BCD to Seven Segment Display Decoder, I've problem with A to F

Thread Starter

Saeed Saeed

Joined Jan 2, 2015
7
thank you all for the feedback, I really appreciate all the help. what I learned from the replies that the 74LS47 is useless in my case.

I thought about something else, which is using a 4-to-16 decoder that takes 4 inputs and gives (16 outputs).
each output will go throw another demultiplexer "or any device you guys suggest" for example it has 1 input and has 7 outputs "which I'll connect directly to the 7 segment".

for example, I entered bcd "0000" the first line in the decoder will be enabled then that line will go throw the demultiplexeer "or other device" and enables certian lines that I'll connect to the 7 segment display like this. Image

To be honest I don't think the demultiplexer will help, I want a device that can help me enable some lines or not, at least enables everything then I'll use an inverter to disables the ones that I don't need.

My ideas are kinda blurry and not clear about this, so bare with me guys.

thanks.
 

WBahn

Joined Mar 31, 2012
29,976
thank you all for the feedback, I really appreciate all the help. what I learned from the replies that the 74LS47 is useless in my case.

I thought about something else, which is using a 4-to-16 decoder that takes 4 inputs and gives (16 outputs).
each output will go throw another demultiplexer "or any device you guys suggest" for example it has 1 input and has 7 outputs "which I'll connect directly to the 7 segment".

for example, I entered bcd "0000" the first line in the decoder will be enabled then that line will go throw the demultiplexeer "or other device" and enables certian lines that I'll connect to the 7 segment display like this. Image

To be honest I don't think the demultiplexer will help, I want a device that can help me enable some lines or not, at least enables everything then I'll use an inverter to disables the ones that I don't need.

My ideas are kinda blurry and not clear about this, so bare with me guys.

thanks.
Your image only deals with 0-9 and you said that you also need to support A-F.

Why not just design a Hex to 7-segment decoder? You have four inputs and seven outputs, but each output can be designed independently.
 

Thread Starter

Saeed Saeed

Joined Jan 2, 2015
7
Your image only deals with 0-9 and you said that you also need to support A-F.

Why not just design a Hex to 7-segment decoder? You have four inputs and seven outputs, but each output can be designed independently.
I used that image because I wanted to give an idea about what I'm talking about. I'll add the rest by myself. Hmmm, to be honest I don't think my professor will accept using hex to 7 segment. So what do you guys think?
 

tshuck

Joined Oct 18, 2012
3,534
thank you all for the feedback, I really appreciate all the help. what I learned from the replies that the 74LS47 is useless in my case.

I thought about something else, which is using a 4-to-16 decoder that takes 4 inputs and gives (16 outputs).
each output will go throw another demultiplexer "or any device you guys suggest" for example it has 1 input and has 7 outputs "which I'll connect directly to the 7 segment".

for example, I entered bcd "0000" the first line in the decoder will be enabled then that line will go throw the demultiplexeer "or other device" and enables certian lines that I'll connect to the 7 segment display like this. Image

To be honest I don't think the demultiplexer will help, I want a device that can help me enable some lines or not, at least enables everything then I'll use an inverter to disables the ones that I don't need.

My ideas are kinda blurry and not clear about this, so bare with me guys.

thanks.
You did not fill it in, nor respond to my asking you to do it, so I have to ask, do you understand the image you posted?

You can describe the logic for an output and minimize the output. Look at the output column for segment A, it is like you've seen with for inputs and one output, use a K-map or Boolean algebra to minimize it - you now have segment A decoded.

Do the same for the other output columns, not forgetting the one for the decimal point (the image you linked doesn't account for it), and you are done.
 

WBahn

Joined Mar 31, 2012
29,976
So your approach would involve 16 four-input AND gates (with ten transistors in each one, assuming CMOS), 32 inverters (with two transistors each), and 80 diodes. So that's 224 transistors and 80 diodes which will give you about four gate delays of propagation delay and be non-cascadable due to the diode drops. And that's not to mention the fact that the outputs will be of the wrong polarity to drive the same type of display, namely a common anode display, that the 74x47 is designed to drive.

Actually, you've just pretty convincingly demonstrated how much of the learning process IS absent when someone just does it in software since the method you propose is way too wasteful and inefficient and is not cascadable. Perhaps if you had paid attention when you did this stuff in college, instead of just telling yourself it was nothing but a waste of your time, you would have known that.
Doing a very basic direct implementation of a hex to 7seg decoder would require 16 4-input NAND gates (8 transistors each) and 16 3-input NAND gates (6 transistors each) for a total of 224 transistors, but no diodes, only two gate delays, and it is cascadable. But with just some very simple optimization that can be reduced to 164 transistors.
 

