There are 130 circuit schematics available. Last circuit added on Tuesday, 19 May 2015.

CircuitCategoryDate AddedOK?
Yaesu FT-897 - PC interface (PDF)PC 
RS-232 line monitor and loopback cablesPCJan 26, 2001
RS232C Level ConverterPCJan 26, 2001
PC electrically isolated RS422 interface using SN75176B or MAX485PCJun 20, 2004
PC electrically isolated RS485 interface using MAX487 or SN75176BPCJun 20, 2004
Short circuit protected power supply from PC 12V supplyPCJun 20, 2004
Isolated Full Duplex RS232C InterfacePCJan 26, 2001
RS232 DB-9 switch to flip between two serial portsPCJun 20, 2004
Simple RS232 Level Converter based on a MAX232 including Eagle PCB and schematic filesPCJun 28, 2011
PC-based candle ignitor (parallel port based design)PCDec 07, 2014
PC-Based DC Motor Speed ControllerPCOct 25, 2014
Bell 202 and CCITT V23 Compatible FSK Modem CircuitPCOct 27, 2009
Three Wire RS232 To RS485 ConverterPCJan 08, 2014
PC Audio Signal Generator Using RS232 PortPCOct 03, 2013
Commodore 64 24-bit parallel port interface with 8255PCMar 23, 2003
USB digital I/O extender using a PIC18F14K50PCApr 12, 2014
Transceiver to PC soundblaster interface for digital operating modes (PSK-31, RTTY, SSTV etc)PCOct 07, 2009
Transceiver to PC interface with a hardware DTMF detector and galvanic isolation (PDF)PCOct 07, 2009
PC serial port parastic mode interface for 1-wire DS18S20 and similar 1-wire temperature sensorsPCJun 28, 2011
Small circuit and PCB layout for recording to PC Sound Monitor / Pre-ampPCFeb 26, 2010
Ericsson phone to PC serial port interfacePCNov 29, 2002
Magnetic card reader to PC RS-232 port interface based on a PIC12F675 microPCMay 24, 2010
RS-232 to TTL level translatorPCMay 16, 2010
RS232 to RS485 converter schematic to connect PC to RS485 networkPCApr 09, 2010
RS232 serial to USB converter cable circuit schematicPC 
Mac to HP48 cable pinoutPCSep 10, 2006
Game boy camera PC serial interfacePCSep 13, 2006
300/1200 baud BAYCOM MODEM (revision and improved)PC 
HAMCOM (SSTV, RTTY, FAX...) modem using PC-speaker for TXPC 
PTT and/or soundcard interfacePC 
PTT and soundcard interface for the TM255/455PC 
HAMCOM (SSTV, RTTY, FAX...) modem using serial audio for TXPC 
HAMCOM & SoundCard MODEM using serial- or soundcard audioPC 
TM-441 9600bps packet modificationPC 
Using a PC power supply as a benchtop power supplyPC 
Computer Controlled Frequency Counter/Logic ProbePCSep 01, 2009
Circuits to computerize your room/housePCSep 01, 2009
Simple Parallel (Printer) Port InterfacePCSep 01, 2009
The KD2BD Pacsat ModemPCJul 10, 2002
SWTP PR-40 Printer Interface SchematicsPCSep 10, 2006
A Serial Infrared Remote ControllerPCJan 26, 2001
General purpose ISA interface card for PCPC 
PC ISA Card Random Number GeneratorPC 
MIDI cable for Sound Blaster cardsPC 
PC ISA board containing a Z80 microprocessor (coprocessor card)PC 
Analog Signal Acquisition for PC Printer PortPCJan 26, 2001
More accurate PC/AT clockPCJan 26, 2001
Getting power from RS-232 interfacePCJan 26, 2001
PC based Frequency MeterPC 
7 segment rolling display using PCPC 
SmartCard PC EmulatorPCFeb 21, 2005
Relay interface add-on board for PCPCFeb 21, 2005
8-way relay interface board for PC parallel printer portPCFeb 21, 2005
Stepper motor controller for PC parallel portPCFeb 21, 2005
3-axis stepper motor controller for PC parallel portPCFeb 21, 2005
PC based thermometer based on Dallas DS1621PCFeb 21, 2005
Connect two CD-ROM drives to one soundcardPCJan 26, 2001
Headphone driving circuit for soundcardsPCJan 26, 2001
Get power out of PC parallel portPCJan 26, 2001
Null Printer AdapterPCJan 26, 2001
PC speaker volume control circuitPCJan 26, 2001
How to get power from PC to your circuitsPCJan 26, 2001
RS-232 surge protectionPCJan 26, 2001
Simple RS-232 serial port buffer circuitPCJan 26, 2001
