Member #134773

Member Since: May 19, 2010

Country: United States


I started playing with electronics in the mid-1960s, and with computers shortly after Neil Armstrong took "one small step". I got a degree in CS in 1980, and started working then as an engineer.

  • One more thought on security: On TV I keep seeing the police saying to NOT leave your garage door open -- that there are criminal types that cruise around looking for open garage doors, and even if someone is in the house, they can still snatch valuables such as golf clubs, tools, etc. I have a friend who keeps forgetting to close her garage door -- I've thought of building a small transmitter of some sort and mounting it on her car, then having a "wall box" of some sort that would detect if the door is open (e.g., a magnetic switch to detect when it's closed) and a receiver to see if the car is in the driveway (it could "hear" the aforementioned transmitter). After sounding some sort of an alarm, after a few minutes, if the car isn't within range and the door is open, it would close the door. (It would also have an "override" for situations where, say, the car was parked out in the street while yard work was being performed.) The cryptography stuff would certainly enhance the "spoofing resistance" of this...

    On a related tangent, I've been thinking about setting up a system with an ESP-8266 and one of the magnetic sensors, using MQTT, to let me know when I forgot to close the garage door at night. I'm also toying with the idea of putting a light sensor of some sort to detect when I left the garage light on.

    Oh, yes: On the suggestion that it's surprising that a "DIY" solution "is much more secure than most commercial-ready products", the "off beat" solution can be more of a deterrant than the "off the shelf" solution to most crackers -- it's much more effective use of their time & resources to crack something that lots of people have than to try to crack something that's "one off". (I've heard generals say that the scariest enemy is the amateur, because they can't predict what the amateur is going to do, whereas with the professional enemy they've got a good idea what his [or her] course of action is likely to be.)

  • Great demo of cryptography, Pete, but IMHO, for most folks it's vast overkill. The typical home robery is going to be done by someone, probably a drug addict, who has neither the financial nor mental resources to "spoof" your garage door opener, but will do a "forced entry". Also, note that this provides no protection from someone breaking into (even a locked) car parked outside and using the remote to open the door.

    On a somewhat related topic, I recall hearing an "urban legend" back in the 1980s that the Secret Service happened to use a frequency that corresponded to the then-current garage door openers, and discovered this when they were preparing for a POTUS visit and using their radios were "saluted" by all the garage doors on the block opening in unison when they keyed up their radios.

    I've put some other comments on the tutorial, but there's one other minor nit: Under "Power Considerations", it says "we'd me more likely" -- methinks it should be "be" rather than "me"...

  • First, I think this project is a really good exercise in using cryptography, but IMHO, it's vast overkill for most folks. If you're truly worried about the security of your home, remember that the vast majority of people who are going to try to break in (a) don't give a damn about whether it's obvious that they've done so (and so will use physical force to gain entry) and (b) don't have the wherewithall, eiither financially or mentally, to defeat the security of the typical garage door opener. (Here in the Phoenix area, there have been multiple recent reports of garage roberies by someone using a large tool to break off the "emergency entry" key-locked handle, and using that to open the door.)

    Second, my understanding of how the "wall button" works is that the ceiling unit provides a (DC) current through the two wires. The LED is across this and lights to give the user "warm fuzzies" that the power is on (and also helps locate the button in darkness). In a single button scenario the switch shorts out the LED and limiting resistor, which the ceiling unit detects, and operates the door. Additional buttons use series resistors to signal their closure. Note that this allows use of the single button remote, or a fancier multibutton remote, with no changes to the ceiling unit.

    Third, I'd be inclined to use a higher number of daily operations. Also, I'd be inclined to have an LED on the remote to give "warm fuzzies" that something is happening when the button is pushed, and absence of it lighting up could indicate "low battery". Also, a more "user friendly" idea would be a provision to charge the battery without disassembly of the remote.

    Fourth, I think you should think about having provision for two (or more) remotes. Think of a two-car garage with only one door opener -- car 1 leaves for work, uses remote 1 to close door. Driver 2 uses wall button to open door, backs car out, uses remote 2 to close door. (This is why the openers come with the ability to support multiple remotes.)

    Fifth, if you are worried about security and install this, be sure to disable the opener's built-in remote. (For at least some, clipping off the antenna wire is probably sufficient.)

  • I don't have time at the moment to go through it in great detail, but it looks pretty good! BTW, it's sort of a "walk down memory lane" (hmm... there's an unintended pun there) as it takes me back to the days when we had to use a computer's "front panel" switches to "toggle" the initial program into it, e.g., to get it to load the assembler, linker, or one's object code off either mag tape or paper tape! Back in those days we had to allocate stack space, heap, program space, arrange the interrupt vectors, etc., by hand for every program.

    One very minor nit to pick (one letter!): Under "How Computers Work (quickly)", in a point numbered 3, it says "volatile memory pace" -- I think it should be "space", not "pace" (don't have time at the moment to do a correction in the Git stuff...

  • Two comments: First, I saw something about one of Tesla's competitors announcing a pickup truck that can turn in its own length -- because it has an independant motor for each wheel. Seems like that capability might be good for your demo -- too bad the price mentioned was $60K...

    Second, I sure hope that Waymo (and that ilk) are using ladar units that aren't as "vertically challenaged" as this one -- but then again, I'm sure thiers are WAY mo[re] expen$ive! (My big complaint with Waymo is that they're not covering my part of Phoenix... yet. Still stuck dodging other cars in my Dodge... :-)

  • I want to wish each and every one at SparkFun a Very Merry Christmas, Happy Hanukkah, Happy Kwanzaa, or what ever holiday YOU choose to celebrate! I am sincerely grateful for your efforts to serve the Maker community, and I thank you!

    And also Happy Holidays to my fellow customers!

  • I, too, would like to see the 5V rail exposed. A few years ago, I built a "Flashy Santa Hat", with a 5V ProMini, addressable RGB LEDs, an accellerometer and ambient light sensor. Last week, my girlfriend wanted to "kiss Santa", and the song I Saw Mommy Kissing Santa Claus ran through my head -- making me think maybe I should add sound to the FSH!

  • I'm hoping this portends use of PIC chips -- many of which have a built-in Real Time Clock Calendar (RTCC).

  • First, it's a great project, and also a great way of keeping stuff out of the landfill!

    I have a few quick comments: First, running the trimpots off the same conductor as the LEDs means that as the brightness changes there can be a variation in the voltage seen by the pots.

    Second, pulling a multiconductor cable can sometimes be enough easier than pulling multiple strands that the extra cost (or hassle) of getting something appropritate might be worth while. (Check hamfests -- you might be able to pick up some "used" cables for not very much money! Even if they have too many conductors, you can consider combining the ones for power and ground, and for this sort of a project, impedance is not much concern.)

    Third, with the computer controlling it, it seems to me that it would be fairly easy to do some IoT type things with this, e.g., timers to make it appear that someone is home, or remote controls...

  • Thanks for sharing, Nate!

    A few years back, there was an "expert" who wrote a book (actually an "e-book") on getting FCC (and other) certifications, and "published" it on one of the "crowd-funding" sites. It'll be a few days before I have time to look up my old e-mail about it.

    The FCC maintains a public, on-line database of the stuff that's been certified. (In this case, use "2ASW8" as the "Grantee" code, and for the "product model" be sure to include that hyphen in "-ART3MIS"!). I've used the database several times to dig up manuals for stuff...

    Anyway, thanks again, Nate, for sharing, and congrats on getting through it!

No public wish lists :(