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Topic: adc interfacing (Read 426 times) previous topic - next topic

nayna_15

hi frnds :)  !!!!!!!
I have a question on adc. I have 11 bit adc interfaced with PIC. the ADc i/p varies between 1v - 5v
For 11 bit adc I have corresponding voltage values in hex chart .
My basic question is that if some hysteresys occur between 2-3 values what should be the standard coding for adjusting that readings?
for ex. if  I have load-cell input of 100 kg. but my adc reads it either 98.5 or 100.5  :o
how will I get the correct 100 ?  :-/

Gravitech

Try to throw away the last 2-3 bits and see if that help. Also, low pass filter at the input of A/D might help as well  :)

mem

There is a tutorial on smoothing analog data here: http://www.arduino.cc/en/Tutorial/Smoothing

nayna_15

Hi!
Hope the link will help me in progressing further.
let me give u the detail idea of my adc input.
I get an adc i/p  voltage frm 0-5V across the register.
The i/p is rectified with the help of 10uf cap.I want to glow led when my analog i/p is 160 - 170 - 190
But my led starts blinking frm 154 - 162Vac (that to changes time by time!!)for fist i/p, since the adc is not getting a steady value.  :-?
My led should be steady (not blinking)! I tried with different hex count for adc i/p to get a steady led on.
Pls help!!!!!!!

mem

Software smoothing should help and you could also try a bigger capacitor.

You could also add some hysteresus  in your software by setting the value to turn the lamp off lower then the value to turn it on.  In your case you may want to try a turnoff value 10 or 20 less then the turn on value

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