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A fourteen inch color CRT available in either kit or chassis form can be purchased with a switching type or linear RGB video amplifier. Costing $550, the Spectrum-14 from Wells-Gardner Electronics has 720 horizontal pixels by 408 vertical pixels resolution. A photograph of the CRT is included.

AT&T's new 32-bit Unix microsystem provides the hardware, operating system and development tools for designing a 32-bit microcomputer. The microsystem consists of six 32-bit ICs, including the WE 32100 CPU chip, a version of Unix for the chips, a clock chip, a development system, a microprocessor-evaluation board, and software-generation programs. The specific functions of each chip, present and future availabilities, and prices, are included. A photograph of the microsystem supplements text.

MITS Inc., the producer of the Altair, had four founders headed by H.E. Roberts. The company's first products revolved around model rocketry. MITS relied on Popular Electronics magazine for much of its product promotion. The company introduced the Altair personal computer in January of 1975. List price for the computer kit was $397. The Altair was the first personal computer and a milestone in the industry. A photograph of the Altair is included.

In the early 1960s it was very difficult for hobbyists to build computers . The Amateur Computer Society (ACS) was started in 1966 with 110 members. Early hobbyists spent an average of $2100 on the construction of their computers. The first advertisement for a microcomputer based on a microprocessor appeared in March 1974 for the Scelbi-8H. Scelbi Computer Consulting later became a computer literature publisher. A photograph of Nat Wadsworth and the Scelbi-8H is included.

The first home computer kit, the Mark 8, came out in 1974. In 1975 personal computers were called hobby computers. The Altair and other computers preceded Apple into the personal computer market. The original Altair cost under $400 and came with 256 bytes of RAM. A photograph of the author is included.

In the early days of microcomputers it was very hard and expensive to build a computer from a kit. Most early microcomputer companies were small and made little money. Early computer shows were verly different and very little software was available. A photograph of the First West Coast Computer Faire is included.

Scott Adams is the founder and president of Adventure International, one of the earliest software houses. His love of computers always centered around games and his first major program was a tic-tac-toe game. He wrote a space war game for a kit computer in assembly language that was a precursor of the Asteroids game. A photograph of the author is included.

Robots are approximately at the same stage that personal computers were seven or eight years ago. A series of robot kits called Movits are being imported from Japan. The fifteen models range from simple mechanical movements to programmable movable robots that can sense their environment. The Movit kits come with good instructions and are easy to use. Photographs of Movits are included.

The Model SK-1 splice kit from TRW includes all that is necessary to perform fiber-optic splices in the field. With portability in mind, the kit features ten splice modules, a splice assembly tool, a 30X microscope, and UV optical adhesive. The kit is priced at $385.

Telmos Inc. has developed a kit by interconnecting and bonding CMOS and DMOS devices on a gate array. This forty-pin IC kit can serve as a prototype for semicustom logic with low-voltage inputs and high-voltage outputs. A photograph shows the IC kit.

Zodiac, from SGS Semiconductor Corp. of Phoenix, Arizona, is the first cell library that offers a mix of analog and digital bipolar cells. Available in kit form, thirty-four cells are provided. It is an extremely cost-effective approach when designing medium to large quantities of chips. The Zodiac process, which lasts from twelve to sixteen weeks, consists of three steps: 1) the customer breadboards the design, 2) SGS then lays out the part on silicon with the selected cells, 3) the chip is then diffused, packaged, and samples are delivered. A table of typical cells that are included in the kit is provided.

The latest kit computer from the Heath Co., the ET-100 Learning Computer, is a 16-bit system designed to aid users in learning the fundamentals of 16-bit microprocessors and assembly language programming. The main logic board, which incorporates the Intel 8088 microprocessor, and the detached keyboard both come pre-assembled, while the breadboard, which can be used for experiments, the keyboard logic, and the power supply must be assembled. The list price of $999.95 does not include a video monitor or cassette storage, though a TV set and standard cassette tape recorder can be used. The ET-100 is an excellent learning tool through which the user can gain an in-depth understanding of the widely-used 8088 CPU, as well as the basics of hardware interfacing to a microprocessor. (Illustrations accompanying the article show technical specifications of the ET-100, a photograph of the assembled system, assembly language routines, and a diagram of a circuit used to interface the 8088 to an external data display.)

