Vacuum Tubes Valves
Musical & effects
Yagi Uda Antennas
Metal Detector Circuits
Liquid Sensing Circuits
Light Sensing Circuits
Voltage Detector Circuits
Air-Gas Detection Circuits
Human Sensing Circuits
RF & Radiation
Optical Sensing Circuits
Free Energy Circuits
AC to DC & DC to DC
Solar Cell Circuits
Micro Power Circuits
Switching Power Supplies
Light Laser LED
Digital to Analog
Analog to Digital
Data Bus Circuits
Voltage to Pulse
Current to Voltage
Frequency to Voltage
RF Converter Circuits
Sine to Square Wave
Voltage to Current
voltage to frequency
Period to Voltage
Video Wall circuits
TV Video Circuits
Motor Control Circuits
8051 / 8052
PCB CAD Software
Car bike Circuits
555 Timer Circuits
Remote Control Toy
H Bridge Circuit
DIY HV Variable Cap
DIY PMA alternator
Interconnection & Timing
Digital Signal Integrity
Digital & Bipolars
Sensors & Detectors
Regulated Power Supply
4 Band Resistor
5 Band resistor
6 Band resistor
TWO TRANSISTOR RS232 TO DREAMCAST CONVERTER
A simple circuit to connect the Dreamcast console to PC. No MAXxxx IC required. Only a few discrete components. This circuit is a direct replica of the daVinci cradle schematic:
Centronics port D/A converters and low-pass filter
I keep all rights to those circuits myself. You may freely build those circuits to yourself and your friends, but commercial use of those circuits is not allowed. NOTE: Those circuits are old designs from time when I was not so good in electronics than I am now. All of the designs are not very good and I would do those circuits today differenly....
ESD Testing for RS232 Interface Circuits
The machine model, commonly used for ESD testing in Japan, is a more severe ESD test. This model simulates metallic contact between the device under test and a charged body. The source capacitor is 200pF with no limiting resistor. The higher source capacitance and the absence of a limiting resistor causes the device under test to be subjected to...
Hot Swapping the PCI Bus
The circuitry for a hot swappable PCI slot on a motherboard or backplane is shown in Figure 1. The power supplies for each PCI slot are controlled by an LTC1421 and four external FETs, and the data bus is buffered by several QS3384 QuickSwitches or equivalent. A PCI power control ASIC, FPGA, microprocessor or the like, controls all of the slots...
Serial port controlled infrared transmitter with PIC
This is a programmable infrared (remote control) transmitter, which can be controlled from a PC serial port. It is capable of sending many remote control formats, including the Philips RC-5 standard. Exact formats with the timing parameter names are shown on the pictures:
A Serial Infrared Remote Controller
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...
Schmitt trigger with LM741 op-amp
The schmitt trigger circuit is built around a single LM741 op-amp, its output buffered by a transistor, which in turn energizes a relay. The relay may be replaced by a red LED if desired. The LM741 may be replaced by a LF411 or other JFET input op-amp with better slewing characteristics.
ADC interface conditions high-level signals
Designers who build equipment for the industrial market share a widespread problem. At one extreme, they must build equipment that supports ±10V bipolar voltages, often riding on a high common-mode level, a requirement enforced by 30 years of legacy industrial equipment. At the other extreme, the analog signal needs conditioning to match the...
USB Microphone Line Level Preamp
The computer needs at least 180 millivolts peak-to-peak and the condenser microphone in my headset produces about 20 millivolts peak-to-peak into a 2.2k load with normal speech levels. There are USB ports on the machines, so I can use that for +5 volts. After a quick look in my parts boxes, I decided to put the input jack and output plug on the...
RS-232 to TTL cable with MAX232
Here is a diagram of the internals of the MAX232A. It shows a double charge pump voltage doubler and a +10v to -10v voltage inverter. The voltages output are used to generate the RS-232 compliant signals. The MAX232A has provisions for two serial ports on the same physical package. Most people only connect one of them. You can get a data sheet...
