since all the leds are connected, how are adjacent leds off/on?
2007-09-10 17:39:41 · 2 answers · asked by J R 1 in Science & Mathematics ➔ Engineering
There are 'row' and 'column' common connections for the LEDS. By scaning across the columns and energizing only the row LED's that are to be lit, the eye 'sees' only the ones that are lit in the matrix if the scan rate is greater than about 1 full scan every 40 mS. or so. Typical scan rates are about 100 Hz and up. When used this way it is also common to overdirve the LED by several times (instead of 10 mA DC, about 30 mA or more is driven through the LED). This causes it to emit more brightly and compensates for the 'dimming' effect of only being on some small percentage of the time.
HTH
Doug
2007-09-10 18:54:39 · answer #1 · answered by doug_donaghue 7 · 2⤊ 0⤋
use an IC with gates
2007-09-11 01:14:28 · answer #2 · answered by MazterHukom 1 · 0⤊ 1⤋