From: Gary Tait
Subject: Re: Need help designing a circuit...
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Date: Thu, 16 Jan 2003 14:50:07 -0500
NNTP-Posting-Date: Thu, 16 Jan 2003 14:52:30 EST
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On Wed, 15 Jan 2003 22:48:10 -0600, "ryanm"
>"Gary Tait" wrote in message
>> The circuit is rather simple too, or findable, just inteface the
>> analog enviroment sensors to the ADC of the micro (choose a micro that
>> has an ADC, or use and external ADC). You could do it is Assembler,
>> C, or even Basic (if the chip you choose has a Basic compiler)
> I know it's as simple as: probes -> controller IC -> LCD driver -> LCD.
>Maybe a clock chip in there somewhere to set how often to check the
>impedance on the probes. I just don't know where to begin to choose
Nah, just do a timing loop.
>components. I also don't know what effect adding 5' of wire between the
>probes and the controller micro will have, since a lot of them output an
>impedance relatively equal to the temp or humidity. How do I figure out how
Well, resistance. You'd calibrate it to account for the resistance in
>to offset the load difference caused by the wire? What kind of controller
>chips would I use? I've been in software since I got out of high school, so
>my EE skills are more than what you would call rusty.
PIC is popular. Personally, I'd use an AVR, since I have a couple
around, and kinda know how to program them in Bascom (a Basic compiler
> And a big one, where does everyone go for parts? I've been looking at
>several places on the web, but the last time I needed parts I went to radio
>shack, and they're no help these days. All they have is phones and
I salvage nearly everything I use, if not buying new devices with the
outright intent for certain parts inside. The AVR chips I use are from
some old satellite TV pirate equipment given to me.