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Computer Interface Circuits

Computer Interface: 
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Last Updated: December 20, 2017 05:05 AM

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

Serial Receiver-32 Bit This is the schematic for an FM transmitter   (57.6 K Baud TTL & CMOS ) with 3 to 3.5 W output power that can be used between 90 and 110 MHz.  Although the stability isn't so bad, a PLL can be used on this circuit.   __ Designed by Bill Bowden

Serial to parallel converter-connect a large number of digital outputs to a PC parallel port In this page you will find the description of a serial to parallel converter designed to connect a large number of digital output to a PC parallel port.  This isn't an "autonomous" circuit but should be used with other circuit, as a Micro-step driver or Unipolar step driver

Serial-Controlled Postage Stamp Computer Governs Process 10/13/94 EDN-Design Ideas The tiny, $39 BASIC Stamp computer makes a nifty low-cost, easily programmed, RS-232C process controller (Parallax Inc, (916) 721-8217).  In the circuit in Fig 1, the BASIC Stamp computer accepts commands via its RS-232C port. __ Circuit Design by Steven C Hageman, Calex Manufacturing Co Inc, Concord, CA

Serial-Interface infrared remote control This is a simple, cheap device that can be connected to any serial port to control most components that have infrared remote controls.  I designed and built it (on a solderless breadboard) in 1991.  In 1992 I wrote a lengthy description of it for an electronics class.  In 1994 I finally designed a PC board for it, using a free, X-based PC board design program called pcb, and in 1995 I etched several of the boards and made the final product __ Designed by John DuBois

Series Resistors, Body Capacitance Scan 16 Buttons with Two MCU Pins In an application using a pin-limited microcontroller (MCU) , I needed to scan an array of 16 buttons.  The technique I used involved a series string of resistors of identical value connected between two bidirectional pins of the __ Designed by Dave Vanden Bout

Shared-Memory Interface Eliminates Arbitration 08/01/96 EDN-Design Ideas The design of a shared-memory interface for the ISA bus commonly requires a relatively complex arbiter, which grants access to an onboard device or to the ISA bus.  If an on-board device requires only infrequent accesses, the circuit in Figure 1 can eliminate the need for the arbiter.  Local access occurs during the execution of an ISA refresh cycle, thereby eliminating any risk of contention.  The RFRSH line signals the beginning of the refresh cycle; as long as this signal is active, the local device has full control of the memory. __ Circuit Design by Piotr Mazur, Wikom, Warsaw, Poland

SHARP palm-top/hand-held to RS232 serial converter This document details how to build your own SHARP palm-top/hand-held to RS232 serial converter.  In summary, this device allows the SHARP range of hand-held computers and pocket organisers to be interfaced to (almost) any computer which has an RS232 serial port i.  e.  IBM-PCs (or compatibles) , Amigas, SUNs, other UNIX machines, etc __ Designed by Andrew Woods

Short Protected Power Supply From PC 12V Supply This circuit provides a short circuit protected power supply from PC 12V supply voltage.  This is particularly handy when working with PC interfacing projects.   __ Designed by M Asim Khan asimkhan @ sat.net.pk

Signal-Powered Switch Connects Devices 05/10/12  EDN-Design Ideas Use a switch to selectively connect a terminal, personal computer, or any other originating device to one of four receivers.   __ Circuit Design by James Dean, National Research Council, Ottawa, ON, Canada

Silent Fanless Computer Power Supply There are a few different ways of doing this but basically you have to make the heatsinks NOT live and you have to provide better cooling for the transistors.  The heatsinks used in PSUs are generally soldered to the PCB via little metal tabs and current usually flows through them, ie they are live with voltage and act as part of the circuit.  What you have to do is cut the tabs which takes the heatsinks out of the circuit and them use wire to replace them in part of the circuit.  