WBahn

Joined Mar 31, 2012
29,976
I used that image because I wanted to give an idea about what I'm talking about. I'll add the rest by myself. Hmmm, to be honest I don't think my professor will accept using hex to 7 segment. So what do you guys think?
We have no way of knowing what is fair game and what is not. If this assignment is related to being able to do basic logic design, which seems likely, then I would be very surprised if you can use anything other than basic logic.
 

Thread Starter

Saeed Saeed

Joined Jan 2, 2015
7
You did not fill it in, nor respond to my asking you to do it, so I have to ask, do you understand the image you posted?

You can describe the logic for an output and minimize the output. Look at the output column for segment A, it is like you've seen with for inputs and one output, use a K-map or Boolean algebra to minimize it - you now have segment A decoded.

Do the same for the other output columns, not forgetting the one for the decimal point (the image you linked doesn't account for it), and you are done.
- ok, the image shows how to display each number, for example 0000 all of A,B,C,D,E,F = on , while g is only on
- and so on for the rest numbers: image .

We have no way of knowing what is fair game and what is not. If this assignment is related to being able to do basic logic design, which seems likely, then I would be very surprised if you can use anything other than basic logic.
ok, can you give the IC code for is "example 7447". consider that i'm using multisim so if there is a video or a page that illustrates how to connect each of the components will be really helpful.
 

tshuck

Joined Oct 18, 2012
3,534
- ok, the image shows how to display each number, for example 0000 all of A,B,C,D,E,F = on , while g is only on
- and so on for the rest numbers: image .


ok, can you give the IC code for is "example 7447". consider that i'm using multisim so if there is a video or a page that illustrates how to connect each of the components will be really helpful.
If you won't put any effort into this, neither will we.
 

MrCarlos

Joined Jan 2, 2010
400
Hello Saeed Saeed

There is much information in the network about converters from Natural Binary to HEX.
I say -converters from Natural Binary to HEX.- Because You have 4 BIT's Binary Input and need a decoder 0-9 and including the letters A through F.
So the figures on the display would be from 0 through F, which is a HEX numbers.
Simply inquiry to Google: Binary To HEX Converter*
If you want Videos, take a Click on Videos.
If you want to image, Give Click on image.
* Or Binary To HEX Decode

Because you say in your original message:
I know that 74LS47N to 7 segment shows the BCD 0 to 9. I don't know how to show the other.
I'm not experenced with any other stuff other than logic gatese, multiplexers, decoders.
I recommend you use the Boole-Deusto Software which you can also find on Google.
Right there you can find videos of how to use this software.
You can develop that decoder using multiplexers, Since you mention that you know.

Now:
Your design that I look at your original message has some things to improve.
You can compare with which I am enclosing, (Binary To BCD & A Th F Decoder 1.pdf) only that it was developed in the ISIS Proteus simulator.
One of the things to improve are the ones you have in the switches.
When these switches are open, the inputs of 7447 have an undefined level, so the outputs towards segments, also have an undefined level too.
Also, each segment in the display must have a current limiting resistor.

With respect to the statement in your original message:
Design and implement a BCD to Seven Segment Display Decoder. Your decoder should have 5 inputs (4 for the binary number and 1 for the decimal point). It should have 8 outputs (7 segment and 1 for the decimal point). It should display from 0 until F (no do not care conditions).
The black box in the document attached (BCD Binary To Th F & A Decoder 1.pdf) named Binary To HEX decoder.
It is more like mentioned in that statement.

Because you showed in your design developed with Multisim, the use a Common Anode Display, the truth table you present has the logic levels, for the segments, contrary.
So you must change ones by zeros and vice versa. As in figure I am attaching you (Binary To BCD & A Th F Decoder TrueTable.PNG)

I tried to make the decoder with Boole-Deusto but I no longer have the patience as before. It almost works but some wire plugged it wrongly. hopefully you can fix it.
(Binary BCD To Th F & A Decoder 2.pdf).

You have an Intent with the software Boole-Deusto is not so difficult.
if you think it takes many gates analyzes the figure: 74LS47 Gate Level Shematic.PNG.
It is the IC 74LS47 watched own level logic gates

Note: There are not any IC that decode Binary to HEX.
 

