I would like to create a tachometer with the light sensor OPB704WZ.
I followed this schema https://tonyrobotdt081.wordpress.com/2014/04/10/report-on-the-light-sensor-opb704wz/ on a bread board (for now), and tried to measure the voltage difference on the signal pin (green on the schema).
Problem is, I don't see a clear difference between a white surface and a black one; It does change if I put the sensor closer or further away, but that's about all I can see.
Is there something else I need to add to my wiring to make the difference between high and low depending on the luminosity more obvious? I know others have been able to use this sensor for the same purpose.