Simple Circuit AVR Programmers These are four different AVR programmers that can be controlled via standard ports of a PC.   __ Designed by The Electronic Lives Manufacturing-presented Chan

Simple Circuit Current Limiter Protects Open-Collector Open-collector outputs are useful for transmitting buffered digital/pulse signals to the external world when high drive is needed.  In harsh operating environments like automotive systems, however, these signals need to be protected __ Designed by Vishwas Vaidya

Simple Circuit Device for Connecting Serial Instrument with RS485 or RS232 to the Internet The device that converts RS485 and RS232 to the ethernet LAN has been developed.  The device was built with the Lantronix XPort embedded ethernet server and the industrial standard differential RS485 transceiver, 75176 and the single-end RS232 driver, MAX232.  The XPort module provides 10/100 ethernet port and the +3V logic UART.  The 75176 and MAX232 are +5V TTL logic __ Designed by Wichit Sirichote

Simple Circuit Efficient All-In-One USB Power Management IC Solution DN1008 Design Notes__ Linear Technology/Analog Devices

Simple Circuit fixture Determines leakage of capacitors & semiconductor switches 06/07/07 EDN-Design Ideas The low input-bias current of a voltage-follower op amp allows this simple fixture to measure the leakage current of capacitors and reverse-biased active devices __ Circuit Design by Marián Štofka, Slovak University of Technology, Bratislava, Slovakia

Simple Circuit FSK Modulator 10/11/01 EDN-Design Ideas The need for a compact telemetry system poses a challenge for designing a small, light, low-component-count system.  Interfacing serial data from the microprocessor is also difficult because most low-cost RF transmitters do not accept dc levels at the input.  Commercial FSK(frequency-shift-keying] modulators are bulky and need many passive components __ Circuit Design by Shyam Tiwari, Sensors Technology Ltd, Gwalior, India

Simple Circuit FSK Modulator Enables Data Transmission Over Low-Speed Link 06/11/09 EDN-Design Ideas Send digital data over a low-speed link.  FSK (frequency-shift keying) is a type of signal modulation for transmitting digital data over an analog communication link.  An FSK modulator comprises a digitally controlled sine-wave generator whose frequency shifts between two predetermined frequencies in response to the two logic levels of the digital data.  The circuit in Figure 1 generates a sine wave by continuously sampling a single sine cycle.  The output of IC2A is proportional to the currents through R1, R2, and R3.  These resistors connect together at one end to the inverting input of IC2A, which is biased at VCC/2.   __ Circuit Design by Israel Schleicher, Prescott Valley AZ

Simple Circuit Ft245 USB Oscilloscope for the PC If you are thinking about adding a USB interface between your project and a PC, read on.  Implementing USB is now easier than you think.  Eddy Insam will show you how.  The USB (Universal Serial Bus) provides a new way of interfacing low and medium speed peripherals to personal computers.  That old workhorse, the RS232 connector, is fast becoming obsolete, even becoming absent in newly purchased PCs.  

Simple Circuit MIDI interface Tester Sometimes when experimenting with different soundcards and MIDI interfaces it is useful to see if there is some data going in MIDI interface.  This can be easily tested with this adapter, which converts the midi signals to visible light pulses.  Just the circuit and plug it to the MIDI output of your computer.  When computer sends any midi data out, you see the LED flashing.  I found this tester very useful in testing homebuilt soundcard MIDI interface. __ Designed by Tomi Engdahl

Simple Circuit Module Gives Voice to PC 05/26/94 EDN-Design Ideas The circuit in Fig 1 uses the ISD1020A voice-record/playback chip(Information Storage Devices, San Jose, CA,(800] 825-4473] to allow an IBM PC to speak and hear.  The analog part of the circuitry comes from the company's application notes __ Circuit Design by Jerzy R Chrzaszcz, Institute of Computer Science, Warsaw University of Technology, Warsaw, Poland

Simple Circuit Monovibrator uses three PLD pin 09/28/95 EDN-Design Ideas If your design requires a precise monovibrator, you don't want to use the circuit in Fig 1.  However, if sharp timing isn't crucial and you can afford just three spare PLD pins, this circuit is an alternative to using yet another 555.  The circuit comprises asynchronous logic, an open-collector-like driver that controls the discharge of an external capacitor __ Circuit Design by Jerzy Chrzaszcz, Warsaw University of Technology, Warsaw, Poland

Simple Circuit Mouse Smart card programmer This "SimpleMouse" Smartcardprogrammer can be used to read and write most of all asyncSmartcards (Processorcards) , including the new "Hornet and +1" DPSC΄s in update and reprogramming mode  __ Designed by source:Keule