Attachments

Thread Starter

Saeed Saeed

Joined Jan 2, 2015
7
Hello Saeed Saeed

There is much information in the network about converters from Natural Binary to HEX.
I say -converters from Natural Binary to HEX.- Because You have 4 BIT's Binary Input and need a decoder 0-9 and including the letters A through F.
So the figures on the display would be from 0 through F, which is a HEX numbers.
Simply inquiry to Google: Binary To HEX Converter*
If you want Videos, take a Click on Videos.
If you want to image, Give Click on image.
* Or Binary To HEX Decode

Because you say in your original message:
I know that 74LS47N to 7 segment shows the BCD 0 to 9. I don't know how to show the other.
I'm not experenced with any other stuff other than logic gatese, multiplexers, decoders.
I recommend you use the Boole-Deusto Software which you can also find on Google.
Right there you can find videos of how to use this software.
You can develop that decoder using multiplexers, Since you mention that you know.

Now:
Your design that I look at your original message has some things to improve.
You can compare with which I am enclosing, (Binary To BCD & A Th F Decoder 1.pdf) only that it was developed in the ISIS Proteus simulator.
One of the things to improve are the ones you have in the switches.
When these switches are open, the inputs of 7447 have an undefined level, so the outputs towards segments, also have an undefined level too.
Also, each segment in the display must have a current limiting resistor.

With respect to the statement in your original message:
Design and implement a BCD to Seven Segment Display Decoder. Your decoder should have 5 inputs (4 for the binary number and 1 for the decimal point). It should have 8 outputs (7 segment and 1 for the decimal point). It should display from 0 until F (no do not care conditions).
The black box in the document attached (BCD Binary To Th F & A Decoder 1.pdf) named Binary To HEX decoder.
It is more like mentioned in that statement.

Because you showed in your design developed with Multisim, the use a Common Anode Display, the truth table you present has the logic levels, for the segments, contrary.
So you must change ones by zeros and vice versa. As in figure I am attaching you (Binary To BCD & A Th F Decoder TrueTable.PNG)

I tried to make the decoder with Boole-Deusto but I no longer have the patience as before. It almost works but some wire plugged it wrongly. hopefully you can fix it.
(Binary BCD To Th F & A Decoder 2.pdf).

You have an Intent with the software Boole-Deusto is not so difficult.
if you think it takes many gates analyzes the figure: 74LS47 Gate Level Shematic.PNG.
It is the IC 74LS47 watched own level logic gates

Note: There are not any IC that decode Binary to HEX.
That's a big help. ok, i'll start by this: binary-to-bcd-a-th-f-decoder-truetable-png

but I'm confused a little bit, should I do k-map for each 0,1,2,3,4...F then add all the designs together? or can I use a decoder or a multiplexer?

If it's possible to do it with decoders, i just need to know how to do 1 of them, and I'll do the rest. "I mean 1 7 segment display outcome like 5 "
 

Thread Starter

Saeed Saeed

Joined Jan 2, 2015
7
hello, I had an idea about the project.

using 7 Muxs for each segment, and the BCD are the control lines, and the rest are the column in the truth table for each segment.

example for the segment a only: Image
the truth table used: image

i'll definitely give feedback after finishing the project to help the future students xD.

Thanks for everyone who help me in this thread, you guys are awesome.
 

MrCarlos

Joined Jan 2, 2010
400
Hello Saeed Saeed

You ask:
(Should I do k-map for each 0,1,2,3,4 ... F)
Well, if you want you can.
But. . . For what ??
Including those you can see from the results that gives the Boole-Deusto.

You have a try with this software, download it from the web and install it on your PC.
See the videos, on the WEB, regarding the use of this software.
 

WBahn

Joined Mar 31, 2012
29,976
Hello Saeed Saeed

You ask:
(Should I do k-map for each 0,1,2,3,4 ... F)
Well, if you want you can.
But. . . For what ??
Including those you can see from the results that gives the Boole-Deusto.

You have a try with this software, download it from the web and install it on your PC.
See the videos, on the WEB, regarding the use of this software.
For what? I'm making a guess here, but this seems like an assignment where the intent isn't to get a hex to 7-seg decoder, but to develop and practice digital design skills at some fundamental level instead of having some software package do all your thinking for you.
 

tshuck

Joined Oct 18, 2012
3,534
Hello Saeed Saeed

You ask:
(Should I do k-map for each 0,1,2,3,4 ... F)
Well, if you want you can.
But. . . For what ??
Including those you can see from the results that gives the Boole-Deusto.

