Hi, I'm working on a project that involves displaying the following words on three 7-segment -displays.

1. A S U
2. F O E
3. C S E
4. F U N


Each word should transition to the next after a one-second interval.

I made it by creating a truth table for each display and implemented it using logic gates. For instance, inputting 00 to the 3 displays results in showing "A S U," inputting 01 shows "F O E," and so on.

I showed that to my professor and he was fine with it (That's how most students did it). However, I believe there might be a more efficient, less cluttered approach. All suggestions would be incredibly valuable to me, especially since this is my first experience with electronics!


Here are my circuits, where each display has a set of characters:






And here's how the 3 displays should change every second:

 

Unless the use of discrete logic is a bounding requirement of your project, a smarter and cleverer way is to use a microcontroller and put the complexity into software. The hardware is then at it's minimum with only a microcontroller chip and your displays.

As an example: https://www.romanblack.com/led_none.htm

 

Unless the use of discrete logic is a bounding requirement of your project, a smarter and cleverer way is to use a microcontroller and put the complexity into software. The hardware is then at it's minimum with only a microcontroller chip and your displays.

As an example: https://www.romanblack.com/led_none.htm

Cannot use microcontrollers for this project, unfortunately.

 

I showed that to my professor and he was fine with it (That's how most students did it). However, I believe there might be a more efficient, less cluttered approach. All suggestions would be incredibly valuable to me, especially since this is my first experience with electronics!

A lookup table in some nonvolatile memory would require fewer devices.

Post schematics instead of wiring diagrams. We are able to discern circuit intent much easier from well drawn schematics.

Colorful wiring diagrams and schematics remind me of children playing with crayons.

 

A lookup table in some nonvolatile memory would require fewer devices.

Post schematics instead of wiring diagrams. We are able to discern circuit intent much easier from well drawn schematics.

Colorful wiring diagrams and schematics remind me of children playing with crayons.

Sorry about that!
Here's the schematics for the first display that shows the three letters: AFCF

I want to implement this same logic, but in a less cluttered way, and preferably without using memory!

 

You can use a set of four dual 4:1 multiplexers for each digit. Look at the dataheet for a 74HC153
SNx4HC153 Dual 4-Line To 1-Line Data Selectors/Multiplexers datasheet (Rev. E)
Each multiplexer will output 4 different values for 2 bits of the 7-segment display. Just as if it was a memory device. Easy peasy.

 

You can use a set of four dual 4:1 multiplexers for each digit. Look at the dataheet for a 74HC153
SNx4HC153 Dual 4-Line To 1-Line Data Selectors/Multiplexers datasheet (Rev. E)
Each multiplexer will output 4 different values for 2 bits of the 7-segment display. Just as if it was a memory device. Easy peasy.

Thanks so much for your reply!

Would it be possible to use a counter to sequentially count from 00 to 11, and then channel this count through the multiplexers, resulting in a corresponding change on the 7-segment displays? For instance, would this setup enable the display to show 'ASU' for the count '00', 'FOE' for '01', 'CSE' for '10', and 'FUN' for '11'? (Like my messy circuit above )


Sorry if it's a stupid question, as I've never interacted with circuits before.

 

Here's the schematics for the first display that shows the three letters: AFCF

We don't draw schematics that way. It makes my head spin following the wires back and forth to establish how they're connected. The preferred flow in schematics is left to right and top to bottom.

What type of switches are you using? When contacts are open, you have floating inputs and that's a no-no.

Using essentially a single current limiting resistor for all segments is a bad design practice as brightness depends on the number of segments that are turned on.

 

You can use a set of four dual 4:1 multiplexers for each digit. Look at the dataheet for a 74HC153
SNx4HC153 Dual 4-Line To 1-Line Data Selectors/Multiplexers datasheet (Rev. E)
Each multiplexer will output 4 different values for 2 bits of the 7-segment display. Just as if it was a memory device. Easy peasy.

And if I understood correctly, 4 for each digit, so 12 dual 4:1 multiplexers in total for 3 displays.

 

And if I understood correctly, 4 for each digit, so 12 dual 4:1 multiplexers in total for 3 displays.

Yep, that's what my calculations indicate. It is not pretty, but it works without that nasty 8-pin microcontroller.

 

You already have a thread on this.

https://forum.allaboutcircuits.com/threads/words-on-7-segment-displays.197618/