Hi,

The problem here is not, "can segments be blown?"  The question is
whether or not it is possible to blow segments without destroying other
display segments.  As this is a multiplexed array, other segments (ones
which you do not want to destroy) will be reverse biased, through some
forward biased segments, once the initial segment is (presumably) burned
open.

The two manufacturers I just checked (Panasonic and Chicago Miniature)
list LED reverse breakdown voltages ranging from 3V to 5V.  This matches
well with my experience.  LEDs do not tolerate reverse breakdown well.

In Neil's case, he will probably blow the one decimal point segment he
wants to and all of the non decimal point segments in the other digits
if he applies 12V to his display.  I've suggested that, except for
potential mechanical damage which might result from the technique, he
might have success as long as he keeps his supply voltage at 3V or so.
This avoids reverse biasing any of the LED junctions to breakdown.

Dave

Bala.Chandar@AVENTIS.COM wrote:
> Neil wrote:
>
>
>>...
>>So if I selectively zap each of the OFF decimal points with
>>say 12V, can I
>>selectively destroy those dp's WITHOUT destroying any other
>>display segments?
>
>
> Neil,
>
> Yes, it can be done that way. I have done this in the past, accidentally
> though.
>
> I was testing a new 7-segment display; while the common cathode of the
> display was connected to Gnd, the +9V lead of the power supply made
> accidental contact with the anode of a segment. The "d" segment burned
> brightly for a few milliseconds and became dead.
>
> The display when off looks quite normal - no burn marks to indicate that one
> segment is destroyed. It's lying unused ever since. I can still use it as
> long as the number I need to display is limited to 1, 4 or 7!
>
> Regards,
> Bala
>
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