7-segment decoder

[Electronics4you]

Hi All

When decoding a BCD signal into 7-segment, you can use a 7-segment decoder, but they decodes different. I normally use 4511 or 7447, but they don't decode it like other I have seen. Which chip should I use to make these?




__________________________________
Electronics make you happy - every day

 

[jbeng]

According to the databook, a 4543 (Motorola or OnSemi MC14543) decoder will give you the output you're looking for. When displaying a "6", it turns on the top bar (segment "a") and on a "9", the bottom bar (segment "d") is lit. That is, assuming that you're looking for a standard seven-segment digit and not the dot-matrix character you have shown. This chip is cool because it can drive all sorts of displays, including CA or CC seven-segment LED displays or non-multiplexed LCD displays, depending on how you connect it.
Here's a link to a datasheet.
https://www.electro-tech-online.com/custompdfs/2005/08/MC14543B-DPDF.pdf
JB

 

[Nigel Goodwin]

Another obvious solution would be a micro-controller (PIC or something else), or even a simple EPROM - that would work fine as a 7 segment decoder, but requires programming just as a PIC would. One advantage of both those solutions is your PCB layout, as they both index the segments, you can layout the connections for the easiest way, rather than having to use specific pins.

 

[eblc1388]

All the following chips decode "6" and "9" with the top and the bottom segment. (ie. segment a and d)

74143, 74144, 74246, 74247, 74LS247, 74248, 74LS248, 74249, 74LS249 & 74LS447.

 

[Electrix]

Another obvious solution would be a micro-controller (PIC or something else), or even a simple EPROM - that would work fine as a 7 segment decoder, but requires programming just as a PIC would. One advantage of both those solutions is your PCB layout, as they both index the segments, you can layout the connections for the easiest way, rather than having to use specific pins.

Hi Nigel: Do u mean to say, we build up a look-up table in the PIC and according to the digit required, we fire the desired segmets ??
I think this would be a very flexible solution !

 

[Nigel Goodwin]

Hi Nigel: Do u mean to say, we build up a look-up table in the PIC and according to the digit required, we fire the desired segmets ??
I think this would be a very flexible solution !

Yes, my seven segment tutorial does exactly that, but it's hardly a clever idea of mine, it's been common practice for years and years 8) same as using an EPROM to do it as well.

In fact, in my tutorial I didn't even calculate the bit pattern, I did it experimentally after I had built it.