'LED display without current limit resistors ?'
Happy New Year PICLISTERs
I am interfacing a PIC 16C84 to a multiplexed Common Anode 3 digit 7
segment LED display.
Power for the circuit is 2 'AA' battery cells (nominal 3V).
Each LED segment is rated for a maximum forward voltage of 2.8V.
QUESTION: Do I really need current limiting resistors ?
The individual segments are pulled down by the PIC port B outputs,
which introduce some voltage drop.
Each common anode is driven by a 2n3906 transistor. Its voltage drop
will vary around 0.2 volts depending on how many segments are turned
on. This will result in some variation in intensity, but I think I
can compensate for this by varying the mux duty cycle depending on the
number of segments turned on.
QUESTION: Has anybody tried this ? Anything I am missing here ?
I am new.
I mailed a letter to: mitvma.mit.edu titled pic damage, watchdog... piclist
Did you receive it?
If yes/no, let me know. I will act accordingly.
More... (looser matching)
- Last day of these posts
- In 1996
, 1997 only
- New search...