I built a circuit using RPR220 photo sensor to detect the surface displacement caused on a material when external force is applied. I could see the output on a CRO even when there are minute changes on the surface for little forces applied.
Now the issue is, the output of the sensor is very low (appr 0.20mA) and for a maximum surface displacement I could see the change in the output varies between .18mA till .22mA. (the changes in the voltage is also in the milivolts range).
I used a current amplifier circuit that boosted the signal upto 100mA but still the changes in the surface resulted in minute variations at the output (the output varied from 96mA to 102mA).
How can I light an LED whenever there is a change in the average current/voltage value? Is there any logic gate IC that I can use in such a way that even if the signal fluctuates 100mA the output logic is set to one and the LED lights up?
P.S. The sensor was placed at a distance of 6mm from the surface.