LJM's Electronics Index

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These pages contain circuits, techniques, ideas and suggestions applicable to a broad range of electronics as well as anything else technical or scientific that I think is worth discussing. Look out - it is growing!

idea Circuit Building Blocks idea

  • A single transistor pump This is a simple circuit that can produce a staircase voltage output given a periodic pulse input. Adding other circuit elements can produce useful devices.
  • The FET as a voltage controlled resistor. Changing the gate voltage of an FET allows the drain-source resistance to be controlled - applications include compressors, oscillators and filters.
  • An optocoupler latch. An optocoupler can be used as an electronic latch (R-S flip-flop) as well as other logical functions.

idea Other Electronics Stuff idea

  • There seems to be a lot of technically poor and often downright wrong information on the net regarding the way that analogue tv works. Surprisingly colour systems seem to be covered well but the basics that apply to both monochrome and colour systems is where things become unstuck. See TV SynchronisationTV Bandwidth.
  • The Philips' Dynamic Noise Limiter (DNL) is a simple but clever circuit useful for improving the sound from noisy sources. The circuit doesn't seem to be currently published anywhere; so here it is!
  • Simple Phasing Circuit - not really a circuit but a way of getting the effect without having to build anything - uses mic, mixer and fresh air to produce the 70s effect.
  • new Analyse the RC circuit. Looks at one of the simplest electronic networks. new

idea Published Stuff idea

Here's a list of things I've already published on paper. I have converted some to HTML versions and I am working on the rest so that they will be available here. I have also taken the opportunity to correct minor errors in the text and add notes but, as far as possible in translating into HTML, I've tried to keep to the 'look' of the original.

  • Audio Compressor. A simple circuit for reducing the dynamic range of an audio signal. An FET is used as a voltage controlled resistor to change the gain of an amplifier.
  • Temperature Stabilisation of LASER Diodes  A circuit that powers a thermoelectric cooler (or heat pump) to control the temperature of a semiconductor LASER in order to stabilise its optical power output.
  • Surface Plotting Program for the HP85. This program (in BASIC) was written for the HP85 in order to plot a three dimensional representation of up to 80 x 80 values (retrieved from a data file). Two alternative perspectives are selectable: isometric or oblique.
  • Computer-Based Characterization of Detectors for Optical Communication. A computer-controlled data acquisition system developed at Essex University to characterize photodiodes and other active optical devices is described. It has proven particularly useful in analyzing detectors for fiber optic communication systems.
  • The Noise Penalty in APD Receivers Operating with Non-Optimum Gain. Using avalanche photodiodes improves the sensitivity of fibre optic receivers; however, operating the diodes at non-optimum gains results in the receivers failing to provide the minimum error rates that they are potentially capable of. Using a simple noise model the effects of gain errors in silicon and germanium diode receivers are calculated.
  • A BASIC Program for Exact Curve Fitting. The program uses a method based on the Lagrange interpolating polynomial. The program given here calculates the coefficients of a polynomial to fit a set of data points such that the fit of the curve to the points is exact.
  • Software Method Generates 5 Bit Baudot Codes. This describes a technique for generating 5 bit Baudot codes (also known as the International Telegraph Alphabet No 2) using a small computer's own serial port; no additional hardware is required. The BBC BASIC program listed here can be easily adapted for use with other machines.
  • Comments on Random Serial Bit Generator. Flip-flops can behave unpredictably if their timing conditions are not observed; this phenomenon is discussed and a solution presented.
  • Slew Rate Control with Independent Rise/Fall Rates. A circuit that limits the rate of change of a signal; a feature of this design is that the positive and negative rates can be different.
  • Uncooled thermal imaging works round the clock. Thermal imaging relies on the infrared radiation given out by all bodies and because it doesn't rely on external illumination is a 24-hour capable technology.

idea Other Stuff idea

  • Make Big Paraboloid Reflectors Using Plane Segments A simple algorithm (downloadable as an Excel spreadsheet) that calculates the dimensions of cardboard sections that when assembled will form a parabolic dish (paraboloid). The design allows free choice of focal length, aperture and overall size. The dish can be used for concentrating energy in the form of sound to make a highly sensitive and directional microphone, or (when covered with a metallic reflector or made from metal sheeting) a solar furnace or a collector for radio waves.
  • Here's something that should be useful: an Everlasting Calendar.
  • Glory be! Photos (taken by me) of GLORIES.
  • My Links list.
  • Is gravity less at the equator and is that why satellites are launched as close to it as possible?


Last updated: 15 April 2006;   Lawrence Mayes, 2000-2006