Design Challenge: Hung Jury


We’re not really hung, but it is taking a while for us to decide just who get the title. While we decide, here’s a couple more entries remind you what it’s all about.

[Razvan] sent in this excellent entry. (I’m hosting it on my personal server since he didn’t have one)
The writeup could be a bit clearer, but the design is pretty sweet. It features a mega avr brain and a microchip ethernet controller with a software based USB interface. It’s a pretty intriguing design – lots of possibilities for ethernet controllable projects.

[Tom D] sent in this rolling codes garage door opener. This will step through all the garage door opener codes for garage doors made before 2003.

26 thoughts on “Design Challenge: Hung Jury

  1. I like. Would work great for places with a large number of doors, like at a firestation. would also be cool if you could build a receiver that rotated through a set number of codes

  2. Quote: “We’re not really hung”.
    Takes a brave man to admit that, Will. Admitting you have a problem is the first step. Now publish your email address and you’ll get an inbox full of herbal remedies that will fix it :-)

  3. jesus christ, shouldn’t you have to submit a coherent writeup to get nominated? i’m sorry, but that first write up is pathetic.

    where in the writeup does he describe the “only proper way” to get RS-232 – ttl? now that would have been a great entry — a do-it-all level shifter, from 3-5v ttl/cmos to RS232 (with or without inversion) and back.

  4. “(I’m hosting it on my personal server since he didn’t have one)”

    Instead of hosting, I vote that you give that man a copy of wordpad.exe. Titles and maybe underlining a thing or two would do wonders for that project. :)

  5. Until now projects are rather boring and useless. Who needs such an opener? Modern doors can’t be opened anyway and the idea is still existent on the web. And the ethernet thing.. well…
    Wasn’t there a single entry that was really “cool”? That’s all lame bs, if I had known i’d submitted an entry myself. Probably a blinking LED would top all this stuff!

  6. To post #2, I have another design that allows you to start at a certain point rather than at 0.

    To post #3
    I knew I saw this somewhere before, thanks for digging that up. I remember it from years ago but can honestly say this is from my own devise.

    To post #6 the newer style garage door openers using rolling codes that change everytime the button is pushed, there are like 30 possible codes that can be used at any one time but its out of 128bits or something like that. Sure you could brute force it still but it would take days.

    to post #9
    Maybe you should have submitted something then instead of complaining about other people’s submissions. I never said mine was the first of its kind. While numerous hacks have little real world value, how many hacks actually do? Whens the last time you needed a webcam controlled airsoft gun?

  7. Eurisko – Older garage doors (2003 sounds like a good cutoff date) use a single 8-10 bit code. It’s ok security, but can all possible combinations can be cycled through quickly (like this entry).

    To fix this, you might want to increase the number of bits so it would take longer to guess… but that doesn’t offer any security to people who can record the key over-the-air when you press the transmit button.

    To combat that, rolling codes where developed. The code changes each use (so simple recording won’t work), and it’s hard to predict the next valid code (so that recording + a little processing won’t work). Here’s a good explanation: http://auto.howstuffworks.com/remote-entry2.htm

    Also google keyloq for technical details.

  8. I’ve built these garage door opener tumblers in the past. There are a couple additions I thought of but never made (laziness and liquor prevailed)…
    * Some LED’s inline with the transistors will give a binary readout of the code. Obviously the tumbler will move past the valid code by the time the door starts to raise but it should be close enough to give an approximation of the code to use. If you put a spst button on there to stop the code from rotating you can read the value then work backwards.
    * It’s hard to know how fast you can step through the codes while still knowing the door will open when you get the right one. A way around this – wire 4 universal remotes together. Hardwire the two most significant bits to each combination then slowly work through each step. It’ll try 4 combinations at once.

  9. I can see the hangup, you’ve got one gadget (garage door wedge) that LOTS of people can understand ONE use for, and another gadget (mega something something) that ONE person finds LOTS of uses for… don’t get me wrong, if the jury comes ’round to MY workbench, I’d be hardpressed to describe an actual “use” of any of my creations… just sayin, to each his Leatherman.

    But it is a dilemma that divides the soul of HAD: Dutiful Outfitter of Rare Knowledge -or- Welcoming Instigator of Faithful Involvment

  10. I forgot to mention… garage door openers are long-term investments; they only get upgraded when very broken. Go to an older neighborhood, and I’ll bet 50% aren’t using the rolling codes.

  11. Electronics beginner here:

    What voltage controls this? It appears to be 16 VDC, but can’t quite tell in the schematics. Also, what are the values of C1 and C2?

  12. where would i go to get this silk screened onto a PCB board for me? I would LOVE to build one, but dont have the skills to make one myself. I can solder everything, thats not the issue. its just the traces I cant do.

    thnx in advance to anyone who can help!

  13. Also, I checked out the BOM and found that the 555 timer, the 12-bit counter, and NAND have supply voltages of about 5V. The problem is that there isn’t any handy 5V batts around. I’m thiking of just addding a 1k resistor right after the +’ve terminal to reduce the voltage to 5V (assuming the current draw from the datasheets come out to ~4mA).

    Can someone confirm the required voltage for the circuit?

  14. I was wondering how to use these programs submitted by the two people? I’ve also been looking for the source code for hacking the garage doors

  15. Garage repair man asks:, Why?
    Very good question. Most hackers are angry envious peeps, so they refuse to be honest and say its to F with people. They’ll go on about info is free, yada yada, but its to break into the homes of innocent hard working people; people who earned to live where they live and pay for it. This is where the envy comes in. They’re pissed off jealous jerks. That’s why.

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