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Contents for Volume 27 No. 5

What's Flat, Shiny, and Exterminates CRTs?

Cheaper and better flat screen technologies coming in now could knock the conventional cathode ray tube for six. Andrew Armstrong takes a look at some of the more promising ones for computer and television use. Part 1 of 2 parts.

An AVR Microcontroller Programmer

The recently-introduced AVR microcontrollers have certain advantages over other types. They can be very fast, and also can be programmed in-circuit. Robin Abbott has designed a new microcontroller programmer for the AVRs based on his experience with PIC programmers.

Fridge Thermometer

Too many people don't know how cold their fridge should be to store food safely, let alone how cold it is. Terry Balbirnie's fridge thermometer/monitor helps to keep the fridge between 2 and 4 degrees Celsius.

"Hush" Noise Reduction Unit

Based on "Hush" technology, Robert Penfold's new noise reduction unit does not require manual setting of the threshold level. The circuit includes stages that analyse the input signal and set the most appropriate threshold level.

UHF Model Radio Controller

UHF radio can be more effective for model control than the old 27MHz band. Geoff Pike GI0GDP decided that "making a UHF radio control system should not pose major problems, given the ease of component availability and new construction techniques", and developed the design featured here.

Fast Fivers 9 - Audible Logic Probe

Low-cost quick circuits from Owen Bishop. This logic level probe based on the 4046 phased lock loop ic enables you to keep your eyes on circuit under test by sounding a high note for a high logic level and a low note for low.

Guardian Light

Emergency lighting systems help people find their way to safety or just sit in peace if the power fails for any reason. The Guardian Light is battery backed and comes on automatically if the mains light fails.

Electronic Timing - Part 1: Basic timing

"The time constant of a circuit is no more precise than the least precise of the components." RC timing circuits can be more accurate than you might expect, as Owen Bishop describes.

Magnetic Swipe Card Reader

A simple ISO track 2 magnetic card reader with PC-based Turbo Pascal software, by Magnus Pihl. Based on the Omron manual 3S4YR-HNR-4U, but applicable to other track 2 card readers.

A 27C16 Eprom Programmer

Running from DOS commands on a PC via a 9600 baud serial connection, Richard Grodzik's compact battery-powered eprom programmer programs a basic 2kB eprom in two seconds.

Practically Speaking

Terry Balbirnie describes this month how an analogue panel microammeter can be re-scaled to read a higher current range.

Mods Mods Mods

Magnetic Swipecard Reader

In the software, the statements:

while I<200 do and if I<300 then print else (etc.)

should read:

while i <200 do and if i<300 then print else (etc.)

This appears to have been introduced by a helpful wordprocessor autocorrect that does not like to see an isolated lower case i.

Audible Logic Probe (Fast Fiver No. 9):

Figure 1, the circuit diagram, should show R3 (10k) between pin 4 of IC1 and the base of Q1. The stripboard layout and parts list are correct.

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Copyright © 1998 A. S. and H. P. Armstrong