I would use a LM331, Voltage-to-Frequency converter.

On 21 Feb 2002 at 11:00, Martin Peach wrote:

> A CMOS 555 works well, temperature drift may be an issue. The input voltage has
> to be kept in the 1/3 to 2/3 Vcc range. You can get very high resolution on
> slowly changing signals such as temperature by counting for longer. Accuracy
> depends on the linearity of the VCO transfer function, which can be corrected
> for if necessary. For higher sampling rates measure the width of single pulses.
> /\/\/\/*=Martin
>
> ----- Original Message -----
> From: "marco genovesi" <marco.genovesi@LIBERO.IT>
> To: <PICLIST@MITVMA.MIT.EDU>
> Sent: Thursday, February 21, 2002 10:36 AM
> Subject: [EE]: A cheap A/D interface
>
>
> > Hi all,
> > I have to interface my 16F84 Datalogger ( 4.5V supply) with sensors that
> > have a voltage output, but in my board I have only one free pin (RA4), so I'm
> > thinking to a voltage-frequency converter. I need 8 bit resolution. For a lot
> > of reasons, I would like a really cheap solution, preferably not over 2-3$. I
> > have seen that a 4046 CMOS has a voltage-controlled oscillator, but I haven't
> > never used it: can it be an acceptable solution for my specs or
> I'm
> > going in a wrong way? Have anyone any suggestion about 4046 VCO use or
> other
> > low cost alternatives?
> > Thanks in advance
> >
> > Marco
> >
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---
Marcelo Puhl
Mensa Brasil member
http://www.mensa.com.br

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