Simple Circuit Parallel (Printer) Port Interface This is the basic interface I used as part of my Computerized Room project.  This is the parallel interface only.  The 8 bit input card can be found, along with the rest of the project, at Computerize Your Room/House.  This interface, as well as the other two interfaces, came from the book "The Robot Builders Bonanza", by Gordan McComb.  This interface is also useful for controlling small robots, etc.   __ Designed by Aaron Cake

Simple Circuit PC Data Acquisition If you need to add simple data acquisition capabilities to your PC, then look no further than the Analog Interface Unit.  The Analog Interface Unit (AIU) is a simple circuit that connects to a PC parallel port, and allows you to sample and output 8-bit analog signals under software control.  Here are some of the features : 8-bit ADC and DAC, 

Simple Circuit PC Thermometer In this article building of a simple thermometer for PC will be described.  The unit is extremely simple and cheap to build.  You will only need one NTC resistor, one diode and capacitor and serial port connector.   __ Contact: IQ Technologies

Simple Circuit Printer Emulator Adapter This circuit is a simple adapter for PC parallel port to think that there is a printer connected to computer.  This adapter is useful for testing printing speed with different software and as a part of your own designs. 
You can use this circuit to connect your simple circuits to the parallel port __ Designed by Tomi Engdahl

Simple Circuit QRSS callsign keyer based on an Atmega AVR programmed in C Microcontroller based electronic circuit __ Designed by Hans Summers

Simple Circuit Radio Clock for PC's The heart of the device is a EM2S receiver module and matching antenna.  The two are matched, so a mixing a 60kHz receiver board suitable for the MSF and WWVB signals with a 77.5kHz antenna and vice versa will not work.  It should be noted that the receiver boards know nothing about the format of time signal itself so a 60kHz pair suitable for receiving the MSF signal will also receive the WWVB signal __ Designed by Jonathan A. Buzzard

Simple Circuit RS232 Level Converter based on a MAX232 including Eagle PCB & schematic files This converter comes as an aid to STK500 board.  It uses the famous MAX232 for the signal level translation.  It requires a 1 to 1 rs232 cable for the connection with the PC.  __ AVR Projects Dim

Simple Circuit RS-232 Serial Port Buffer This is a simple serial port buffer circuit I designed for a friend to speed up his SLIP connection in campus computer network "TRINET" of Helsinki University of Technology. The problem in the network was that the RS232 commections from rooms to terminal server were long and made of bad quality wiring. __ Designed by Tomi Engdahl

Simple Circuit RS232C Level Converter using Transistors Cheap and easy circuit for converting TTL logic to RS232C level using small signal transistors.   __ Designed by Wichit Sirichote

Simple Circuit RS422 Converter for Minilogger Build a simple RS422 converter for the Minilogger.   __ Designed by Wichit Sirichote

Simple Circuit stepper Motor driver for PC parallel port A stepper motor has four coils.  The direction of rotation (clockwise or anti-clockwise) depends on the order in which the currents supplied to the coils are switched on.  If you use the motors type 55SI-25 DAYA, having a connector as shown below,  __ Designed by © David Hoult

Simple Circuit Technique Makes 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 2×2 in.  to more than 7×4 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

Simple Circuit Wireless Radio Data Link This is a description of a very simple unit designed and constructed for use as a wireless data connection between two nearby computers.  The error rate is excellent over short runs, and the transmission speed means that a useful PPP link can be established between the machines.  Which are, of course, running Linux

Simples sort out the highest voltage 11/09/06  EDN-Design Ideas Greatest-of-three voltage detector drives indicators and external display __ Circuit Design by Ezio Rizzo, Nova SNC, Genoa, Italy, and Vincenzo Pronzato, Felmi SRL, Genoa, Italy

Simplified Analog Input Schematic This circuit is a track and hold.  The idea is that the input waveform may reach a peak at any instant as the drummer strikes the pad.  When that occurs, the capacitor is charged to the peak input voltage.  There is only one A/D converter (ADC0804, see the Main CPU section schematic) , and it takes time for it to convert an input voltage to a 8-bit code.  No matter __ Designed by Paul Stoffregen

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Computer Interface:  #'s         A -  B        C -  E
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