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'] How can I destroy select LED segments?'
2003\08\25@041223 by Nigel Orr

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> 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?

If you destroy the segment, it is possible that it will damage other parts
of the display, though unlikely.  Most likely problem is that it may
'smoke' and leave a scorch mark somewhere visible.  IME, reverse voltage is
more likely to kill an LED without it getting so hot, that might help you!

However, why can't you just cut the DP wire on the displays where you don't
want a decimal point?  Or cut the track to the DP pin if they are already
fitted?  I think there's something you're not telling us, those
alternatives seem so obvious I suspect you've already ruled them out for
some reason :-)

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Nigel Orr, Design Engineer                 spam_OUTnigelTakeThisOuTspamaxoninstruments.co.uk
Axon Instruments Ltd., Wardes Road,Inverurie,Aberdeenshire,UK,AB51 3TT
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2003\08\25@041637 by Wouter van Ooijen

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> However, why can't you just cut the DP wire on the displays
> where you don't want a decimal point?

He already stated: multi-digit package, no access to individuel segment
wires.

Wouter van Ooijen

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2003\08\25@050320 by Bala.Chandar

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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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2003\08\25@081319 by Spehro Pefhany

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At 02:29 PM 8/25/2003 +0530, you wrote:


>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!

Did it go open or short?

How about shunting the unwanted LEDs with 1N4148s? Probably more components
than using a resistor or single-transistor inverter, but easy to tack on
the bottom of a PCB as a klingon "fix" for one or two pieces.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
.....speffKILLspamspam@spam@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

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2003\08\26@002859 by Bala.Chandar

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Spehro Pefhany wrote:

> > 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!
>
> Did it go open or short?

It failed open. My guess is that LEDs, whatever the type, when supplied with
higher current than what they can handle, fail open.

Regards,
Bala

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