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Computer Interface Circuits

Computer Interface: 
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Last Updated: October 24, 2017 02:54 PM

Circuits Designed by Dave Johnson, P.E.

Computer Controlled Power Relay Often there is a need to turn on and off a 120vac device using a low power +5v logic signal from a computer.  The circuit below shows how this could be done.  The circuit uses a power relay with a 120vac coil and 10 amp contacts.  A small solid state relay turns on and off the relay.  The solid state relay provides 5KV isolation from the computer . . . Hobby Circuit designed by David A. Johnson P.E.-July, 2011


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

Computer Audio Booster Here is a simple amplifier for boosting the audio level from low-power sound cards or other audio sources driving small speakers like toys or small transistor radios.  The circuit will deliver about 2 watts __ Contact: Charles Wenzel of Wenzel Associates, Inc.

Computer Controlled Frequency Counter/Logic Probe This circuit is a stable frequency counter accurate to 5 significant digits.  The range is 030MHz with an input sensitivity of greater then 100mV.  The probe connects to the PC serial port.  So by using the crystal oscillator already present on your PC serial card and software calibration, the Probes' external circuitry is kept to a minimum.  Probe 9 can also be used as a logic probe/analyzer using included software (LPROBE92.  EXE) __ Designed by Aaron Cake

Computer controlled infrared remote control transmitter Control all your devices from the PC.  This infrared remote control transmitter can be controlled from a computer.  It speaks many different remote control formats, like the Philips RC-5 standard and can be tailored to other specific types.   __ Designed by Peter Jakab

Computer Controlled Model Train Set I had two objectives in starting this mini project.  One was to help me get a better understanding of using a PC for control and automation.  The other was to make my younger brotherís train set a little less boring.  I never could __ Designed by Submitted Jane L, Northampton

Computer Controlled Power Relay Often there is a need to turn on and off a 120vac device using a low power +5v logic signal from a computer.  The circuit below shows how this could be done.  The circuit uses a power relay with a 120vac coil and 10 amp contacts.  A small solid state relay turns on and off the relay.  The solid state relay provides 5KV isolation from the computer . . . Hobby Circuit designed by David A. Johnson P.E.-July, 2011

Computer Microphone This circuit was submitted by Lazar Pancic from Yugoslavia.  The sound card for a PC generally has a microphone input, speaker output and sometimes line inputs and outputs.  The mic input is designed for dynamic microphones only in impedance range of 200 to 600 ohms.  Lazar has adapted the sound card to use a common electret microphone using this circuit __ Designed by Lazar Pancic

Computer Output Interface A versaile output interface that can control external devices direct from your computer.  Uses freely available software and works with both windows and Linux.   __ Designed by Andy Collison

Computer Powered Receiver Here is a receiver for a laptop or PC that requires no power supply! The receiver is powered by the microphone jack and makes a great dedicated receiver for fixed locations like my outdoor antenna described above.  The 10 megohm at the antenna bleeds off any accumulated charge and the Lumex tube hopefully catches high voltage spikes  __ Contact: Charles Wenzel of Wenzel Associates, Inc.

Computer Speaker Reflex Receiver Here is a version built into a surplus computer speaker using an LM386 audio amplifier IC.  The circuit is built onto a little piece of phenolic perfboard that is secured by wedging the edges of the perfboard into a couple of bifurcated standoffs.  The on-off switch is part of the volume control which is mounted next to the tuning capacitor.  The loopstick antenna is __ Contact: Charles Wenzel of Wenzel Associates, Inc.

Computer to TV Adapter Simple adapter to connect an old computer with CGA video graphics card to any TV.   __ Designed by Jose Pino

Computerize Your Room/Home So you've read about my Computerized Room or have seen those nifty home automation products advertised in the back of electronics magazines? Or perhaps someone you know has done something similar.  At any rate, you have decided to try it yourself.  The first thing I will say, however is that it is not cheap.  You will first need a computer, but since your reading this, I assume that you already have that taken care of.  Second, you will have to buy about 20 IC's and a very expensive ISA experimenters prototyping board.  These boards cost anywhere from $16 to $45, and can be purchased from your local electronics store or from Jameco Electronics (See Where To Get Parts).  They have a fairly wide selection.  Buy the 8 bit version, the 16 bit varsion is not needed for this project. __ Designed by Aaron Cake

Computerized Infrared Remote control your stereo, TV and VCR from Windows, includes schematic and software

Configurable logic gates' Schmitt inputs make versatile Monostables 05/25/06  EDN-Design Ideas You can assemble a pulse-generation circuit from a simple Schmitt-input AND gate plus a resistor-capacitor timing network.  However, if you need a logic function thatís not a standard catalog item, you need a Schmitt-input gate or  __ Circuit Design by Glenn Chenier, Allen, TX

Configurable RS232 to Ttl to I2c Adaptor RS232 signals cover a much longer distance than standard TTL and I2C signals.  Also, RS232 signals have better noise immunity.  RS232 is a well-known standard supported by many popular integrated circuits...__ Electronics Projects for You