Get power out of PC RS-232 portPCJan 26, 2001
Sound Blaster Microphone PreamplifierPCJan 26, 2001
Sega 3D glasses interface circuit diagramsPCJan 26, 2001
Convert Atari-style joystick to PC joystick portPCJan 26, 2001
Fake Joystick circuitPCJan 26, 2001
Using the joystick port as general purpose inputPCJan 26, 2001
Connect other circuits to PC joystick portPCJan 26, 2001
Build your own iRDA SIR Transceiver (Dongle) using MCP2120PCAug 27, 2003
GPS receiver (Gamin, Eagle etc) to PC interface cablesPCMar 23, 2003
Z80 Computer circuit diagramPCAug 18, 2009
The Great Z80 Computer ProjectPCAug 18, 2009
Ethernet interface for Commodore 64 computerPC 
i2c-tiny-usb, a simple i2c interface for the usb portPC 
LCD2USB, cheap open source text LCD interfacePC 
TiltStick, a motion sensing device (USB interface to accelerometer)PC 
Building an Infrared Transmitter for Your PCPC 
FM radio for a PIC (uses TDA7000 IC which is now obsolete)PCSep 08, 2009
Serial servo controller for interfacing hobby servos via RS232 to a PCPC 
New and Improved Sound Card Packet Interface tested with PSK31 and APRSPCOct 27, 2009
Sanyo 20EZ monitor circuit diagramPCMar 18, 2003
Simple RS232C Level Converter using TransistorsPCJun 19, 2011
Interfacing Alphanumeric LCD to Parallel Port using Visual Basic 6.0PCMay 19, 2015
Interface LTC1298 with Standard Parallel PortPCMay 19, 2015
RS232C level converters based on Maxim MAX232 or Dallas DS275PCMay 19, 2015
Isolated RS422 adapter for PC serial portPCJun 19, 2011
Simple and easy build RS232C-RS485 converterPCJun 19, 2011
PC Power Reboot Circuit for ATX power suppliesPCJun 19, 2011
Isolated Full Duplex RS232C Interface for a PCPCJun 19, 2011
RS232 Expander - Expands PC's COM port from COM1 to COM1/1 and COM1/2. No active partsPCMay 19, 2015
PC-based ISA data acquisition and control boardPCSep 13, 2006
Linux Infra-red Remote Control (LIRC)PCApr 12, 2001
Build your own MARES dive computer IRIS interface for RS232PCOct 04, 2010
Homebuilt RS232 LCD InterfacePCJun 18, 2003
Homemade Serial to Nokia MBus Interface on a PCB, without using Zener diodesPC 
Machine Independent Parallel InterfacePC 
PG31 GPS RS232 GPS development boardPC 
PG31 GPS RS232 USB development boardPC 
RS232 RS485 USB Converter BoardPC 
CCD linear image sensor to PC parallel interfacePCJun 20, 2004
PS/2 Keyboard Or Mouse based on an ArduinoPCJun 20, 2010
Virtual USB Keyboard based on an ArduinoPCJun 20, 2010
ADMS programming Cable for the Yaesu FT50, VX1 and VX5PCMay 07, 2010
Radio Interface Box for the Motorola Radius GP300PCMay 07, 2010
PG4S programming Cable for the Kenwood TM-V7 and TM-G707PCMay 07, 2010
Laptop Computer Serial Port Power BoosterPCApr 12, 2001
SPDIF RCA to (Optical + RCA) AdapterPCMay 07, 2010
Various sound card interfacing circuit diagramsPC 
Assorted computer interface circuitsPCMar 18, 2003
Apple II/II+/IIe IDE Drive InterfacePCOct 31, 2002
PC based digital thermometer based around a Dallas Semiconductor DS1621PC 
Simple stepper motor driver for PC parallel portPC 
MS-DOS EEPROM ProgrammerPCSep 25, 2009
SB-Bus Drivers Introduction and Circuit DiagramsPCSep 25, 2009
RS-232 to TTL cablePCMay 01, 2004
9-pin null modem cablePCJan 26, 2001
PC Automatic Power-on CircuitPCMay 19, 2015
Circuit for interfacing a relay / solenoid to a PC based on a 2N7000 FETPCSep 01, 2009
How to construct Garmin GPS receiver interface cablesPCMar 23, 2003
Jasmin floppy disk controller schematicsPCSep 13, 2006
RS232 - Lowe HF-225 interfacePCNov 21, 2002
Serial to parallel converter - connect a large number of digital outputs to a PC parallel portPC 
PC parallel port eight DC power switch cam driver two unipolar stepper motors, lights etcPC 
Pic-Plot GPIB to RS-232 converterPC 
Pic-Plot2 GPIB to USB converterPC 
Computer microphonePCJan 26, 2001
USB to parallel port converter using Cypress CY7C68013A-56PVXCPC