TeleHealth Stethoscope

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TeleHealth Stethoscope

Postby chenj » Thu May 29, 2008 10:40 am

I'm a student working on building an stethoscope to use on the measure activity. I'm connecting a mic to an LM324 to amplify the signals. Should I have connect the mic and amplifier in series or parallel? or should the mic be connect to a separate USB for power? For the LM324, what do I connect to the V-, V+, and the Vcc?
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Re: TeleHealth Stethoscope

Postby ektoric » Thu May 29, 2008 1:36 pm

If I remember correctly, the Measure activity will take input from the Mic In audio jack. You may need a mic that converts the stethoscope audio signal to an electrical one that can plug into the Mic In jack, but I'm not sure you need an opamp in the middle for amplification.
Code: Select all
Stethoscope -> mic -> MicIn.

If for some reason you did want to amplify the signal, it would indeed be in series that you need to connect them.
Code: Select all
Stethoscope -> mic -> opamp -> MicIn.

The reason why you probably don't need it is because what you would be amplifying would most likely be the noise from the mic stage more than the signal from the steth stage. I would suggest getting a more sensitive condenser / mic.

As for getting power from USB, check out the USB spec to see how to tap the power from a USB jack. Remember that the XO is a lower power device and just barely meets the USB power specifications if I remember correctly.
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Re: TeleHealth Stethoscope

Postby mattd » Thu May 29, 2008 6:47 pm

I can't add to what ektoric said, but you may want to post your question over at http://www.olpcnews.com/forum as well. There's some tech-heads over there that may take interest in what you're doing.
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