Connect a 4◊3 matrix keyboard to a microcontroller using two I/O pins 05/08/13  EDN-Design Ideas To connect a 4◊3 keyboard requires seven digital I/O pins.  This becomes a problem when the project is based on a low-pin-count MCU or when the MCU being used does not have enough free I/O pins.   __ Circuit Design by Aruna Rubasinghe

Connect a Modem to a Basic Stamp 09/16/99 EDN-Design Ideas The 2400-bps modem in Figure 1 makes it easy to connect a Basic Stamp (Parallax Inc, www.parallaxinc.com) to a telephone modem.  Using this circuit, you can call home via your PC and find out if the house is still there.  The Basic Stamp2, BS2-IC, has the necessary programming space, and a 64-kbyte StampMEM memory-storage board enhances site data collection.    __ Circuit Design by Ken Gracey

Connect IEEE-488 Devices to Parallel Port 07/20/95 EDN-Design Ideas The circuit in Fig 1 connects IEEE-488 printers and plotters to a parallel port, using only 10 buffered inverters (74HC or 74LS).  Moreover, the conversion speed is much higher than that of some expensive "intelligent converters," and you don't need to install a special software driver.    __ Circuit Design by Johannes Sturz, Texas Instruments, Freising, Germany

Connect Others to PC Joystick Port PC joystick port can be a very useful interface for simple digital input circuits, because joystick connector has +5V power output, which other standard PC interface connectors don't have.  You need to be a little bit careful with this power output, because it can give quite much current in short circuit situation (up to 20A in some cases).  This current is enough for burning small wires in your circuit or inside your PC (I have burned one flatcable coming form multi-IO card to joytick connector !) __ Designed by Tomi Engdahl

Connect two CD-ROM drives to one soundcard Connect your PIC devices on a shared network, and they can communicate to each other and share information.  You can control them all by any unit on the network.   __ Designed by Tomi Engdahl

Connect Your MicroControllers Into a Network Connect your PIC devices on a shared network, and they can communicate to each other and share information.  You can control them all by any unit on the network.   __ Designed by Peter Jakab

Connecting a Globe using a PIC16c508 Scroll to find this circuit #8 -A globe is a device that requires a very high start-up current.  This is something you may not be aware of.  The start-up or warm-up current for a globe is about 6 times its operating current and although this current is drawn for only a very short period of time, it is one of the reasons why a globe does not work in some circuits.  The high start-up current prevented one of our flip-flop circuits working.  The resistance of the leads from the project to the battery was sufficient to prevent the circuit starting-up.  That's why it is important to remember everything we discuss.   __ Contact: Colin Mitchell

Connecting a Motor using a PIC16c508 Scroll to find this circuit #11In theory you can connect a motor to two drive-lines and get forward and reverse operation.  But unfortunately a motor requires a very high start-up current and the drive lines of a '508A are not capable of delivering this current.  The solution is to use transistor buffers in the bridge arrangement of fig: 16.   __ Contact: Colin Mitchell

Connecting Dumb Terminal Some applications may not need user display and key interface, dump terminal is an alternative way for program setting, displaying user interfacing command.  Debugging, dump terminal connects with serial port, use only 2-i/o pin, P3.0 for Rxd and P3.1 for Txd.  Any computers that has serial port and emulates as a dump terminal can be used for the purpose, the example used PC run terminal emulation program __ Designed by Wichit Sirichote

Connecting LED to PIC Micro I/O pins So, youíve got a great idea for a project using a PICmicro microcontroller and you want to use at least one LED in your project as a power indicator.  Or, maybe, youíve set out to design a bar-graph voltmeter with eight LEDs, __ Sirus MicroSystems

Connecting Minilogger with Easy-Server V0.9 Run Easy-Server V0.9 on PC connected to internet gateway enabling remote access the MiniLOGGER.   __ Designed by Wichit Sirichote

Connecting Nokia 3310 LCD to USB using AVR. Part 1. Schematic What do you do with an old phone, a microcontroller and lots of time? You hook the old phone's LCD screen to the computer USB of course! In this project we're going to communicate with a Nokia 3310 LCD display over USB! How are we going to do that?

Connecting Sega 3D Glasses to a PC Serial Port This documents ties to clear out one method for connecting Sega 3D glasses to PC serial port for cheap PC virtual reality.  This who do no not know what those Sega 3D glasses are, here is a description: __ Designed by Tomi Engdahl

Connector Adds Plug-And-Play Capability 07/04/96EDN-Design Ideas Centronics parallel ports are now widely used to connect everything but printers to PCs.  In most cases, the user must configure the application software for the right port (LPT1: or LPT2:).  However, designing in automatic port recognition is a simple matter.  The connection of an output line to any spare input pin of the DB25 connector is all that is necessary on the hardware side (Figure 1.) __ Circuit Design by Patrick Gueulle, Le Havre Cedex, France

Conntecting a Relay using a PIC16c508 Scroll to find this circuit #9Most relays require more than 25mA for operation and need a 12v supply.  For this a buffer transistor is required.  Fig: 14 shows how a relay is connected to an output of the '508A.  The diode across the relay prevents voltage from the relay getting into any of the supply lines and affecting the operation of the microprocessor.   __ Contact: Colin Mitchell

