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.


  1. Vinicius Rodrigues de Oliveira says:

    My project is done !!!
    2 bits multiplier/divider =)

  2. mcookieman says:

    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?

  3. SQKYbeaver says:

    All discrete logic families are acceptable, including 7400, 4000, etc.

  4. Joe says:

    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?).

  5. rsdio says:

    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.”

  6. rsdio says:

    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?

  7. bootnecklad says:

    I’ve got some great ideas in my head but if we’re limited to discrete gates then most of then I can’t build. Curse you ideas that require SRAM!!!

    • SQKYbeaver says:

      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!

    • rsdio says:

      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.

    • EngineerZ says:

      You need SRAM? What about the 7489?

  8. bootnecklad says:

    For what I need I guess I could use some glue logic and hook up multiples of them. I’ll see what I can find though.

  9. rsdio says:

    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.

  10. asiekierka says:

    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?

  11. BarsMonster says:

    Please clarify can I use only NAND gates (7400) or any 74xx/40xx chip?

    • SQKYbeaver says:

      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.

  12. SQKYbeaver says:

    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.

  13. Joe says:

    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.

  14. Alex says:

    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.

  15. SQKYbeaver says:

    unfortunately we can not supply any chips, digikey is a good source, as is your local surplus store.

  16. hmm… I think I have another project to share! ;-) I don’t know if its ok with CD4xxxx …

    • Joe says:

      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.

  17. Davide says:

    International entries are allowed? I’ve alot of ideas but i’m in italy.

  18. JP Norair says:

    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.

  19. Frank says:

    Are the prizes split between multiple winners? Or will there be one winner who gets everything?

    • SQKYbeaver says:

      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.

  20. Ross_Down_Under says:

    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:



  21. byutea says:

    here my project, Telephone Intercom From TTL
    (whether this is included in this competition category? )

  22. Anon says:

    If someone submits more than 1 entry, are they eligible to win more than 1 of the prize?

  23. Фърчуууууу says:


  24. Hammer89 says:

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

  25. Anon says:

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

  26. Anon says:

    Is there a list of all the competition entries somewhere?

  27. juni says:

    i love the prizes!

  28. Cynosure says:

    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.

  29. Lea Miron says:

    I’ve the same question as @TheAlu10000: How about a 2012-Competition?

  30. Sherron Kilver says:

    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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