Computer Interface

This article describes an I-V curve tracer circuit that uses a computer for display and control. The circuit is controlled via the PC parallel port. Software is provided, written in BASIC, to control the measurement and display the results on the monitor...

PC parallel port can be very useful I/O channel for connecting your own circuits to PC. The PC`s parallel port can be used to perform some very amusing hardware interfacing experiments. The port is very easy to use when you first understand some basic tricks. This document tries to show those tricks in easy to understand way...

You usually use PC hardware monitors to keep a close eye on power-supply voltage levels, the speed of system cooling fans, and even the temperature of the CPU. Until fairly recently, this level of system monitoring was reserved for high-end servers running mission-critical applications. However, now that low-cost hardware monitoring ASICs are available, advanced hardware monitoring has become a standard feature in most new PCs...

Using the simple circuit in Figure 1, you can control the light intensity in your room or work area from your PC. The heart of the circuit is a low-power D/A converter that converts digital words from a computer`s parallel port to analog-voltage signals. To isolate the dc low-voltage part of the circuit from the high-voltage part, the circuit uses an optoisolator, which prevents any direct electrical connection between the two sections...

The circuit in Figure 1 is a simple cost-effective waveform generator using PC control. You calculate the digital image of the desired waveform and store it in the 32k X 8-bit RAM (62256) through the 74HCT245 data buffer and the 16-bit local-address bus generator built with the 74LS393 binary counters. The 74LS244, acting like a selection switch, selects the clock input of the binary counter...

This project was begun as a means to charge and cycle NiCad batteries but has become a versatile tool for experiments requiring either a controlled voltage up to +30V and/or a current of +/- 2.5 Amps. If all you want to do is charge and recycle NiCad batteries, then, with hindsight, I`d advise you to buy one of the commerical units available. The circuit I will describe will do the job but it is experimental and has many short comings...

This is a short pointer to some of the available PC based lighting console systems. Most of the software products have a trial available, so I recommend you download several, and spend some time trying to do the sorts of things that you want to do with them. A word of warning: you will find that lighting control packages do different things in different ways, so there will be a learning curve involved, and the more capable the package the bigger the learning curve will be. But do persever, it will be worth it!..

Here is a simple technique for measuring frequencies over quite a wide frequency range and with acceptable accuracy limits using a PC. It follows the basic technique of measuring low frequencies, i.e. at low frequency, period is measured for a complete wave and frequency is calculated from the measured time-period. Cascaded binary counters are used for converting the high-frequency signals into low-frequency signals. The parallel port of a computer is used for data input from binary counters...

It is very interesting and convenient to be able to control everything while sitting at your PC terminal. Here, a simple hardware circuit and software is used to interface a 7-segment based rolling display. The printer port of a PC provides a set of points with some acting as input lines and some others as output lines. Some lines are open collector type which can be used as input lines. The circuit given here can be used for interfacing with any type of PCs printer port. The 25-pin parallel port connector at the back of a PC is a combination of three ports...

Occasionally, a system needs several digitally programmable voltage-output channels. Such output channels typically provide the control for robot positioning, industrial processes, and even home automation...

High-resolution temperature sensing at low cost is possible using only one chip attached to the PC`s parallel port (Figure 1). The Dallas Semiconductor (www.dalsemi.com) DS1722 digital thermometer allows measurement resolution as fine as 0.0625°C in digital form and with linear response. The accuracy specification is only 2°C, but you can improve this figure by careful calibration...

If you have to sample just a few low-rate analog signals, or your PC`s slots are all full or too outdated for the newer data-acquisition products, a simple interface may be all you need. You can build such an interface that requires no external power supplies or adapters (Figure 1). This design is an attractive alternative for applications that require low-rate, portable data acquisition. You can easily adapt the interface for use with a range of sensors, and you can easily create software modules for any application...

You can use the parallel port of your PC and a few additional components to generate a powerful, easy-to-use arbitrary-waveform generator. By using a Visual Basic program with the circuit in Figure 1, you can generate any waveform (for example, sinusoid, triangle, amplitude- or frequency- modulated, or exponential decay) by simply entering its characteristic equation. For this circuit, the parallel port connects to four latches (IC1, IC2, IC5, and IC6). IC5 provides control signals, IC1 and IC6 transfer data to the memory, and IC2 controls a VFC (voltage-to-frequency) converter...

This is a very easy and fun to build project that will allow you to control up to eight external devices through your computer`s parallel port. You may for instance control different appliances such as lamps, computers, printers, tv sets, radios, music systems, air conditioners, air fans, garden sprinklers and anything else you can think of, all through your computer...