Monitor your PC with an analogue meter

Dave Barton shows you how to use an audio signal to monitor anything you like on a retro analogue needle-meter.

Okay, we know what you're thinking - haven't we already done this guide? At first glance, it might look eerily similar to our analogue hard drive meter guide, but this issue's guide will show you how to do much more with an analogue meter.

While the previous guide showed you how to monitor your hard drive's activity with a simple on or off signal, this guide will show you how to monitor pretty much anything on your PC using a variable signal that's perfect for an old-school analogue needle.

Of course, there are guides on the Web that show you how to do this using pulse width modulation, PIC micro controllers and various other fancy gubbins connected to custom USB interfaces. However, such methods are complicated, not to mention expensive.

Conversely, the method we explain in this article offers similar results but dispenses with the scary electronics and programming.

Instead, it uses a plain audio output to drive the meter - just like an old-style vu meter. With the help of some nifty volume-controlling software, you can move the gauge to roughly any part of the scale to show your CPU load, download rate, CPU speed or whatever you fancy.

At the moment, the Windows software used (programmed by yours truly) only monitors CPU load, but I plan to add more features at a later date.

What you need:

•    A 1N914 signal diode (Maplin, part number QL71N - 16p)
•    A 10uF capacitor (Maplin, part number VH07H - 12p)
•    Selection of various resistors, or a 22k potentiometer (Maplin, part number JM72P - 69p)
•    An analogue panel meter - any salvaged voltmeter or vu meter should be fine (or Maplin, part  number LB80B - £4)
•    Pieces of wire
•    Soldering iron and solder
•    Breadboard
•    Heatshrink and heat gun
•    A 3.5mm audio jack plug
•    An unused audio source

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