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Topic: Analog reading fluctuating (Read 554 times) previous topic - next topic

polymorph

Did you read the link I gave? It actually gives precisely the connection you show as one of the wrong ways to connect unused sections, and tells you why.
Steve Greenfield AE7HD
Drawing Schematics: tinyurl.com/23mo9pf - tinyurl.com/o97ysyx - tinyurl.com/q7uqnvn
Multitasking: forum.arduino.cc/index.php?topic=223286.0
gammon.com.au/blink - gammon.com.au/serial - gammon.com.au/interrupts

adam1273

And back to: your Op Amp is connected incorrectly. Why are you ignoring me on that?
Im not ignoring you at all, I really appreciate all your help. Can you please explain more on how to connect it correctly? Do i have to use two power supplies? "Input Common-Mode Voltage Range Includes
Ground " from the lm324 datasheet can i use Vcc and ground to power the op amp, and connect as a buffer as showed but instead connect V+ve to ground? Thanks again alot

Paulcet

What you have put in your schematic is essentially

Quote
Joining the inputs to each other but leaving them otherwise unconnected has almost exactly the same, bad, effects.


We are not talking about dual power supplies, we are talking about the inputs!  This is how to connect it correctly:

Quote
The simplest way to provide such an input is to connect to the midpoint of two high value (~½ MΩ) resistors in series between the supply rails.

polymorph

Steve Greenfield AE7HD
Drawing Schematics: tinyurl.com/23mo9pf - tinyurl.com/o97ysyx - tinyurl.com/q7uqnvn
Multitasking: forum.arduino.cc/index.php?topic=223286.0
gammon.com.au/blink - gammon.com.au/serial - gammon.com.au/interrupts

adam1273

Thanks again everybody its working much better after following Polymorph instructions on how to connected the unused op-amps, thanks alot sorry for being such a pain in the ___, i just couldn't get my head around it. My results are much more accurate and stable now.

polymorph

Steve Greenfield AE7HD
Drawing Schematics: tinyurl.com/23mo9pf - tinyurl.com/o97ysyx - tinyurl.com/q7uqnvn
Multitasking: forum.arduino.cc/index.php?topic=223286.0
gammon.com.au/blink - gammon.com.au/serial - gammon.com.au/interrupts

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