Actually, I had a little difficulty following the intent of the illustrated
circuit ;) It wasn't immediately clear (to me) if the batteries
represented the incoming signal, or were an attempt to bias the incoming signal
to the correct range. Given a sine wave input, my first thought would have be
to capacitively couple the incoming signal to the center of a resistor divider
biased around the midpoint of the ADC's input range.
--- In l..., "jithu_ag18" wrote: >
> hi I am currently doing my project. Iam handling the mcb2300 board.I am
entirely new for the ARM.
>
> Can any one tell me how to handle the negative voltages given to the input of
the ADC.Because the ADC range which I am using is 0 to 3.3V.
>
> Actually I want to give the sine wave as an input to the ADC and read the
digital values....
>
> Also please tell me how to see the digital values from the board.
>
> Thanks in Advance.....
>
As shown on Leon's schematic, the idea is to lift the sine wave up by
5V.
There is another way with a simple op amp. Read Chapter 4 of "Op Amps For
Everyone" and calculate the 4 resistors required for the circuit.
The book is a free TI download, Google for it.
With the 4 resistors, you form a little analog calculator that solves the
standard linear equation: y = mx + b. Let's say you have a 10V bipolar
signal; it swings through -5..0..+5. You need to rescale that 10V swing to 3.3V
so 'm' (the gain) needs to be 3.3/10 (thus a gain of 0.33). That will
give you a signal that swings through -1.65V..0..+1.65V. Now all you need to do
is lift the signal up by 1.65V so 'b' = 1.65.
Find the proper form in the case studies of Chapter 4 such that you can solve y
= 0.33x + 1.65
The TI TLV247x op amp will work on 3.3V and gets very close to the rails for
input and output. If you want to be absolutely certain that the op amp
isn't saturating, change the gain such that the output voltage swings from
0.1V..3.2V. That keeps you away from the corners of the transfer function.
Richard
Reply by Donald H●January 7, 20112011-01-07
--- In l..., "jithu_ag18" wrote: >
> hi I am currently doing my project. Iam handling the mcb2300 board.I am
entirely new for the ARM.
>
> Can any one tell me how to handle the negative voltages given to the input of
the ADC.Because the ADC range which I am using is 0 to 3.3V.
>
> Actually I want to give the sine wave as an input to the ADC and read the
digital values....
>
> Also please tell me how to see the digital values from the board.
>
> Thanks in Advance.....
>
There is NO ADC that can measure any voltage below ground.
Please read up and any ADC let alone the ADC in the LPC2378.
After you burn out a few processors, then you will understand that you can not
does that.
Google is your friend, help us help you be understanding what it is you want to
do first.
good luck, you're going to need it.
Also, ask your professor.
don
Reply by Leon Heller●January 7, 20112011-01-07
On 07/01/2011 09:36, jithendranath swamy wrote: > I want to give the sine wave as an input to the ADC
and read the digital
> values which is AC not DC.
That little circuit converts a bipolar signal to unipolar. I thought
that was what you wanted!
You'll have to write the software yourself. You should find some
examples of how to use the ADC in the Files section.
Leon
--
Leon Heller
G1HSM
Reply by jithendranath swamy●January 7, 20112011-01-07
I want to give the sine wave as an input to the ADC and read the digital values
which is AC not DC.
keep smiling....
J i t h u . . .
Reply by Leon●January 7, 20112011-01-07
--- In l..., "jithu_ag18" wrote: >
> hi I am currently doing my project. Iam handling the mcb2300 board.I am
entirely new for the ARM.
>
> Can any one tell me how to handle the negative voltages given to the input of
the ADC.Because the ADC range which I am using is 0 to 3.3V.
>
> Actually I want to give the sine wave as an input to the ADC and read the
digital values....
>
> Also please tell me how to see the digital values from the board.
>
> Thanks in Advance.....
>
