April 2010

PIC Water Tank Level Alert (Part 1)

An easy to install measuring instrument with optional remote monitoring using radio telemetry. This advanced design will remotely monitor up to ten storage tanks and automatically control a pumping system. Our PICmicro based system uses a novel pressure sensor technique to measure the tanks’ contents and in its basic form it’s a standalone unit that is located next to the tank. It has zero power consumption unless it is displaying the tank’s contents.

The telemetry version uses a solar-powered battery source and transmits its reading via a 433MHz radio link to a remote base station up to 250 metres away, and can display a variety of data. Radio transmission of level, temperature and cell voltage is possible. Part 2 next month describes construction.

USB Power Injector for External Hard Drives

Some USB peripherals require more power than a single USB port can provide, and some USB ports can’t provide sufficient power anyway, so this USB power injector is just the thing for use with portable USB hard drives. It permits power to a USB device to be boosted by using an external regulated mains adaptor.

LM3909 Replacement Module

The legendary LM3909 National Semiconductor chip from the 1980’s was an enormously versatile bipolar chip that was also very clever, flashing an LED from a 1.5V cell, or oscillating at audio frequencies.  This module offers many of the versatile features (and more besides) of the original LM3909 chip. Application ideas include a micropower LED flasher, a quartz clock motor driver, continuity tester and more. A fascinating little project with many uses.

Alternative 12V 10A Power Supply

This high-power battery backup is a float charger which will also act as an emergency power supply, providing a 12V supply during mains power outages. Originally intended to power a radio transceiver, it will find many practical uses around the home, garage or workshop. Straightforward to build with full constructional details supplied.

Teach-In 2010 Ladder Logic Programming For the PICmicro.

The 6^th and final part shows you how to customise and extend the software, optimising the program code and extending the PLC software.  An 11-page special feature!

Also in the April 2010 issue:

• Recycle-It offers ideas and pointers for salvaging something useful from old tape-based telephone answering machines – a car alarm or model railroad sound effect without needing a complicated voice recorder chip!
• Interface for PC enthusiasts follows up on USB to serial conversion techniques.
• Circuit Surgery – our ever popular in-house ‘surgeon’ gives hints and tips for driving LEDs with a ULN2003A driver chip.
• PIC n MIX introduces the Propeller Processor prior to taking one for a ‘spin’.
• Net Work – the Internet column – a new router is needed, but which brand to buy?