HI, everyone!
I have a problem regarding my thesis. I am doing a project called LED MATRIX KEYPAD! LEDs can be used as light detectors, and my project is based on that. I have 12 LEDs connected in 3 rows x 4 columns. Ooo, LEDs must be pointed to a light source or ambient light will also work. Problem is, if I connect only one row everything is OK! I get numbers displayed from 0-3 on a 7-seg. display, if a "touch" LEDs one by one. BUT when I connect other two rows everything collapses!!! What am I missing here? I am suspecting that current leakage is ocurring when I charge LEDs reverse-biased, so my time measurements of LEDs discharging are way off, or ???