Designing a 7-segment hex decoder

Building a combinational logic circuit to decode 8 bits and display a 3-digit decimal number on 7-segment displays is complex. In this video, I build something much simpler—a circuit that decodes 4 bits to a one-digit hexadecimal display—and even that's pretty complicated. In future videos, we'll look at much easier ways of doing this, which we'll use for our computer's output register and then as a key element of the control logic.

You don't really want to build this do you? If you do, you'll need some breadboards, 5x 74LS32s, 9x 74LS08s, 1x 74LS04, 1x common anode 7-segment display, 1x 100Ω resistor for the display, some DIP switches, LEDs, and 1k pullup resistors for the input, and hours of podcasts or something to keep you from losing your mind. :)

If you do build this, you'll _really_ appreciate the elegance of the next few videos.

[MIKAEL]

"And i realize this is a bit messy..." and then pulls out huge diagram. I'm always amazed how much work you put into these and for anyone else wanting to make the decoder, it isn't too bad, it's just a lot of and gates.

[solivictus]

Your videos are the foundation of my Minecraft storage system, thank you for the great explanation.

[wanhazim]

If only Ben Eater knows how many times I would come back to his videos for reference for my college assignments, he would probably be shocked. He is a lifesaver, a hero for me.

[WisdomVendor]

When I was in electrical engineering college several decades ago, digital design was by far my favorite class along with DD Lab.

[ericparent]

Ben, thank you so much for your videos. I believe I've already mentioned it before, but you're the one who made me realize that electronics are so much simpler than I ever thought they were, and so thanks to you I'm now loving a new hobby, and I'm already building circuits on my breadboard. Thanks again! Eric from Ottawa, Ontario

[neodonkey]

Just to point out for people saying use a karnaugh map or an mcu etc, I'm sure ben is aware of all those things, he's teaching you this as a tool. It allows him to show you how it works in the clearest way, and the difference between combinatorial and sequential logic, introduce eeproms which no doubt are used later on for microcode etc - that's what I love about this series, everything leads onto everything else, its great!

You don't want him dropping k-maps on you just yet.

[ELVTechnology]

I feel everyone saying you could do this with an off the shelf chip, or an Arduino are missing the point of this video.

This teaches HOW it works, as well as the underlying theory and fundamentals.

[DigitalBhangari]

Dude you actually went to the trouble of putting it all together just to demonstrate how it works.. respect!

[chrisguli]

Ben love your videos - this 7 segment decoder project makes me feel like a 14 year old again (mid 70s), when I lit up my first 7 segment display on a breadboard. I then bought a board at my local Radio Shack which used a 7447 and 7 segment common anode decimal (0-9) decoder...I bought the parts at Poly Paks mail order from my allowance savings. I was always fascinated by 7 segment displays on cash registers, pinball machines, etc.

[valentin]

It was a part of my course project. I had to join 3 seven-segments monitors and show counting from 0 to 255 on them. I calculated a circuit but finally implemented it in Electronic Workbench. Then I found a circuit in 555 series which I could use in cascade connecting to realize the project. It took a lot of time but it was one of the most interesting projects =)
Thank you for your videos!

[rikilshah]

Your breadboard circuits are pieces of art, Says a guy who has done unthinkable messes on breadboard. I studied all Digital circuits 10 years backs in Engineering and yet your explanation teaches something new! Good job, Ben!

[penniesshillings]

"Of course I build the thing."
Me: "You what?"

Epic. Ben, I really love your videos!

[rcollins]

@12:30 "To demenstrate that, of course I built the thing." LOL, noice

[retrohd_]

That wiring though ❤️ That must’ve took at least 5 hours and some serious patience. I can tell because I’ve wired simpler circuits, and boy do I get confused when I forget something.

[alexgochenour]

This must’ve taken a whole week to do. You have fulfilled my curiosity for me. Thanks Ben!

[kinghassy]

I'm happy he's getting rewarded for all the effort with lots of views

[TymerTopCat]

This was awesome. This really gives a person perspective when trying to drive seven segment displays using a microcontroller. Takes too many I/O pins to do this once you get more than 2 or 3 displays.

[binaryflawgic]

You reminded me of my freshman year (not so long ago). There was an exercise to find a simplified logic equation (I don't even remember how they are properly called...) of a 7-segment display. I spent so much time, writing down the truth table, then the Karnaugh map, then simplifying things...

[Hugmanrique]

The dedication you put into your videos is amazing. Thanks for your great explanation!

[synthsam]

When i studied digital electronics, we were asked to make circuits like this and two days later after it was corrected our teacher just showed us there's a IC that makes exactly that, from memories to counters the same history.