Re: Complete Newbie with some simple questions.
From: Bob Masta (NoSpam_at_daqarta.com)
Date: 12/07/04
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Date: Tue, 07 Dec 2004 13:32:45 GMT
On Sun, 05 Dec 2004 18:38:31 GMT, "Bishop" <kwayne@new.rr.com> wrote:
>Hi all, I'm a complete newbie here. I'm a VB programmer and could use
>recommendations on what parts I need, suggestions on part makes and models.
>As with most things, I want to keep the price as low as possible.
>
>What I want to do it use a heart rate sensor and a magnetic sensor to record
>heart rate and revolutions when someone is riding an exercise bike. Below
>is a brief illustration:
>
>Hear Rate Sensor and Magnetic Sensor >>> Not sure what stuff I need here >>>
>digital IO board >>> Windows API for the Digital IO board.
>
>A couple other things that play into this:
>1. The Computer with the digital IO board may be a hundred feet or so from
>the bike. I'd like to use cat5 cabling to span the distance.
>2. Eventually I'd like to record data from multiple bikes at the same time
>on the same computer. This is not necessary for the first prototype but
>it's worth mentioning for the parts list.
>
>That's it. I'd appreciate any ideas, thoughts, suggestions!
>
>Thanks, -Ken
>
>
One thing you might want to keep in mind is that almost
every system these days comes with a 2-channel 16-bit
A/D converter in the form of a sound card, and there is a
well-developed API for it. It's AC coupled, typically at a few
Hz or so, but that's fine if you are recording raw EKG and
using the computer to get rate. (I think the QRS complex
that everyone triggers on for rate determination is something
like 1 kHz equivalent.)
Bu I expect you are using the photo-optical blood flow type
of sensor. I haven't used these, but I am sure the pulses
are much broader in waveform. This may not be a bad thing.
If you can arrange to have the RPM be a fairly high frequency
(several kHz) you can use it as a chopper to modulate the
blood signal, then use the computer to demodulate them.
Note that for this technique to work the chopper frequency
has to always be at least twice as high as the highest blood
frequency component you need, so if you are trying to track
from zero RPM you may need an offset. This modulated
signal should have no trouble travelling 100 feet on any
sort of cable.
You would be putting both signals on one wire to
one channel of the sound card. You'd need a second
path for another bike. Scaling beyond that is trickier.
But until you get to needing extra wires, it's the ultimate in cheap!
Just a thought.
Bob Masta
dqatechATdaqartaDOTcom
D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
- Next message: jameshanley39_at_yahoo.co.uk: "Re: how do I push a button remotely (second post)"
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