September 2013

This month’s highlights

Digital Sound Effects Generator

This inexpensive, compact module can play back up to eight different sound effects, lasting a total of 60 seconds or more. Two trigger inputs, offers 1-8, cycle or random playback.

It can be used in model railway layouts, toys, models or any other projects that would be enhanced by the addition of sound effects. USB interface for programming via a PC. Coin-cell powered or low voltage AC/ DC supply. PIC18F27J53 powered with free source code available from our library.

Surface-mount devices require good soldering skills.

PLEASE TAKE NOTE

It has come to our attention that, while the LM4889 was specified as an alternative to the LM4819 audio amplifier IC, we have discovered that the shutdown pin polarity of the LM4889 is opposite to that of the LM4819 (active low rather than active high). We recommmend that constructors stick with the LM4819.

USB Stereo Recording & Playback Interface

This pro-quality design allows you to produce high quality audio recordings with professional standard balanced microphones or select line input.

Connected to a laptop or PC via a USB cable, our interface unit has twin balanced-input pre-amps with XLR sockets, and enables you to record audio with sampling rates up to 48 kilosamples/ second and provides high-quality stereo analogue line outputs for playback or monitoring. There are also S/PDIF digital audio inputs and outputs. Use of Audacity PC software is also described.

Surface-mount devices require good soldering skills.

Minireg Adjustable Voltage Regulator

A useful little p.c.b. module with an adjustable regulated output rated from 1.2 – 22V > 1A.

Vacuum Pump from Junk!

Every serious techie needs a vacuum pump in their armoury of lab and workshop gear, and this special feature shows how one can be made safely from an old fridge/ freezer compressor. Use them to evacuate potting resin of bubbles, try vacuum packing something or generally experimenting with the physics of vacuums.

Computer Error: reliable digital processing – (Part 2)

A short history of high-reliability computing, continuing with a fascinating account of NASA’s early attempts at triple modular redundancy used on the Saturn V space rocket. (Also see Max’s Cool Beans column this month).

Also in this issue:

Ingenuity Unlimited: Wind-Up Torch
Techno Talk – microfluidics, and the perils of using low quality counterfeit batteries.
Circuit Surgery – our in-house surgeon presents a bumper feature on filters and frequency response, helped by a large dose of LT Spice.
Practically Speaking – our workshop series offers guidance when getting started with test gear.
Max’s Cool Beans Blog – how radiation can adversely affect electronic components and systems