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How to drive a 7 seg LCD?

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david90

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7 seg LCD

how do you drive it? is it multiplex like 7seg LED?
 

Re: 7 seg LCD

in 7 seg LCD s you have to give BCD value and digit select input value to display perticular digit.

For example 7211 is 3½ Digit lcd driver you have to give BCD value to display and perticular digit select value to display

You need to have separate driver IC for 7 seg LCD. Digits are multiplexed and selected using digit sel pins
 

Re: 7 seg LCD

Basically yes - but the LCD has a much slower response than an LED so the
multiplexing frequency cannot be very high.
On the other hand a static drive is not good either because it will cause "burn-in"
of the segments.
Check this link for some useful information: **broken link removed**
 

Re: 7 seg LCD

I got a couple of old cheapo multimeter each about 3 bucks and they have a 4 digits 7seg LCD. I opened up the multimeter trying to see if I could rip out the LCD to use with my project. The LCD in the multimeter has no output wires but only a rail of soft spongy material that lay against the trace on the PCB. The spongy material is conductive i guess.

Is there a socket or some sort that I could insert the LCD into that has output wires to the LCD?
 

Re: 7 seg LCD

The spongy material is an elastomeric connector commonly known as a "zebra strip".
If you check the 3555A datasheet on this site **broken link removed**
you will see that there is a type of connector that "pinches" the glas - but I have
no idea of how to get hold of it.
The connecting pads on the glas are very sensitive to scratches so maybe your
best bet is to reuse the zebra strips and make your own PCB with the same
connector layout as in the multimeter - and preferably the PCB pads should be
gold coated.
 

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