You have a try with this software, download it from the web and install it on your PC.
See the videos, on the WEB, regarding the use of this software.
It is in no way required to find some software to do it for you.

The point of this exercise is for the student to learn to do some design work on their own, not what software is available.
 

WBahn

Joined Mar 31, 2012
29,976
no, I just want to know the name of the hex to 7 segment, i'll do the rest of work.
How will that help since you've already said that your instructor won't let you use one. BTW, the ID for the hex to 7-seg IC was given earlier in this thread: MC14495. If your thought is to steal their logic diagram and simply copy it, then be forewarned that there are other functions supported by that chip that will be mixed in with the logic and that your instructor is likely aware of this and will be looking for tell tales of students going this route.

That's a big help. ok, i'll start by this: binary-to-bcd-a-th-f-decoder-truetable-png
Finally! That's what we've been trying to get you to do since Post #3!

but I'm confused a little bit, should I do k-map for each 0,1,2,3,4...F then add all the designs together?
Answered in Post #22. Each of your outputs is a different and independent problem. So you do a K-map for each segment and each K-map has four inputs.

[/QUOTE]
or can I use a decoder or a multiplexer?
If it's possible to do it with decoders, i just need to know how to do 1 of them, and I'll do the rest. "I mean 1 7 segment display outcome like 5 "[/QUOTE]

Yes it's possible to do it with decoders, though multiplexers are a more natural way to implement truth tables. But this is also inefficient use of logic resources. It really comes down to the question of what the constraints and expectations are for this assignment -- what is and what is not fair game for you to use?
 

tshuck

Joined Oct 18, 2012
3,534
hello, I had an idea about the project.

using 7 Muxs for each segment, and the BCD are the control lines, and the rest are the column in the truth table for each segment.

example for the segment a only: Image
the truth table used: image

i'll definitely give feedback after finishing the project to help the future students xD.

Thanks for everyone who help me in this thread, you guys are awesome.
While, yes, this would work, much of engineering is about efficiency and minimizing cost/board real estate/power, etc. This multiplexer approach is not the minimal logic, and would be a huge waste of resources, were it implemented as such.

Try writing out the truth table for a single output, try segment A. You should have four inputs and one output in this shortened version of the truth table.

Then, once you've done that, minimize the logic using K-maps, Boolean algebra, Quine-McCluskey, or whatever other methods you may have been taught.

Then, do the same for the remaining segments & decimal point.

Edit: WBahn beat me to it.
 

MrCarlos

Joined Jan 2, 2010
400
Hello Wbahn & tshuck:
Because as soon as the OP saw my verbiage (#30) opened his eyes of the mind and presented his idea with MUX. ( #32).
But it would have been better to follow the path of developing His design with a decoder done with logic gates.
anyway, what I do is with the intention of helping

Hello Saeed Saeed:
I recommend you to be ordered.
Otherwise you will Have a design in your multisim, very, very large.
Take a look at the attachment.
 

Attachments

tshuck

Joined Oct 18, 2012
3,534
Hello Wbahn & tshuck:
Because as soon as the OP saw my verbiage (#30) opened his eyes of the mind and presented his idea with MUX. ( #32).
But it would have been better to follow the path of developing His design with a decoder done with logic gates.
anyway, what I do is with the intention of helping

Hello Saeed Saeed:
I recommend you to be ordered.
Otherwise you will Have a design in your multisim, very, very large.
Take a look at the attachment.
Do not presume that your one post was what "opened his eyes of the mind".

He has seen this all before, he has heard it and watched it done in class.

Again, the multiplexer approach is an inefficient approach and will likely result in points lost.
 

hp1729

Joined Nov 23, 2015
2,304
Write a state table that has a number in binary as an input and 8 outputs - one for each LED in the seven segment display. Forget about the 74LS47.


X3|X2|X1|X0 | A|B|C|D|E|F|G|decimal point
0|0|0|0 | 1|1|1|1|1|1|0|0

Where X is the 4-bit input and A-G are the corresponding segments, and a segment in illuminated by a logic 1.
Tesla MHB4311 is a hexadecimal to 7-segment decoder / driver with a latch. Much like a CD4511 in pinout as I recall. I got mine from a friend in an Eastern Block country but if you can find a local Tesla distributor you should be able to get them. Price was comparable to a 4511.
 
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