555 timer and 7 segment display

Thread Starter

beratsahinf

Joined May 23, 2023
5
Hello, im trying to do circuit design that can show the letters of my name and surname on this display at 1 second intervals using a single 7 segment display. I have to use only 555 timer and some logic gates with 7 segment display. I did this circuit for 7 segment display but i dont know how can i use 555 ic timer logic.png
 

WBahn

Joined Mar 31, 2012
29,979

WBahn

Joined Mar 31, 2012
29,979
Based on what?

It either works or it doesn't -- what's with the "I think" part. That implies that you aren't sure that it works, only that you believe that it should work.

Did you do a simulation with all 16 possible input codes and verify that the display shows the correct output?

If so, then it works. If not, then it doesn't.

You are going to have a hard time finding anyone willing to work through your rat's nest maze of wires to verify that it works (or doesn't).

If you were to dramatically clean up your wiring, it would be pretty easy to verify the design.

But let's assume that it works. Where does that leave you? If you want to display characters so that you can display your name, you will need to add a LOT more logic. How much more depends on how many distinct characters you need/want to display. Also, there is no way to display some characters, such as an "M" or a "W", on a 7-segment display in a way that most people would recognize it. So you have to make compromises and use unique patterns that you just "declare" are certain letters.

This is not something that I would recommend making a discrete logic circuit for. It is, however, a good exercise for getting started with using a ROM of some kind.
 

boostbuck

Joined Oct 5, 2017
501
I understand that you have tested it by setting the four inputs to a range of values. So to progress this project you will need to create a circuit to set the four inputs for you in the sequence that generates your desired output - a counter or other sequencer that is incrementing on a clock input.

If you have organised your seven-segment decode logic to present the letters of your desired output in numerically ascending order, it will be quite simple to use a counter, otherwise you will need additional circuitry to derive the sequence you want.
 

MrChips

Joined Oct 2, 2009
30,720
This is your assignment.

Begin by drawing the 7-segment display that will represent each letter in your name.

The circuit design will come later.
 

MateoEV

Joined May 26, 2023
17
I don't know if this thread is still open, but in order to design the circuit you described you should start by generating a MOD11 binary code counter to generate the input sequence for the logic circuit (hence the use of a 555 timer to provide the digital clock signal). Also, the circuit schematics you shared is not at all helpfull nor does it share any relation to your problem.

The circuit you provided seems to work only as a binary decoder for seven-segment displays. If you are to design the circuit you described you'll have to change all the logic through Karnaugh maps or boolean algebra.
 

WBahn

Joined Mar 31, 2012
29,979
I don't know if this thread is still open, but in order to design the circuit you described you should start by generating a MOD11 binary code counter to generate the input sequence for the logic circuit (hence the use of a 555 timer to provide the digital clock signal). Also, the circuit schematics you shared is not at all helpfull nor does it share any relation to your problem.

The circuit you provided seems to work only as a binary decoder for seven-segment displays. If you are to design the circuit you described you'll have to change all the logic through Karnaugh maps or boolean algebra.
I think you meant MOD12 -- I suspect you overlooked the required space between first and last name. Also, there should probably be a space between the names when it cycles back (so MOD13, in his case), but the problem description either overlooks that, or perhaps the circuit isn't supposed to cycle continuously.

While starting off with a modulo counter that is the same length as the length of the character sequence is a nice high-level decomposition, you then have to decode the binary output and produce the seven-segment signals. This has a lot of merits to it, but it results in a lot of extraneous gate logic.

Another approach, which is less flexible but results in considerably fewer gates, is to have the states be the necessary encodings of the characters. If no characters where used twice, this would require one FF per display segment. Since 'a' is used twice, an additional FF can be used to indicate whether it is the first 'a' or the second. Similarly, it can be used to indicate first space or second. For his name, that eighth FF could very nicely serve as indicating first name or last name, which makes turning on the red and blue LEDs trivial.
 
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