppy and Jazz disks, I looked for a better storage solution to install in the Triton.  I tried a Floppy-to-USB emulator and it worked well but the 1.44MB limit was still there.  Although a bit more complex, using a SCSI>IDE adaptor and a IDE CF reader looked very well on paper.  So I got a I-O Data R-IDSC-E/R adapter with firmware 1.30.9 and a IDE CF reader in a floppy drive form factor __ Designed by Roberto Barrios EB4EQA

Laptop Audio Amplifier This circuit uses a power amplifier IC LA 4440 and two 6 watt speakers to amplify the audio output of a laptop.  __ Electronics Projects for You

Laptop Computer Serial Port Power Booster If you are looking at this page, you probably feel like I did when I tried to run a self-powered PIC programmer with my notebook computer.  Yes, the serial port was the ultra-low-power type and wouldn`t provide enough current to power the programmer.  The problem was clear and so was the solution.  I could have modified the programmer to get the power from somewhere else, but in the future I悲 crash with the same wall. __ Designed by EB4EQA

Laptop Power Supply Concept Only.  I have a big screen HP laptop computer.  The large brick size AC to DC power supply is rated at 19.2v and 9.5 amps, which is about 180 watts.  Id like to be able to use the thing in my car.  I looked into a 12v car adapter for it but never really found one that I liked. . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2009

Laptop Protector Protect your valuable laptop against theft using this miniature alarm generator.  Fixed inside the laptop case, it will sound a loud alarm when someone tries to take the laptop.  This highly...__ Electronics Projects for You

Laser Printer Prototypes PC-Board Artwork 05/12/94 EDN-Design Ideas A nifty method for generating artwork for prototype pc boards uses an ornamental foil originally made to simply dress-up printouts.  To use LaserColor foil (Minds In Motion, PO Box 679, Lindhurst, NJ 07071), first draw the artwork, positive or negative, using any drawing program.  Whatever is black on the printout becomes opaque on the finished artwork.    __ Circuit Design   Raj Shah and Dan Meeks, Q-bit Corp, Palm Bay, FL

Lazy ISP Adaptor for Socketed AVR ISP Controllers The Lazy Adapter is composed of a 20 pin DIP socket, a 20 pin DIP header, and 6 pin ISP header, and a small phenolic circuit board to hold them all together.  The green fiberglass PCB is a Dontronics DT104 SIMSTIC (This plug is in return for a favor.)  __ Designed by Dick Cappels

LCD 2 USB LCD2USB is a open source/open hardware project.  The goal of LCD2USB is to connect HD44780 based text LCD displays to various PCs via USB.  LCD2USB was meant to be cheap and to be made of easily available parts.  It is therefore based on the Atmel AVR Mega8 CPU and does not require any difficult to obtain parts like separate USB controllers and the like.   __ Designed by Till Harbaum <Till @ Harbaum.org>

LCD Interfacing with VB How to interface the LCD with Visual Basic.   __ Designed by Wichit Sirichote

LCD Thermometer 2nd version of Thermistor Thermometer __ Designed by Wichit Sirichote

LCD2LPT with LIRC The "LCD2LPT with Lirc" circuit is the compilation of two circuits found on the net on a single board.  The first is LCD to LPT interface and the second an IR remote control interface using http://www.  lirc.  org program.   __ Contact: IQ Technologies

LED & Piezo On One Line using a PIC16c508 Scroll to find this circiutOne of the simplest combinations is a LED and Piezo on a single drive-line as shown in fig: 1.  These can be combined because the requirements of a LED are different to a piezo.  A LED requires a constant HIGH for it to illuminate while a piezo requires a HIGH-LOW-HIGH waveform at approx 3kHz to produce a tone.   __ Designed by Prepared Colin Mitchell

LED & Push Button On One Line using a PIC16c508 Scroll to find this circuit # 2In this book, we show how to connect two and up to five or more push buttons on a single input line and generally you will not have any problems adding buttons to a project.  But if you want to add a secret reset button (or a "cheat" button, for example) , it can be added across an existing LED as shown in fig: 3.   __ Contact: Colin Mitchell

LED Light A simply and easy-to-make circuit, useful when working with the computer at night.  (6/08/2006)  __ Designed by Jose Pino

LED Load The board supports driving two separate tri-color LEDs.  More can be setup inline if desired.  Currently the software only uses the second LED and its color represents the CPU load of the system in real-time.  Blue for idle and gradients light blue, green, yellow, orange, and finally red indicating heavy CPU utilization.  If the system fails to respond, the LED begins flashing RED to indicate a lack of communication from the software.  This lets you easily identify a crashed machine in a rack for example.  