PC speaker volume
This simple circuit can be used to control the volume of PC speaker. The volume can be adjusted to any value between total silence and full volume.
Null Printer 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. Usually many home-made circuits use parallel...
Ham radio Communication
Its a very easy interface to build an requires only a few £/$ worth of components. A you can see by the picture on the right, there`s not much to it. To be honest, the pictur is misleading. This hamcomm interface has an added `extra` facility. The original hamcom interface was RX (receive) only. This one has a TX (transmit) bit added on so that...
Sound Card Interface with Tone Keyer
This is an improved version of the audio interface commonly used to connect a computer soundcard to a transceiver`s receive and transmit audio circuits. This kind of interface is used by computer programs that send and receive SSTV, RTTY, CW, PSK31 and various other digital modes entirely in software.
Adaptor for the Dreamcast serial port
This page describes how to build an adaptor for the Dreamcast serial port that will allow you to connect it to any computer using a standard 9-pin DSUB connector. The main component is a MAX voltage converter, since the Dreamcast serial port uses CMOS (3.3V) voltage levels, whereas normal RS232 uses +/-12V levels.
PC PCB Drill
This project`s purpose is to design a fully automated machine for drilling a printed circuit board, (PCB) blank at a minimum cost and with the minimum amount of custom machining. This low cost philosophy is achieved by adapting the existing mechanical assemblies from readily available computer peripherals and electronic measuring instruments....
Power from PC parallel port
PC parallel port was never designed to provide any output power to divices connected to it. it was only designed for connecting printer to your PC. But in this weird PC business everything changes. Suddenly the parallel port have become a port where you can connect very wide selection of devices like software protection dongles, removable disks,...
Turn an old PC into a multi-channel pulse generator, for PWM/servo/stepper
PulsePar turns a PC into a multi-channel pulse generator utilizing the parallel port. The period, duty and phase of each channel are adjustable so as to be used in PWM systems as well as in testing servo and stepper (stepping) motors. If you have an old PC, boot it by dos to run PulsePar and control it by SeriCon on your GUI PC through serial port.
RS232 to RS485 Converter
The project we have chosen as our example is an RS232 to RS485 converter. This is a often needed device which can demonstrate a lot of principles of circuit design, and hopefully the finished project will be useful to some people, just as it stands. Without meaning to confuse the issue, we also have available a second, more up-to-date 232-to-485...
USB sound card with PCM2702
If you use great IC PCM2702 from BURR BROWN / Texas Instruments you can create a fully functional USB sound card. This sound card can be powered from USB port and has one stereo output. You don’t need to install any driver for Windows XP and Vista, because they are already inside. This is really plug and play. The core of this construction is...
Controlling the PC Parallel Port
This source code module provides the low-level control of the port, implementing code to control 12 outputs and read 5 inputs. This code was written for Borland C/C++ v3.1, but you should be able to adapt it for other compilers. You can view the source code online, or download an archive (prn_io.zip) that contains PRN_IO.C and PRN_IO.H. To use...
The Dutch magazine Audio & Techniek once published an article about one-way loudspeakers that were based on Audax units 1. Although speakers using just a single full-range unit per audio channel were disregarded in audiophile circles (high intermodulation distortion), they could also have important advantages (excellent imaging). The editors of...
PC ROM emulator circuit
This ROM emulator improves the easiness to build/use it by reducing down its function which can be used as a ROM emurator. The kind of the ROM types to be emulated, are 2764, 27128 and 27256. The debugging capability is only Load and Run, omit functions such as trace or step execution. It will still sufficient because Load and Run is used mainly...
PC Temperature Meter
This is a four-channel temperature measurmet adapter that works without external power supply. It will suitable for measureing temperature and logging its data with a PC. The circuit diagram is very simple and no adjustment is required, everybody will able to build it with ease. I chose an Atmel ATtiny15L for this project. It is the only device...