Control 32 DAC Channels via a Parallel Port EDN-Design Ideas July 8, 1998    This circuit controls 32 voltage-output channels from the parallel port of a PC.    __ Circuit Design by Mark A Shill, Burr-Brown Corp, Tucson, AZ

Control a DC Motor with your PC 08/26/10 EDN-Design Ideas Use the printer port to select three different speeds.    __ Circuit Design by Firas M Ali Al-Raie, Polytechnic Higher Institute of Yefren, Yefren, Libya

Control a processor's power supply in real time 31-Mar-05 EDN-Design Ideas Dynamic control of processor's supply rail minimizes power consumption __ Circuit Design by Yogesh Sharma, Analog Devices, San Jose, CA

Control electrical appliances using PC Here is a circuit for using the printer port of a PC, for control application using software and some interface hardware.  The interface circuit along with the given software can be used with the printer port of any PC for controlling up to eight __ Designed by Radio LocMan

Control stepping Motor via USB interface This is an example that demonstration how to control some devices via USB interface.  The PC software program with delphi.  Feature:, CPU PIC18F4550 with full speed USB interface at 48MHz.  , USB 2.0 compliance, Use on-chip USB driver

Control System Uses Labview & a PCís Parallel Port 26-Jun-08 EDN-Design Ideas A National Instruments LabView diagrammatic program controls the operation of a metered parking lot __ Circuit Design by Carlos Alberto Aguilar SŠndez, Centro de Estudios Superiores del Estado de Sonora, Unidad sede San Luis Rio Colorado, Sonora, Mexico

Controller for Hybrid Power Plant The 89C51 control board for controlling photovoltaic-wind turbine and diesel engine.  Developed by Didik Rostyono from Indonesia.   __ Designed by Wichit Sirichote

Controller for Stepper Motor using 4027 flip-flop & 4070 XOR gate I found this circuit in my files.  I don't know where it came from, but it looks like I photocopied it from somewhere years ago.  I have been told that it came from "The Robot Builder's Bonanza", by Gordan McComb.  Anyway, I thought that it should be fairly useful, so I decided to post it here.  The circuit is very simple and inexpensive.  This is good thing because most commercial stepper motor controller ICs are quite expensive.  This circuit is built from standard components and can easily be adapted to be controlled by a computer.  If you use cheap surplus transistors and stepper motor, the price of the circuit can be kept to under $10. __ Designed by Aaron Cake

Controller provides multiple alarm-driver formats 01/15/98 EDN-Design Ideas Using a piezoelectric element for alarm applications offers low cost, low power, and flexibility.  By coupling this element with a 12C508 programmable controller (Microchip Technology, Chandler, AZ], you can implement an eight-pin alarm generator.  This approach provIdes multiple driver formats with a minimum of additional cost and footprin __ Circuit Design by William Grill, Riverhead Systems, Littleton, CO

Controlling your SLR Camera from an Ipod How to control your camera shutter release from your Ipod (r) or other MP3 player.   __ Designed by © 20142003 Paulo Oliveira'

Convert Atari-style joystick to PC joystick port Some games are easier to play with digital joystick instead of analogue type.  Unfortunately PC has only analogue joystick connector, which makes it impossible to connect normal digital joystick to it.  But with a little adapter circuit, it is possible to use Atari style digital joystick with IBM PC joystick interface.  The circuit adapts the joystick connectors and converts digital joystick movement signals to analogue signals __ Designed by Tomi Engdahl

Convert DAC's outputs from single-ended to differential Mode 06/08/06  EDN-Design Ideas This design suits low-end ac applications or high-precision level-setting applications that rely on a single-ended current-output DAC __ Circuit Design by Liam Riordan, Analog Devices, Limerick, Ireland

Correlating software & analog outputs in a CAN Controller Application Note__ Aligent

Creating a Security Wiring for an Alarm using a PIC16c508 Scroll to find this circuit #10 -When designing an alarm project, the wiring between the sensors and the control panel must not be able to be cut otherwise the alarm system is useless! Making the wiring FULLY SECURE is very complex but a simple way to prevent the wires being cut or joined together (without detection) involves a line-sensing feature called LINE REVERSAL __ Contact: Colin Mitchell

Current-Limited DC/DC Converter Simplifies USB Power Supplies DN252 Design Notes__ Linear Technology/Analog Devices

Current-mode instrumentation Amplifier enhances piezoelectric accelerometer 11/23/06 EDN-Design Ideas Circuit suppresses capacitively coupled noise pickup by piezoelectric sensor and its wiring __ Circuit Design by Dave Wuchinich, Modal Mechanics, Yonkers, NY

CW ID & Telemetry System We wanted to be able to remotely monitor the operating conditions of the EA4YAF repeater and also provide CW ID.  The idea was to transmit a short 1200bps packet with the telemetry information, just after the CW ID, every 10 minutes.  This is how the system was designed an built.   __ Designed by Roberto Barrios EB4EQA

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Computer Interface:  #'s         A -  B        C -  E
        F -  H        I -  L         M -  P        R  - T       U  - Z

 


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