Electrical – LDR issue interfacing with ADC



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I want to read the voltage values of LDR (0-5V)but my desire range is less ( 1-3V) through ADC of 10-bit,but i am getting Clipped values , what can be the issue.. ??

Best Answer

You have a 1 to 3 volt signal, and are amplifying it by 20. That would result in a 20 to 60 volt signal if the amplifier were capable of that. It should be no surprise that whatever A/D this signal is being presented to is clipping.

The simplest answer is to reduce the gain so that the maximum signal of interest is just below the top end of the A/D range. If the A/D range is 0-3 volts, then you don't need any amplification at all.

A 1-3 V signal into a 0-3 V A/D will use ⅔ of the A/D range. For a 10 bit A/D, that leaves you with a resolution of 682. If that's not good enough, use a 12 bit A/D. That would give you a resolution of 2730.