From: Robin Hollands Subject: Re: TECH: Hooking a treadmill to the PC Date: 8 Mar 1996 13:07:14 GMT Message-ID: <4hpbe2$9ht@bignews.shef.ac.uk> Organization: Automatic Control & Systems Engineering, University of Sheffield From: Robin Hollands > I have the book "The Virtual Reality Construction Kit", and it >explains how to hook up a treadmil or bicycle to the computer using a >infrared transmitter. I was wondering if any one knew how to use the >magnetic sensors that those bike computers use. > There's info on a number of ways to connect up a treadmill or bicycle in my book "The Virtual Reality Homebrewer's Handbook" due out in a month or so from John Wiley publishers. There's two main ways to a magnet based system to measure rotation. Assuming to have magnets placed around your wheel then you can sense them passing using a Hall effect switch mounted nearby on the frame. The pulses from the switch can then either be connected to a digital counter to provide an indication of distance travelled between readings, or alternatively passed to a frequency to voltage converter chip, which will give an output proportional to speed. If you don't want to mount magnets on your wheel, you may be able to get away with using an inductance based sensor if you can adjust it to signal as the spokes go past (on a bicycle based system). Of course a third option is to use a small dynamo (or motor used as a dynamo) being turned by your treadmill or bicycle wheel. You'll probably have to gear this down (i.e. put a bigger 'wheel' on the dynamo shaft) to stop the output from saturating at relatively low speeds. If you use a DC motor or dynamo, you should be able to output the voltage directly into a analogue to digital converter. Robin (UK VR-SIG Chairman)