Mini PC Digital Oscilloscope
This is a portable oscilloscope adapter that it can be held in breast pocket. Its operation is only sampling and sending to host PC. The most of functions of the oscilloscope are processed by host PC. Therefore, oscilloscope adapter can be simplified. This oscilloscope adapter using a TMP47P242VN 4bit microcontroller for acquisition control. But...
Analogue / Digital Logger II
This is a circuit monitoring device. It runs for over 10 days and can log up to 32k events both digital and analog. Samples are logged either on a timing basis (.01 to 2.5 seconds), or on a triggered basis. Four inputs are provided, up to three of which can be analog. All setup and configuration is done via a terminal program. Once configured,...
Analogue / Digital Logger I
Intermittent failures in electronic systems are some of most difficult to diagnose. This device is designed to run for days at a time looking for a failure and logging the event. The unit is based on a PIC16F84. Six digital data lines are brought in via a 74hc165 shift regiser. The shift register is connected to a set of series resistors so...
Atari joystick to PC joystick adapter
ome 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...
RS-232 Data Switch
This report deals with the design for a small asynchronous serial data switch. The switch architecture allows 14 serial ports supporting a subset of the RS-232 protocol. The requirements for the switch are discussed. The hardware interfaces are described in detail, and the software function is described in the form of a user's manual. Finally,...
PC FM radio
Stabilised tendency of catering: Vcc=9~12V. Frequency of reception: 88~108MHz. Consumption: 100mA. If you know some language of programming as C ++, PASCAL, VISUAL BASIC, DELPHI etc you can write a program which will send in the parallel door (378 I) of PC a number from 0 until 255 checking thus the tendency of expense of simple D/A of...
AVR terminal for serial port
The LCD display is represented by the connector X1. It has a HD44780 compatible LCD controller and I'm using the 4-bit interface to send data to the LCD controller. The LED's are multiplexed. I've seen the circuit somewhere in the web. It is possible to connect 12 LEDs with only 4 tristate ports with this circuit. You can address the LEDs...
250 Watt PC power Supply
Up to 10 A continuous output current, or operation with 50 % ESD and 18 A peak current are possible without a fan if sufficient natural air flow is present and the ambient temperature does not exceed 30 °C. A small CPU fan (40 x 40 mm) should be used for more than 10 A continuous current. The heatsink surface is not large enough to keep the FETs...
USB Interface Circuits
Computer Interface Circuits
Ultrasonic distance finder circuit
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is measured. There are three main categories of distance measurement methods in use: a) By...
Simple Metal detector circuit with CD4030
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to find something potentially valuable, hidden a few centimeters below the soil. So many...
Fully automatic watering circuit for flower pots
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This circuit comes as a solution to this problem. Depending on humidity of the pot at...
Simple deep searching metal detector circuit
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the circuit of this metal detector, it is possible to detect a metal coin in depth of 90 to...
Sub-Harmonic Bass Converter for Electric Guitars
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound, such as filtering or distortion. Instead, a frequency division system produces outputs...
Echo Depth Sounding Sonar for Boats
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the calibration of the rope. This arrangement still exists in some yachts. The big...
100W HiFi Audio Amplifier Circuit
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power supply must be symmetrical so that no electrolytic capacitors are needed at the outlet....
Plant-Pot Water Level Indicator Circuit
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower. The circuit of the device is shown in Figure 2. The water detection is made from the bottom...
Analogue Sound Preasure dB-Meter Circuit
The best human ear can capture sounds from 20Hz to 20KHz. These limits are known to be the broadest that can exist. Normally the normal limits range from 100Hz to about 13KHz and depend on the age and health of the individual. We for our measurements and to have a good accuracy we will get the limits of 20Hz to 20KHz. A sound to be heard does...
DIY HV Variable Capacitor
DIY PMA Alternator Plans
Digital Signal Integrity