16 segment display decoder

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16 segment display decoder

Postby azry » Sun Nov 14, 2010 8:48 pm

Hi, would like to ask is there a decoder ic to display alphabets on a 16 segment display?
If a 7 segment display uses the 7447 decoder ic to display numbers, then what about a 16 segment display?
Is there such ic that can output alphabet based on a 5 or 6 bit input like the 7447 decoder?

Tried googling around but to no avail. Hope any experts here can enlighten me on this.

Thank You
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Re: 16 segment display decoder

Postby ABSF » Mon Nov 15, 2010 3:06 pm

I have a microprocessor board using this type of 16-segment display. But it was in a 20-characters flouresene flat tube. AFAIK it deosn't have a decoder in it but it used the onboard uprocessor's ports to turn on and off each segment using multiplexing method. I can't find the board now. Don't know where I chat it. But I still remember the uprocessor is a 65C02 variant.

Even you can find the decoder, it would be very expansive as not many of them were being produced. Why not use a PIC with 2*8 ports or 2 pc eproms and cascade them together as a 16-bit eprom to act as a decoder. I do have 16 bits wide eprom but you must have the means to program it.

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Re: 16 segment display decoder

Postby azry » Tue Nov 16, 2010 3:47 pm

ABSF WROTE:I have a microprocessor board using this type of 16-segment display. But it was in a 20-characters flouresene flat tube. AFAIK it deosn't have a decoder in it but it used the onboard uprocessor's ports to turn on and off each segment using multiplexing method. I can't find the board now. Don't know where I chat it. But I still remember the uprocessor is a 65C02 variant.

Even you can find the decoder, it would be very expansive as not many of them were being produced. Why not use a PIC with 2*8 ports or 2 pc eproms and cascade them together as a 16-bit eprom to act as a decoder. I do have 16 bits wide eprom but you must have the means to program it.

Allen


Actually its for my project. Initial plan was to use pic as the decoder, just wondering if I can save some ports at the pic to connect other peripheral devices.

So now I have tabulate the output for each alphabet and program that into the pic correct?

Thanks Allen for that information!
Have a nice Day!
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Re: 16 segment display decoder

Postby ober » Thu Nov 18, 2010 11:14 am

Yes, we seldom see, or should I say never see decoder for 16 segment display. Might be because is too rarely used. Anyway, as ABSF said, a microcontroller with enough IO should be easily be programmed as the decoder.
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Re: 16 segment display decoder

Postby shahrul » Thu Nov 18, 2010 4:14 pm

Maybe you might use TLC5940. That's 16 Channel LED Driver using SPI.
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Re: 16 segment display decoder

Postby ober » Fri Nov 19, 2010 11:11 pm

shahrul WROTE:Maybe you might use TLC5940. That's 16 Channel LED Driver using SPI.

Shahrul, you use that chip before? Seem to be powerful chip... 16 channels of PWM?
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Re: 16 segment display decoder

Postby shahrul » Tue Nov 23, 2010 9:31 pm

ober WROTE:
shahrul WROTE:Maybe you might use TLC5940. That's 16 Channel LED Driver using SPI.

Shahrul, you use that chip before? Seem to be powerful chip... 16 channels of PWM?

I have buy this chip, still try to program. It price >RM10/unit
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Re: 16 segment display decoder

Postby yonghui » Wed Nov 24, 2010 9:09 am

hi,

i saw microchip new PIC16F1 series got segmental LCD driver.example, try seek for 16F193X . it has up to 16/ 24 segment pins for driving the LCD.
thanks&regards,
yh
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Re: 16 segment display decoder

Postby ABSF » Sat Nov 27, 2010 11:55 pm

Come to think about your problem again, using a PIC say 16F877a to decode will use up 16 port pins for the segments. And if you have 8 characters (you didn't say how many char in your display), another 8 port pins for the characters. So what's left in your 16f877a will be limited for you to use.

One way to do it is a two PIC solution. One for your main program and another sorely for decoding only. The decoder will take 8 data inputs from the main PIC.

Of course there is another way to do it and it is to use a 16 segment driver with serial inputs (I2C or SPI) like MAX6969. There was a discussion (2008) of this chip here:

http://www.electro-tech-online.com/micr ... ver-2.html

The datasheet of MAX6969 is here:

http://datasheets.maxim-ic.com/en/ds/MAX6969.pdf

And you can get the chip here in PDIP 24 pin package here:

http://search.digikey.com/scripts/DkSea ... 9ANG%2B-ND

USD 8.87 + postage is not too bad. Or you can try to write to MAXIM asking for a free sample. I did it last time and they did sent me the free sample but in SMT package :roll:

Best of lock with your project and cheers

Allen
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Re: 16 segment display decoder

Postby ober » Sun Nov 28, 2010 5:44 pm

Maybe a latch could be helpful and easier to save more IO?

Use 74HC573, very cheap latch, 8 output latch. You might need 2 of these, still consider very cheap solution.
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