There are numerous floppy disk head cleaning kits available. Types of cleaning kits are dry, wet, and wet-dry. The price ranges from $12.50 per kit (Verbatim) to $75.00 (Compu-Clean). All kits clean the read-write heads in thirty to sixty seconds. Disagreement exists as to the frequency of cleaning and the use of the kits at all. A table comparing the various kits available and a photograph of a wet-dry kit are included.

Optical data communications appears to be developing more in Europe and Japan than in the United States when it comes to short-range free space links between computers and peripherals. An experimental infrared joystick controller interface can be built for the TRS-80 Color Computer. A new class of semiconductors has been developed at Sandia National Laboratories in New Mexico. It consists of layers of different semiconductors with lattice mismatching to give increased output and new possibilities. Drawings show range calculations for infrared data links and for the strained-layer semiconductor. Circuit diagrams are provided for the infrared joystick link.

An interface between a TRS-80 microcomputer and a cassette tape player can reduce wear and tear on the hardware and give an audio output. The TRS-80 has an internal reed relay line which can make sound but should not be used because it will wear out. A circuit diagram and a parts list are provided.

A solderless breadboard is the main feature of the Heath ET-100 microcomputer. This is ideal for testing prototypes, or functions that may enhance a system currently in operation. Including 32K bytes or ROM and 16K bytes of RAM, the ET-100 provides for a video monitor and cassette storage. It is priced at $999.95 in kit form or $1499.95 assembled.

Low-level radiation can be detected by several of the commercial dosimeters available. Dosimeter Corporation's MiniRAD-D, the MiniCon, and the Direct Reading Pencil Dosimeter are some examples. Less sophisticated measurements can be done with homemade electroscopes. These require no electronic components. Sources of low level radiation are mentioned for experimental purposes. Photographs of commercial dosimeters and drawings of homemade instruments are included.

A small circuit can be added to the Timex-Sinclair microcomputer to eliminate noise and drop out from the cassette tape memory system. Part of the difficulty results from the fact that various brands of tape cassette players are used. Construction and use of a device called the 'Z-Dubber' is covered. Circuit diagrams and parts list are given plus a source for the device in kit form. Oscilloscope images are shown to illustrate the signal pulses.

A simple electronic circuit can be added to a digital clock to sound an alarm when its power supply is interrupted. This can alert someone to the fact that the clock is no longer giving the correct time. A circuit diagram and parts list are included. Brief circuit operation and construction tips are provided.

Sometimes in electronic circuit adjustment or troubleshooting it is necessary to read voltages in more than one location. A multiple test-point monitor can be constructed to measure four test points. Circuit diagrams and a parts list are included, as well as brief construction directions.

The TRS-80 Model II microcomputer can become a computerized dialing machine with the addition of a little hardware and software. The system can dial any number from its computerized phonebook. A circuit diagram and parts list are provided for the hardware. Program listings show the two BASIC and one machine language programs necessary to run the system. One program is a report generator for monthly calling records. Use of the system is explained as well as modifications for different dialing speeds.

The usual troubleshooting equipment can tell that a certain signal path is bad, but a more precise location of the problem can be had with a short-hunter device. This simple home-made instrument tests for tiny voltage gradients and lights up one of two indicator LEDs depending on which of two test probes has the higher voltage. The circuit diagram is provided plus basic procedures for using the short-hunter.

Ultrasonic sound is utilized most for object detection and range- finding. The Polaroid Corporation uses an electrostatic transducer which doubles as an ultrasonic speaker and microphone to sense distances. This circuitry is available as the Ultrasonic Ranging System Designer's Kit. This range-finding technology is being used in products other than cameras. The LM3905 is an IC timing chip of advanced design over the older but more familiar 555 chip. By the 1990's, the fire volt logic system will have been replaced by lower voltage systems or a lower voltage standard. New support and interfacing IC chips are being announced for microprocessor systems.

