Everyday Practical Electronic July 2007

Video Reading Aid — displays enlarged text on a TV or video monitor . Our electronic aid is designed for those having impaired sight or those who just want to make life a little easier for themselves. It combines a small monochrome CMOS TV camera with a videoprocessor, which boosts the contrast and allows users to select either a positive or negative enlarged image on a TV or monitor.

All details are contained along with full photography in our ten page constructional article. Uses an SMT chip. Good soldering skills and dexterity are desirable for assembling this project.

Digi-Flash Slave — this opto coupled slave flash drive can help you radically improve the results from flash photography, by using a second 'slave' flash triggered by your camera's built in flash. A simple way of enhancing indoor photography or portraiture.

MiniCal 5V Calibration Standard — How accurate is your digital voltmeter? Find out with this simple yet accurate DC voltage reference. If your meter fails the grade, the reference can be used as the calibration standard too.

As a bonus, a crystal-locked frequency reference is included that doubles as a crystal checker.

Specification:
5.000V ± 0.02% voltage standard
192.3mV ± voltage standard (optional ±0.1% or ±0.04%)
Two ±0.1% resistor standards (optional ±0.01%)
Crystal locked frequency reference
Crystal checker.

Lead-Acid Battery "Zapper" — a simple circuit designed to extend the working life of liquid electrolyte lead acid batteries, by dissolving the lead sulphate crystals that form on their plates.

The circuit is powered by the battery itself or by a charger, and "zaps" the battery with a series of high voltage pulses. It may sometimes rejuvinate some batteries that have sulphated due to lack of use, however it cannot possibly rejuvinate a battery that is simply worn out.

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