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rbt
09-08-2007, 05:28 PM
hello guys,

i am working with adc, comparator(discrete) and AVRs, i am just at trial stage and facing some fundamental problem with ADCs interface.
Basic connection representation for adc is with variable resistance. So i connect it like voltage divider and it works for single channel. But when i connect a another potentiometer at second channel (channel3)whole things got unbalance i.e. value at channel 1 also get change due to the equivalent resistance at channel1 change due second pot.
Here i am attaching drawing of my connections. drawing only consist of channel connections i had done other connection but not drawn.
http://img259.imageshack.us/img259/4413/testxc6.png
i use channel 0 and 2 , I was not good in electric network subject :wink: . I have to use this kind of connection (potentiometer) and not differential mode, so please suggest me correct connections,

a7400
09-08-2007, 06:36 PM
you can chk out this tutorial
http://www.triindia.co.in/resources/?p=64

rbt
09-08-2007, 06:49 PM
rbt

a7400
09-09-2007, 10:15 AM
i dont see how they are in parallel. if you dont take the middle terminal of the potentiometer only then they are in parallel.

parallel means being connected at two common points.
here the mid terminals are not connected to a common points.

this ckt should work. check whether you have decoupling capacitors on the AVcc and Aref pins
also make sure that the potentiometers are not too far away from the ADC pins. because a longer track for an ADC input is more susceptible to noise.

rbt
09-09-2007, 05:50 PM
sorry :oops: :oops: :oops:

my mistake, u know what i coincidently correct my error myself while drawing the above schematic. :P In actual circuit i connect the high end (1) and wiper terminal (2), as done in some audio circuit

a7400
09-10-2007, 10:14 AM
:)
cheers