Open 7400 Logic Competition

See the 2012 Competition page for the latest news!

The Open 7400 Logic Competition brings awareness to open hardware and software, and fosters understanding of the building blocks of modern integrated circuits. What can you build with logic chips?


More prizes are being added as we find new sponsors. If you’d like to sponsor the contest, please drop us a note via the contact form.

Logos Electromechanical LLC

The Gadget factory


Entries can be posted on in our forum, on your personal blog, or even a handy how-to site like Instructables. When you’re ready, please submit a link to your project via the contact form.

Judging criteria and categories

Entries will be judged for:

  • Originality. A smart new design that inspires
  • Documentation. Schematics, theory, pictures and/or video
  • (Mis)use of 7400 logic. Show us what 7400 logic was (never) meant to do
  • Technical prowess
  • Build quality
  • Imagination and creativity


  1. Any electronic circuit can be entered, but judges will favor designs where discrete logic chips are a major component. All discrete logic families are acceptable, including 7400, 4000, etc.
  2. Original entries will score you the most points. Please don’t copy existing designs from the internet.
  3. Submit as many projects as you want, but please submit each separately.
  4. Good documentation is a must. Use a video, pictures, schematics, etc to document the project and show it in action.
  5. Project files must be released under an open source license. Closed source software or hardware is allowed, but the design of the logic portion should be fully disclosed and redistributable.
  6. We want to show off your project, and other websites will too. You agree to allow any part of your submission to be republished here and at other media outlets.
  7. All rules, categories and decisions are subject to change at any time. We’ll do our best to let you know about any changes and why they were made.
  8. Entries must be received by October 21, 2011, 6AM GMT. Winners will be announced on this webpage by November 1, 2011. See the list of winners.

Legal stuff

We want everyone to have fun, and nobody to get sued. Welcome to the legal section.

  • Void where prohibited. The competition is open to world wide participants, unless your local laws say otherwise. We aren’t lawyers, so you need to determine any restrictions on your own, before entering. If you win a prize and can’t collect it, you will need to work it out on your own.
  • Pay your own taxes. If you win a prize and taxes or import duties are due, you will need to work it out on your own.
  • No purchase necessary for entry. This isn’t a lottery.
  • Permission to use your entry. We need to post your entry on the blog. By entering the contest the entrant(s) consent to have all submitted material related to the contest used without notification. Likely uses are promoting the contest and open hardware, and advertising for competition sponsors.
  • Judging. Our judges’ decision is final.
  • Legal paranoia. Entries that violate local, Federal, or international law may  be disqualified.
  • Rules may change. If the rules do change we will publish the changes as quickly as possible.

Illustrations by Svenw1980

Rules and legal inspiration taken from the awesome 555 Contest.

*Cash prize paid by PayPal or money order. If the winner is unable to receive it, or there’s a legal problem with a cash prize, we’ll donate the money to the Electronic Frontier Foundation in the winner’s name.

Join the Conversation


  1. I have a few questions, can does the circuit have to have a 7400 or could I make something out of 4000 series ICs without any 7400s?

  2. So obviously since it doesn’t have to be 7400/4000 family devices, it can be entirely discreet transistors and not just gates? There are even arrays in DIPs that have 3 pins per device on the case. Also, I wonder if anyone will use just 7400 chips and no 74xx chips. That would be a real challenge to do on a single board. NAND gates are in theory a great atom for digital logic. You can make XOR gates out of 4 for example. Already, some people at the HaD site are talking about wirewrapping and RF modulation(PWM?).

    1. For clarification, there are many packages available that house the simple logic gates, the intent of this competition is based around the use of logic gates.

      1. It’s pretty wide open. Anyone is welcome to enter anything (local laws permitting), we’ll let the judges sort it out ;)

  3. It totally makes sense that you want to show off the project entries and need permission for republishing. However, it might help if you promised to give credit to the designer rather than expect them to grant open-ended permission to republish without any restrictions whatsoever. Perhaps there is an open license that would be appropriate?

