7 segment decoder from www.falstad.com

[Alexander]

Hi.
In this circuit simulator http://www.falstad.com/circuit/ there is a sample of 7 segment decoder that has less components that the decoders that I found here, and some, that i build myself. I grabbed it from there and now I'm trying to understand its logic and may be I'll build more simple decoder with more clear logic.

[admin]

Yes, this is nice and smaller than one I’ve built, but it only work for 0-9 range, while mine can show all the hexadecimal numbers 0-f. So if one only needs to show decimal numbers yours will be better, but when all the bit combinations are possible then a bit more complicated circuit needs to be used.

[Alexander]

When building the display decoder, the main question is, where to put the special symbols ? Like "blank", "minus" and others. If ABCDEF letters are at their places, then the "minus" and "blank" are at their own pins, but if not what is easier? In my circuit I put the minus at 11 position and the blank at 12. But I haven't build any complex circuit yet to test it.

[Alexander]

This is my version. I think it's really small! If everyone could make smaller I would be pleased to see it! There are just numbers 0-9. The numbers that are displayed after 9 are just the garbage and payment for simplicity.

[Alexander]

This is my version that can show hexadecimal numbers. My decoders work in "inverted" logic. Instead off turning on the needed segments it turning of the unneeded. There are less segments that had to be turned off, so we need less gates!

[admin]

This is pretty cool it uses less gates and less input pins for them, so there are going to be less transistors on the real life circuits.

[Alexander]

Yes, but it is not critical for this decoders, because it not so useful. Just for the purpose of learning.