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Author Topic: Sound/heartbeat recording with QB64?  (Read 91 times)


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Sound/heartbeat recording with QB64?
« on: March 01, 2013, 03:49:08 AM »
Hey all,

Is it possible to record sound with QB64? If yes, some info please.

And I also want to investigate the possibility of recording the human heartbeat with QB64.
Two or more, use a FOR!


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Re: Sound/heartbeat recording with QB64?
« Reply #1 on: March 01, 2013, 05:54:37 AM »
Must be possible but depends if you mean QB64 ALONE ::) ::) ::)

The easiest microphone to use would be a piezo ceramic - but these are capacitive so need a ginormous amplifier input impedance  for workingg at low frequencies!
Such amps can be built (try FET with negative feedback)

Nearly all microphones are "velocity type" - the volts depend on the speed at which the sensed surface moves.

If I was doing it, I'd us a capacitance that varies as one of its plates (Skin of your wrist) moves
To get an output (as in Ye Ancient Cobra Phonograph pickup) you feed a MHz signal to it via a diode.
The dc volts across the diode then gives the capacitance at that instant  and is going to work down to zero frequency, as needed.

Now where are we going to feed this signal?
The normal mic inputs feed it to propriety software and won't work at a low enough frequency.
So what we could do is get the frequency UP (from the <1Hz range to 1000 Hz

To do this you heterodyne (add across a diode) the signal of MHZ oscillator 1 (static) and that od MHz oscillator 2 (the one feeding the "to your skin" capacitor (as in the Theremin)
The signal then (tune the oscillators) appears as a KHz signal (suited to normal amps) whose amplitude is the position of your skin (the pulse signal)

If you are a QB64 man, you may not fancy the above part of this project.
QB64 begins when you feed the output of your amplifier  to an array and read it by QB64

I see there is a mobile phone that claims to register pulse rate (and the advance walking stick of Fujitsu). How about pirating their hardware or buying a "broken" one on ebay?.

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