July 2011

Multi-function filter module

This versatile design can be configured as a low-pass, high-pass or bandpass filter just by moving a few jumper links. It’s ideal as an active crossover in loudspeaker systems.  Learn about filter response characteristics too, using readily-available freeware, in this fully illustrated and informative article that’s perfect for the DIY audio enthusiast.

Metal Locator

This easy to build project is perfect for finding steel frames, studs, bracing and nails in plaster walls.  Helps prevent accidents during DIY. It has a range of approx 1”/ 25mm and can discriminate between ferrous and non-ferrous metals.  Battery powered, ideal for beginners in electronics.

Loop Antenna and Amplifier

You can enjoy tuning in to faint AM stations or  separate close signals using this long-distance AM aerial that’s small enough for use in apartments.  Suits upper AM broadcast band. Varicap diode design.

Beam-Break Flash Trigger

This easy to build “light beam” accessory is ideal for our Time-Delay Photoflash Trigger (February 2011) or can function (with some limitations and/ or modifications  – see article)  as a stand-alone light-beam trigger for a flashgun (does not operate the camera shutter). It employs an invisible infra-red beam to operate an external flash when breached.  In darkness the beam can be well over a metre long.

Converting Uniden scanners for AIS

How to attach a ‘Slim Jim’ antenna to a popular scanner using some warranty-breaking modifications.  Construction of a cheap but effective J-Type IM aerial is included.

Teach-In 2011 (9)

Digital-to-Analogue and Analogue -to-Digital conversion. Our marathon educational series for beginners continues with a look at ADCs and DACs, demo’d using PC on-screen simulation software.

Also in this issue:

• Circuit Surgery  – everything you need to know about driving light-emitting diodes properly in series and parallel.
• Practically Speaking – our workshop series introduces analogue and digital multimeters for the hobbyist.
• Net Work – the Internet column – home area networks, Domotics home automation  and the Sony SMP-N100 home media server.
• Techno Talk – the aftermath of the New Zealand earthquake and strange phenomena surrounding quakes.