Lego Mindstorms RCX IRPD Interface Several Projects, scroll down.  Long have I wanted to get a better proximity detector for my Mindstorms robots, now I have one.  When I found the Lite-On IR modules and the new Sharp IS1U60's it looked like a match made in heaven.  However, these newer, smaller units are more sensitive and far more picky.  I had to re-write my code to get them to work well and try to cut down on their sensitivity.  The PIC program I used for this project has the exact same code as that in my IRPD project above, it just requires more "hits" to go over the sense threshhold because this IR demodulator is so much more sensitive____ Designed by Dennis Clark

Line Driver Economically Synthesizes Impedance 01/06/94 EDN-Design Ideas The line-driver circuit in Fig 1 uses a second op amp to synthesize the output impedance.  The conventional line-driver circuit employs a single op amp having a resistor whose resistance is equal to the desired impedance in series with the op amp's __ Circuit Design by Victor Koren, Orckit Communication Ltd, Ramat-Gan, Israel

Line ReversalUsing a PIC16c508 Scroll to find this circuit #4- If a device is connected between two output lines as shown in fig: 5, a program can be written so that the device sees a voltage reversal.  When one output is HIGH the other is LOW and this is then reversed.   __ Contact: Colin Mitchell

Link Neatly Measures Temperature 10/26/00 EDN-Design Ideas Figure 1 shows a convenient and neat way to measure temperature using the USB of a PC.  An ADM1023 IC senses the temperature, and an Anchor Chips EZ-USB AN2131SCC provIdeas control.  The ADM1023 is a low-cost device with an accuracy of 1C and a resolution of 0.125C.  The IC is a two-channel device that can measure its own local temperature and the temperature of a remote location __ Circuit Design by Mary Burke, Analog Devices, Limerick, Ireland

Linux Infrared Remote Control LIRC This manual will guide you through the installation and configuration of LIRC.  Setting up LIRC currently is not an easy task.  So please take some time to read this documentation carefully.  If you don't understand a part of this manual or if you think there is something important missing you should complain __ Designed by Christoph Bartelmus

Live Telecasting On Your Web Presented here is an Internet-based project for telecasting live video from your computer to your webpage.  The video can be viewed on the computers of your family members, relatives or friends...__ Electronics Projects for You

Look-up table facilitates bit flipping 11/23/00 EDN-Design Ideas In certain instances in embedded software, it becomes necessary to flip the order of bits in a byte, so that B7:B0 becomes B0:B7.  For example, this feature could be useful with a synchronous serial port that does not allow programmed selection of bit order(MSB first or LSB first]for its shift register.  If a device to which the processor sendsPDF has several circuits, scroll down to find this one __ Circuit Design by Brad Bierschenk, High End Systems, Austin, TX

Low Cost PC-Board Shields 02/19/04 EDN-Design Ideas Many pc-board assemblies require shields to reduce susceptibility to interference from electromagnetic fields.  A classic example is a radio receiver, in which the front end usually needs high isolation from the tuning synthesizer.  Historically, shields for low-volume or low-cost applications involve trade-offs.  You can't justify the cost of a custom-cast shield, and shields machined from aluminum burn through money as fast as the end mills go dull.  You can make a simple shield for just a few dollars by using commonly available die-cast aluminum "project boxes, " such as those from Hammond Manufacturing (www.  hammondmfg.  com).  These boxes come in sizes from 22 in.  to more than 74 in.  You turn the project box into a shield by sandwiching the pc board between the top and the bottom of the box, thus completely enclosing the sensitive circuitry.   __ Circuit Design by Steve Hageman, Windsor, CA

