June 2012

Digital Insulation Meter

This digital test meter helps you evaluate the insulation integrity of many electrical devices, apparatus, power tools, RCDs and more. It provides a working voltage of 250V, 500V or 1kV and can measure leakage currents from below 1µA to > 6mA. Also it can measure insulation resistance from below 1M up to 999M. Clear LCD display readout, battery operated portable design. The design is an updated version of our Digital Megohm and Leakage Tester described in September 2011 EPE. The design is PIC 16F88 based and free source code is downloadable from our Library.

  INTENDED ONLY FOR ASSEMBLY BY ADVANCED CONSTRUCTORS SKILLED IN WORKING WITH HIGH VOLTAGE CIRCUITRY.

Dual Tracking PSU (Part 1)

A dual tracking PSU offers near-perfectly matched positive and negative rails set by a single control which is ideal for split supply experiments involving analogue, audio, op.amp applications and more. Our linear bench power supply can deliver up to 1.6A from positive and negative outputs with a range of ±0V to 19V d.c. (dual rail) or  0-38V.

Adjustable current limiting is available on both outputs with a digital display (LCD or LED options) for V,I and current limit settings. A separate 5V 750mA rail is available for logic use.  Uses fairly common components and operation details are described in depth. In Part 2 next month, construction and assembly are described.

Solar-Powered lighting System (Part 2)

This all-low voltage design offers much more than many simple ‘solar chargers’ do. It’s optimised to provide stand-alone lighting when there’s no power source, by using a self-contained sun-powered sealed lead acid (SLA) charger and high-efficiency LED lighting. This self-contained solar control unit boasts high efficiency, three stage charging and Maximum Power Point Tracking. It uses a 5W solar panel with 3-stage charging and is ideal for l.e.d. lighting powered by a 12V SLA battery. Details of a 3-LED lamp are also described. Can be controlled by a PIR, switched or by ambient light turn-on. Lamp timer included.  PIC 16F88 powered, free source code available from our Library. Many applications including security or pathway lighting, sheds and more.

Jump Start Part 2

Our new educational series aimed at beginners and students offers a “Quiz Machine” this month, with Circuit Wizard  simulation support – the modern way to design and explore electronic on-screen. Printed circuit boards and constructional details are included to let you build an actual prototype. If you want to learn the basics of electronics design, don’t miss this great new series! More info from www.tooley.co.uk/epe PICOScope Review A comprehensive review of PICO’s latest PC-based oscilloscope, the model 2250 mixed signal oscilloscope that can display analogue and digital waveforms on a Windows PC.

Also in this issue:

• Techno Talk – illuminating trends in the horticultural sector – can LEDs influence flower and crop production
• PIC n MIX – more on an altitude display system and creating a video driver
• Circuit Surgery – in answer to a reader’s question our in-house Surgeon outlines the characteristics of buffers, class AB amps and output impedance. An essential must-read tutorial on analogue design.
• Max’s Cool Beans – discovering ‘genetic algorithms’  in robotic evolutionary learning applications
• Interface – discovering the LM335Z temperature sensor and how to interface it to a PC.
• Net Work – the Interface column – will UK high speed broadband arrive in your area? More Internet trends including news of the latest ultrabooks and a suggested Android tablet for everyday use.