Water leaks or moisture increases can be detected by a circuit built around the National Semiconductor chip LM1801. This battery powered alarm chip has a built-in low battery signal for sounding when the voltage of the nine volt battery drops below six volts. The battery should normally power the device for one year. The alarm senses moisture increase because of lowered resistance between two probes, and when resistance reaches 500,000 ohms, the alarm sounds.

A simple piece of test equipment can be made of DIP switches soldered between a wire wrap socket and a DIP solder socket. This device can then be plugged directly into a circuit board, and the DIP component and the circuit can be tested with various pins being turned off or on. This device can save time and trouble in designing, debugging, and troubleshooting circuitry using ICs.

The basic circuitry of an electronic flash unit is explained. The importance of caution is stressed for working with the high voltages involved. A single-shot flash circuit is explained. An automatic repeating flash circuit is explained. One application is a small portable flasher for bike riders or hikers.

The direct memory access (DMA) controller chip of the 16-Bit microcomputer is explained in detail. This chip allows peripherals to communicate directly with memory without going through the microprocessor buses. This chip (8237A-5) has four separate channels with a priority ranking. One task done by the DMA is to refresh the computer system's RAM memory. Several clear diagrams make the text readable. A schematic of the computer's power supply system is included.

The video display of the Timex-Sinclair microcomputer can be improved by having a direct cable input to the monitor rather than the radio frequency (rf) generator. It can also be improved by the same device by having a reverse switch built in to reverse the image at will to white letters on black, or black on white. Complete plans are given for this simple two-by-three-inch circuit board to be mounted inside the computer with the reversing switch protruding on the side of the case. The circuit is available also as a kit. By adjusting the values of two resistors, one can also change the size of the pixels making up the characters to improve the appearance of the characters.

A telephone circuit with at least one touch-tone phone can be made into a put-on-'hold' system with optional music during the 'hold'. The device is attached externally to the phone (on the line). It is operated by pressing the * (asterisk) pushbutton and hanging up within five seconds. The 'hold' ends when any phone on the local circuit is picked up. Music can be provided by a tape deck or by a low power radio. Circuit operation, diagrams and construction are covered.

Measurement of random pulse length is usually done with a storage oscilloscope. An instrument can be made which uses a crystal controlled frequency counter which is turned on and off by the pulse. The counter reads out on an LED display of three digits, but a six digit count can be read by switching to the three most significant digits. The circuit operation is explained. Maximum signal strenth can not be over fifty volts. Construction is covered briefly but full diagrams and parts list are shown.

This is a project to build a low-cost device which converts microcomputer digital signals into the analog signals of the outside world. The device can become part of an audio-signal processing system, an A-D (Analog to Digital) convertor, or a waveform generator. The heart of the device is the DAC1000 integrated circuit chip. Diagrams, parts list, and brief software for controlling the circuit are included. There is also a special section on the 'Basics of D-A Conversion,' plus a section on the DAC1000 convertor chip. Applications of the device include simple testing of digital and linear devices, amplification of music and other sounds, and regulation of motor speed, temperature, or pressure.

This project explains how to build a security communications device which operates through the electric power lines within a building. This transmission system can also function as an intercom or music distribution channel. The common electrical wiring of buildings often has noisy signals, so this device is designed to operate by FM. Simple contact switches can be used to signal when doors or windows are opened. The transmitter only produces a thirty milli- watt signal, but several hundred feet of wiring can be carried. Full instructions, diagrams, parts list, and source for complete kits are included.

The simple circuit described here is intended to be a better active voltage source than the alkaline or mercury battery cell often used. It is constructed of a zener diode, an op amp and several resistors and runs off of two nine volt cells. This active reference circuit can be used in regulated power supplies to produce the effect of odd-valued zener diodes.

Circuitry can be constructed for high precision speed control of direct current motors. The application with the most promise is in robot control, but any situation where direct current motors are used can be benefitted. The basic principle of operation of the controller is pulse-width modulation. Basic types of electronic amplifiers need to be reviewed to understand the controller. Circuit diagrams are shown for amplifier theory and for the schematic of the controller. Drawings show pulse-width modulator waveforms. A photograph shows the complete system.

