Help Me About "bcd To 7segment"

[phu hung]

I have a project : decoding BCD to 7 segment Led without using 74LS47 or IC the same 7447.
I don't know how to do ! Do you have any idea or how to solve this project, please help me !
THANK YOU VERY MUCH !!

 

[blueroomelectronics]

How about a CD4511.

 

[Brevor]

Or a bunch of diodes.

 

[RODALCO]

Make up a truth table with the BCD codes for the numbers 0 to 9, then make a diode array to make it work.

 

[Pommie]

I know how you go from 16 inputs to 4 binary outputs (ie encoder) with diodes. How do you go from BCD to 7 segment?

Mike.

 

[boxer4]

Start with something easier:
Can you decode BCD (4-input binary) to 1-of-10 (such as what a 7442 does)?

Then starting with that, follow the diode method... if output 1 of the 1-hot is on, then use two diodes to light up segments b and c, (depending on your labelling of segments).. Then if output 2 is on, then through 5 new diodes light a,b,d,e,g. Go so on and so forth and that's your really diode intensive method of doing BCD-to-7 segment.

The correct way is to actually draw out 7 truth tables and simplify from there. There's a lot of possible shared terms so you can simplify logic a lot that way.

This smells like a homework assignment if you're not allowed to use 4511, MC14495, 7448, etc...
Unfortunately I don't feel like hacking out the logic and I don't have any of my SSI/MSI IC books that have the actual logic gates in it anymore...

Else it's fairly straightforward to hack up the 7 truth tables. You have one for each segment a through g. For instance, the center "hyphen" segment, usually labelled "g" is only on when 2, 3, 4, 5, 6, 8, or 9 is displayed. So, you hack out the truth table for that. The Product for the "8" term is a3!a2!a1!a0 and you 'or' it with the expanded version representation for the other numbers 2,3,4,5,6,and 9.

This when simplified will look a lot better than the first solution, but really it's the same thing. The 7442 decoder is doing all your ANDing together, and the diodes do the OR, thus sum of products.

(note: I likely am glossing over the DeMorganing as IIRC 7442 is active low, but it's not my homework )

(and if you have to wander out on the roads, go to https://www.datasheets.org.uk/pdf/7447-datasheet/7447-datasheet.html and hit "data sheet". Then go to the Fairchild Semiconductor datasheet for this device. On page 5 is the solution.)

(edit #2 I don't think it's possible with just diodes straight from binary input, only from the full decoder. You'll need some way of generating inversions.)

 

[Super_voip]

or use an old fashion EPROM

 

[Gayan Soyza]

Another chip I'm using is MC14511.

 

[aljamri]

or use PIC microcontroller.

 

[Papabravo]

I think this question was adequately answered in the duplicate thread.
https://www.electro-tech-online.com/threads/the-circuit-like-7447.32366/

Is it the case that you don't understand the answers we have given you?

 

[Pommie]

I don't think my question was answered.

Mike.

 

[Brevor]

I know how you go from 16 inputs to 4 binary outputs (ie encoder) with diodes. How do you go from BCD to 7 segment?

Exactly the same way just more outputs than inputs.

 

[Papabravo]

I don't think my question was answered.

Mike.

Yes, but you weren't the OP, and as you well know the answer is you can't use diodes to go from BCD to 7-segment.

 

[jelek]

use matrix of diode