    I can see that it might be burdensome to notify the contestant every time their design is published, so I also understand the need for permission to use without notification. However, again it would be beneficial to promise that you will always give credit even if you cannot notify.

    Typo alert: “The competition is open to word wide participants, unless your local laws say otherwise.”

    I’m sure you didn’t intend to restrict this competition to .doc file formats, so that probably should read “world wide.”

  4. One question seems to remain unanswered: Do discrete transistors count? You can certainly build some gates with a single transistor, and other gates with a simple combination of transistors. Would those count so long as their being used to implement standard boolean logic functions?

    1. If you want to use sram, go ahead, from the rules

      “Any electronic circuit can be entered, but judges will favor designs where discrete logic chips are a major component. All discrete logic families are acceptable, including 7400, 4000, etc.”

      Implementing an 256 byte sram would take a long time and a large space using nor gates.

      We want you to be able to compete!

    2. If you just need to store a single word, then a latch or array of flip-flops can be used. It would be cumbersome to do hundreds of these, but sometimes all you need is storage for one word at a time.

  5. Hey bootnecklad, if you haven’t published the thing you’ve already been building, then who would know that you’d already started? I can’t speak for the contest judges, but an unpublished project should certainly be fair game. Even if it’s published, they might accept it if it’s unique, but that’s a tougher call to make.

    1. Does that mean I have to remove the things that I publish? Ehehehe. I’ll leave it all up and enter it in anyway when I finish. If its accepted then its accepted! I’ve got nothing to lose.

  6. I cannot get real electronic components required for this kind of thing. Is it possible to enter a simulation-only project? If yes, which simulators are allowed?

    1. that is something you would have to think about, you would be basically submitting an unfinished project.

    1. from the rules “Any electronic circuit can be entered, but judges will favor designs where discrete logic chips are a major component. All discrete logic families are acceptable, including 7400, 4000, etc.”

      any logic gate type can be used.

  7. it will be up to the judges to determine what chips are worth more points. the chips you use will not be the only determining factor.

  8. Yeah, the 7400 is not the only chip allowed. I was (half) joking about someone going for the extra challenge of sticking to just one model of chip. I’m not sure if I still have them but there are 4-bit ALUs that are essentially universal logic and much more compact and practical than 7400s.

    I have never seen an ‘888, though. I just had the ‘181. The 74HC181 would be perfect for many projects I can think of if combined with a shift register and some of those even without the register. :) The 4-bit ALU is made so that you can do 32 types of operations on 4-bit words.

  9. Do you guys provide free samples of TI 74xx chips for the project? If not, do I need to source it from DigiKey or can I pick up at a local Radio Shack store? Thanks.

    1. They seem to allow all discreet logic chips. I think the point of the competition was to avoid CPUs or FPGAs or such. You’d be amazed at what you can get away with using just transistors and 74HC parts like the ’00 ’20 ’32 and so on. (‘xx means 74HCxx or 74LSxx or 74xx or other 74 parts ending with xx)

      I’m tempted to do it for some of the 2nd or 3rd prizes just for the fun but I’m busy on a testing equipment (transistor/diode/capacitor/etc.) project ATM.

  10. In April 2002 I built a “Simon” game out of pure 7400 logic. This was a class project, although the idea was really to use a CPLD. I was old-fashioned, and still am (i.e. my favorite programming language is a soldering iron :) ). I am too old to care about the prize, but I’ll see if I can find the schematic. I know I kept it somewhere.

    1. prizes will be split up, there have been more interested sponsors than first estimated.

      there will be the grand prize winner and the two runners up, there will be other winners too.

  11. So …. any objections to using some RTL (resistor transistor logic) chips. Think I still have a hand full somewhere just waiting for this competition. :lol:



  12. Can we submit a circuit design and demo through Multisim or does the demo have to be a physical circuit?

  13. I’m really surprised that people are submitting designs they made years ago. Common guys, fresh new cool designs please!!

  14. I missed this contest, but I have started working on a huge CMOS based project. Will there be another contest held soon? I would love to enter it.

  15. I have to say that for the past couple of hours i have been hooked by the impressive articles on this blog. Keep up the great work.

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