Zenith Data Corporation has produced a new family of dual-processor microcomputers. The 8-bit and 16-bit machines are available also as kits, and the display screen can be a monochrome version or can be upgraded to color. The 128K main memory is expandable to 768K RAM, and there are dual 320K five inch floppy disk drives. The monochrome graphics feature gives TV quality picture resolution. Photographs show the external front, rear, and internal views of the model 120. A table gives technical specifications.

A programmable voltage-controlled oscillator (VCO) can be constructed which is able to program any waveshape up to the limits of its resolution. The device consists of the VCO, a six-bit counter, memory, keyboard, and digital to analog converters. The process of creating a waveshape begins by sketching it on a thirty- two by sixty-four graph. A square wave is generated, and each of its thirty-two parts is separately assigned a voltage to create amplitude at that part of the wave. The generator can be used for a variety of applications including music synthesis and for any device using voltage control. Circuit diagrams are provided for the VCO and a power supply. A block diagram shows the entire system.

A data acquisition system can be had by combining a homemade data convertor with a microcomputer. The device outlined here has a special interface device to work with an Apple II microcomputer to capture waveform data or send it out to other devices from a digital to analog convertor. The operations can be called from BASIC language programs. Circuit diagrams of the main data convertor and the interface adapter are shown. Drawings show printed circuit layouts and component arrangements. The article continues with the August, 1983 issue.

This brief project shows how to use VMOS FET's (Field Effect Transistors) as digitally controlled variable resistors. A digital-to-analog (D-A) convertor is combined with a VMOS FET in a simple circuit which varies the input to the transistor's gate. The D-A convertor can be made up of a resistor ladder network or a single chip D-A convertor can be used. The circuit can be used or tested without a computer by using a counting chip such as the 555.

This article is for the person who wants to get some basic experience with the new VMOS power transistors. After basic practical information on the device, the author gives instructions to build VMOS amplifiers, VMOS analog switches, and VMOS as variable resistor devices. An actual audio amplifier is shown that is made from one power transistor, one condenser, and four resistors. One retail outlet and several manufacturers are listed as sources for VMOS power transistors. Several books and articles are mentioned as sources of more information.

The electronics hobbyist can add this project to an uncalibrated oscilloscope to make it much more accurate. The increase from about three per cent accuracy to 1000 times that is the aim of this circuit, which is also available in kit form for about thirty-five dollars. It is based on an oscillating crystal and decade divide-by chips. The theory behind the device, plus information to adapt the plan to differing scopes, is given. Construction is simple enough as to receive only one paragraph of comment.

This article is for someone with a certain amount of computer electronics background who wishes to learn about 16-bit technology. By studying a microcomputer building project based on the Intel 8088 chip (the same chip used in the popular IBM-PC personal computer) one can learn such technology and have skills which are relevant to the trends in microcomputer hardware. The basic hardware system covered here is available in a kit for $400, and includes a 64K motherboard and RS232 serial interconnect. One can add on peripherals to build a complete sophisticated state-of- the-art system. Detailed circuitry is drawn out and discussed, but the article is definitely not for the beginner in computer hardware. Future parts discuss the circuits in more detail.

The article tells the hobbyist how to interface computer game joysticks to a computer very simply and inexpensively. Using an integrated circuit chip called a dual non-retriggerable monostable vibrator, costing less than one dollar, one can build a small circuit and add about seven lines of assembly language to control it. It works by converting the position of the joystick to a length of time which is measured by the brief program. Basic mathematics of operation are shown as well as a table of experimental results. Part Two of the article shows a second way of building a joystick interface. It uses an A-D (Analog to Digital) convertor originally designed for automotive use. This chip when built into the given circuit will translate joystick position into a binary number.

This is the second part of a project to build a sophisticated thermometer which is controlled by a microprocessor and an Electrically Programmable Read Only Memory (EPROM). A description of the program (algorithm) used to control the device is given and explained. Details of construction, testing, and calibration are given. Also given is a source for the complete kit or sections of the device. The EPROM is available in preprogrammed form. An operation and use section is followed by possible applications for this intelligent device.