At 02:51 PM 9/3/2003 +0100, you wrote:


>The current depends on the number of segments lit, and how bright they need
>to be.  For all segments lit, a 20mA common cathode current is only 20/7 =
>2.8mA per segment, which seems very low, especialy if the displays are
>multiplexed.

Yes, with 4 digits that would only be 700uA average per segment,
which would be acceptable used indoors, with a reasonable filter, but
only with a high-performance display- with a cheap one it would be too dim.

In the old days we needed more like 8mA/segment average, which would be
250mA+ for the display (and each cathode driver). If you want daylight
visibility, using a high-performance display and a good filter, it's still
nice to go up to 15mA/segment average, which is almost 500mA.

Best regards,

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

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