Subject:
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Re: Microphone on a Handyboard
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Wed, 27 Aug 1997 13:33:44 GMT
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Original-From:
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Jeffrey Strauss Morehead <MOREHEAD@ECE.UTEXAS.EDUsaynotospam>
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Viewed:
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3362 times
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If you need more than a +200 gain, try an LM358 in single supply mode and
use +5v. These are fantastic op-amps and widely available (Digikey).
jm
On Tue, 26 Aug 1997, Randy Sargent wrote:
>
> > Hi all, has anyone interfaced a microphone to an analog input of the
> > HB? I've amplified the signal with an op-amp (LM386) but can't figure how
> > to integrate the (AC) signal into a usable voltage range for the HB. I
> > don't think that just rectifying the signal will work, but my electronics
> > knowledge is sorely limited.
>
> Assuming you've hooked the LM386's ground to ground and the + voltage to
> 5v, you should be set hooking the output of the LM386 to the analog input.
> Do not insert a capacitor in series, as might be shown for hooking up the
> LM386 to a speaker.
>
> As I recall, the LM386 is pretty cool, because unlike other op amps, it
> tends to center the output signal around half of the positive supply
> voltage if you hook it up straightforwardly. This means that the voltage
> you read from the A->D should be centered around a certain value when all
> is quiet, and you should be able to see samples that go lower and higher
> when there's noise.
>
> Another advantage of the '386 (although not in this situation) is that it
> has a high-current output; it can drive speakers or small motors. One
> disadvantage, though, is that it's maximum gain is 200, which might not be
> enough to get your microphone to make a big enough signal for the analog
> input to measure easily -- depends on the microphone.
>
> If you're not sure if you're getting a signal through to the A->D, try
> blowing on the microphone or clapping right next to it. Both send really
> strong signals.
>
> -- Randy
>
> ----------------------------------------------------------------
> Randy Sargent Newton Research Labs
> Senior Design Engineer Robotic Systems and Software
> rsargent@newtonlabs.com http://www.newtonlabs.com/
>
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Message is in Reply To:
 | | Microphone on a Handyboard
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| (...) Assuming you've hooked the LM386's ground to ground and the + voltage to 5v, you should be set hooking the output of the LM386 to the analog input. Do not insert a capacitor in series, as might be shown for hooking up the LM386 to a speaker. (...) (29 years ago, 27-Aug-97, to lugnet.robotics.handyboard)
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