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Vref of ADC 0804


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dtyh

Tue Jul 07 2009, 09:32PM

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Hi, i'm using ADC 0804 to interface with temperature sensor and AT80S51. I need to set the Vref of ADC to 0.512V for reading the value of sensor. I used a voltage divider circuit and adjust the potential meter to set voltage on pin 9 (Vref/2) to 0.256V but each time i on back the circuit, the voltage varies a bit and hard to re-adjust the potential meter. Is the way to set the Vref correct or is thee any other way to set Vref of 0.512V?

gopi

Wed Jul 08 2009, 12:13AM

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Connect a 10k variable resistor to pin9 and the other ends of variable resistor to +5V and GND.

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Ajay Bhargav

Wed Jul 08 2009, 05:40AM

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why dont you use opamp and amplify the i/p voltage? that will solve your problem and you can have a better measurable range.

if you still want to go with that potentiometer thing like gopi said, use a pot with more turns. (blue color box like potentiometer)

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