Discrete Binary to 7 Segment Display - Page 1
Forum section: electronics / projects

author: Mysion
author_rank: Regular Contributor
timestamp: January 10, 2016, 02:51:09 am
content: Recently I build a little circuit that takes a binary number and converts it to a human readable form.Here's a little build log.This is version 1. It did not work for two reasons. one is that there were a tone of bad connections and dead fets. The fets were an eBay special so all bets are off. Second the original schematic was bad. Why was it bad you ask? I made last minute changes to it so it would work with a common anode display and mucked it up. Really should have double checked it.Moving on to version 2I finally figured out hierarchy in dip trace and that was a huge help in keeping it neat. Also helps prevent errors witch is nice. V1 was a MESS. All the Nand gates use Mosfets and the Or gates use diodes.For the PCB layout I gave in to the auto router and with a lot of encouraging I think it did a good job. Manged to get the board to 5 square inches in size.Final assembly took a while. I used solder paste and a hot air gun. Simple enough method with good results. I did the though hole parts last. Time to power it up annnd it doesn't work. My biggest fear was that there could be an issue with the core design. However I noticed that the decimal point would light up, a pin I never connected. So I went back and checked and sure enough I had the pad reversed. A few wire later and it works!If you want more pictures I have them in an imgur album. These three take up enough room.http://imgur.com/a/pfantThere's also a hack IO page witch includes git hub links to the design files.https://hackaday.io/project/9125-discrete-binary-to-7-segment-display

author: ChristofferB
author_rank: Frequent Contributor
timestamp: January 10, 2016, 03:07:17 am
content: This is really cool! Love your dead-bug/manhattan prototype, even if it was buggy!Nice PCB too.--Christoffer

author: Falcon69
author_rank: Super Contributor
timestamp: January 10, 2016, 03:11:35 am
content: very nice. good job

author: matseng
author_rank: Frequent Contributor
timestamp: January 10, 2016, 03:11:54 am
content: Yes, really nice. I have a thing for logic built out of discrete parts....

author: Mysion
author_rank: Regular Contributor
timestamp: January 10, 2016, 04:07:48 am
content: To ChristofferBI'm still a fan of the Manhattan style but now I under stand why mainly radios use it. Radios tend to be more modular and there aren't crazy connections flying all over the place. If I did the Manhattan style again I would be more careful about separating gates.To Falcon69Thanks!To MatsengYou and me must think a like!Older discrete electronics can be so fascinating.

author: matseng
author_rank: Frequent Contributor
timestamp: January 10, 2016, 10:06:16 am
content: Does it support full hex 0..F or just 0..9?

author: German_EE
author_rank: Super Contributor
timestamp: January 10, 2016, 11:02:40 am
content: Nice work, I have seen those square pad Manhattan pads a few times and they look like a neat solution, being cheap I punch my own using a Harbor Freight tool I purchased years ago and some scrap PCB material.

author: miguelvp
author_rank: Super Contributor
timestamp: January 11, 2016, 12:37:15 am
content: Nice, there was a thread long ago where someone wanted to do this using transistors (72 of them) I did suggested that they reverse the logic as in turning segments off instead of on and that would require only 36 transistors.https://www.eevblog.com/forum/beginners/7-segment-display-driver-for-hexadecimal/msg422666/#msg422666Code:in abcdefg T Total0000 1111110 1 10001 0110000 5 60010 1101101 2 80011 1111001 2 100100 0110011 3 130101 1011011 2 150110 0011111 2 170111 1110000 4 211000 1111111 0 211001 1110011 2 231010 1110111 1 241011 0011111 2 261100 1001110 3 291101 0111101 2 311110 1001111 2 331111 1000111 3 36Also I did implement one with PSoC logic gates:The 4-line to 16-line decoder implementation (24 AND gates and 4 NOT gates):And the 16-line to Hex 7 segment driver ended up like this (7 NOR gates and 22 OR gates):Edit: Good job reducing it all to so few transistors without needed the 4 to 16 line decoder!

author: EEVblog
author_rank: Unknown
timestamp: January 12, 2016, 04:56:47 am
content: You etched or milled out a copper clad PCB in order to do the dead bug style? Why not just matrix board or vero board?

author: macboy
author_rank: Super Contributor
timestamp: January 12, 2016, 05:00:30 pm
content: Quote from: EEVblog on January 12, 2016, 04:56:47 amNo etching or milling, it's "Manhattan" style. Those square pads/islands are glued on to the blank PCB, then component leads and wires are soldered to the islands. The PCB forms a 100% ground plane.

author: jbix
author_rank: Newbie
timestamp: January 17, 2016, 04:37:37 am
content: Looks like fun, thanks for sharing!