[sdiy] strange behavior from an ADC

[Scott Gravenhorst]

Dan,

If you have webspace, it is good to place a schematic of the exact circuit you are
using on that webspace and then post a URL to the image.

If you have no webspace, there are free ones that can be used.

What you really want is for us to look at that schematic - but currently we cannot.

This is especially true if you've taken an example schematic and made _any_
modifications to it.

A picture is worth 1,000 or more words.  It can be difficult for us to imagine what is
on your breadboard without the schematic.  I know it may take some time to draw it out
(even if with a pencil and then scan it), but sometimes the act of drawing it out will
make you see what you're doing wrong.

Dan Snazelle <subjectivity at hotmail.com> wrote:
>
>Ok
>
>i hate to keep asking questions but I think now I have no choice.
>
>The ADC I am using is an ADC0808
>
>It is supposed to take a REF of up to 5volts and a neg volt ref of Grnd.
>
>The VCC is 5volts.
>
>But here is where things go weird.
>
>I built up a few peoples level shifter circuits to try and get to 
>the bottom of my problems. 
>
>So i ended up with a perfect signal that was in between 0-5.
>
>i got nothing.
>
>So i decided to play it safe and hook up a pot between 0 and 5 
>volts and put it through a 1k resistor into the input of the ADC 
>
>
>I got nothing!
>
>So i decided to plug the same pot into 10v to grnd
>
>Well guess what...The ADC only seems to KICK IN (or respond) 
>between around 5.1 volts all the way up to 7 volts. 
>
>faulty chip?
>
>what the heck could be going on?
>
>This does explain all the problems I was having though.
>
>BTW...my 5 volts is coming from a reference and it IS putting out 5volts.
>
>
>
>any help appreciated
>
>
>Thanks
>
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-- ScottG
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-- Scott Gravenhorst
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