Low-Cost PC-to-I2C Interface for Debugging Tracking down problems in circuits which are programmed via an I2C bus can be tricky and time-consuming, unless you take advantage of a debugging program running on a PC.  Here's a low-cost, easy-to-build printer port to I2C interface designed to work with the Philips/NXP debugging program URD312.exe.__ SiliconChip

Low-cost programs EEPROMs 01/04/01 EDN-Design Ideas When you migrate to 3.3 V system supplies, you must usually replace your old, reliable EEPROM programmer with a new, overly flexible and expensive universal programmer.  We could not find a 3.3 V programmer for less than $1000.  For  __ Circuit Design by Jarrod Eliason, Ramtron, Colorado Springs, CO

Low-Cost PWM Module for Arduino or Development Kit with Mcu This short article describe simple circuit capable to convert a TTL/CMOS PMW signal to analog signal. The circuit can be used as extension shield for Arduino, with simple MCU or with TTL/CMOS ...__ Electronics Projects for You

Low-Cost RS-232C Multiplexer Serves as Multiport Adapter 03/01/96 EDN-Design Ideas Multiport RS-232C PC add-on boards are intended for intensive multichannel communication.  Therefore, each serial port has its own transmission controller.  If your application doesn't need interrupt-driven service, and polling the devices through RS-232C channels one after another is sufficient, then you can use a single controller with switched input and output signals instead of installing a costly multiport adapter. __ Circuit Design by Jerzy R Chrzaszcz, Institute of Computer Science, Warsaw University of Technology  Warsaw, Poland

Low-Power Car/Bike USB Charger Looking for an efficient USB charger that can operate from a 12V car battery? This unit functions at up to 89% efficiency and can charge USB devices at currents up to 525mA.  Best of all, it won?t flatten the battery if it's left permanently connected, as long as you remember to unplug the USB device.__ SiliconChip

Low-power CMOS oscillator has push-pull output 04/01/04 EDN-Design Ideas Digital oscillators often generate TTL- or CMOS -level outputs, referred to ground.  Generating a symmetric bipolar output with respect to ground presents a challenge.  In this design, four 1.5V flashlight cells create 3V voltage sources, and the midpoint of cells acts as the ground reference(Figure 1).  The oscillator at the input, based on the R1C1 time constant, generates __ Circuit Design by Shyam Sunder Tiwari, Sensors Technology Private Ltd, Gwalior, India

Low-voltage interfaces translate 1.8 to 5V 11/05/98 EDN-Design Ideas (Several circuits here, scroll to find this one) Interfacing two systems that operate at two arbitrary voltages is a challenging problem; there is no guarantee that one side operates at a voltage higher than the other side.  Usually, the interface is an open-collector or open-drain type with just two transistors connecting back to back(Figure 1a].  VX  is the lower of the two operating voltages __ Circuit Design by CC Poon and Edward Chui, Motorola SPS, Hong Kong

LTC1387: 5V RS-232/RS485 Multiprotocol Transceiver DN176 Design Notes__ Linear Technology/Analog Devices

LTC1735 Provides Low Cost Efficient Mobile CPU Power DN199 Design Notes__ Linear Technology/Analog Devices

Luxman A383 DAC Upgrade This old amplifier sounds awesome but I got tired of depending on soundcards or external DAC for the HTPC.  A very annoying issue was the loud POP! sound from the IQ7 speakers every time the HTPC went to or came out from sleep.  Not wanting any more channels than left+right, I did not want to buy a new amp and the hack-upgrade appeared as a reasonable option.  A few weeks of eBay-fishing finally a nice NAD MDC DAC arrived at home.   __ Designed by Roberto Barrios EB4EQA

Luxman System Bus I Interface I decided to study the System Bus I protocol and interface each Hi-Fi component to the main Luxman A383 Amplifier, which had a remote with lots of functions for other devices.  I would build a module with a PIC to decode the commands.   __ Designed by Roberto Barrios EB4EQA

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