-In summary, pinpad lock that opens my dorm room door.
i might as well post this little dorm life project before i move back home for the summer. last year i took a class called innovative design in which you come up with a product idea and run it through two prototypes. someone in our group came up with a wireless device that turns the doorknob on your dorm room door via wireless remote. and so keyless dorm room entry device was born. much more complicated than the other team's outlet child proof thing, in wall extension cable, or ipod case on a ziplink thingy. since i designed, built and payed for the prototype and parts i kept it and used it since it actually works.

-the original thingy for wireless entry, pic from last year



then one day this year i forgot my keys in my room. unfortunately my awesome roommate lives with his girlfriend. while that gives me free run of the entire room i learn at the front desk that he has the spare key and never returned it. where as some front desk people are awesome and would get the master keys and go up with me, this guy would rather sit behind his macbook leaving me to wait for my RA to return. while i loitered in our floor's lounge for 3 hours (i took a nap) various ideas of how i could have avoided this issue were imagined. thinking about what an idiot i am for forgetting my keys doesn't count as an idea. the obvious things involved adapting the aforementioned door opener for activation via external means. after acquiring a keypad one day i decided to make the idea reality. the prototype electronics were thrown together and this piece of cardboard with an LCD and keypad was duct taped to my door. it's based on the Atmel AVR and programmed with BASCOM basic compiler. i meant to finalize it with a dedicated board and smaller AVR since it ties up my protoboards but i decided to put a hold on all little projects that would require money until i get a new monitor. it's fun to confront people testing it by quickly opening the door, yelling and waving the sword in the air. unless its an RA or public safety.

-outside my door. the paper above it is the source code, minus the pass code. actually the software has been updated so its alittle different but not by much.




-the servo that pulls the door knob









-the electronics hidden away in my dresser (it's next to the door) the "black box" is the powersupply. it's not as complicated as it looks, just messy. it's really one chip. electronically it is pretty simple and the code was pretty easy to whip up since it's in BASIC form.

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That is really cool nice invention

If it were a little more grungy, that'd be steampunk art!

Wow, nice job man. I get locked out of my room a lot when I'm in college. This may be the best thing for me in the long run If only I had the programming skills to pull it off.

Then again, I am an RA, so I do have access to a master key/spare key to let me in.... That or talk to my other RA friends to let me in. Public safety is nice enough to let any person in their room, and I'm on a name basis with them

Out of curiosity, how powerful is that motor you have in there? I know for the apartment I'm living in next year, the door handle requires a bit of pressure to pull down and open.

you should really clean up those wires.

I bet someone could hack it and get it

it's a Hobbico 1/4 scale servo. probably the cheapest, least powerful of all the 1/4 scale servos in the RC world @ 153 oz. /in of torque. we chose an RC servo because we could adjust the end points in software and they are mechanically easy to use. mainly it was cheap and i could get it at the hobby shop. the other practical option was a car window motor and gear box. if you do tinker with electronics alot you will find that doing things with a MCU and software is easier than a bunch of analog parts. the servo controlled by a MCU was easier and more accurate to control than with a 556 dual timer. so with the bascom compiler you can control i think upto 16 servos with the servo command and one chip where as in the analog world you would have a poopload or parts. if you wanted to do something mundane like blink abunch of lights you would need at least a timing chip and some CMOS counter chip(s) vs one MCU that could do a complex pattern or even dimming. the micro controller does have its limits. making annoying sounds is better with analog parts up until you get really complex, then a MCU controlling a sound chip like a MOS 6581 is on the same skill level as a complete analog synth.

i thought about people attempting to break in via guessing and even less likely, hacking. so i chose 6 digits over the common 4 digit pin. some classrooms on campus have pin code locks and they are 8 digits. if you get the code wrong it displays "denied" and if you get it wrong more than 4 times it disables the lock for 5 minutes so you cant just stand there entering numbers. i might be a little paranoid but the thought of having the ISP pins available on the outside of the door is something that did concern me. the thought of some geeky person coming by with a laptop, ISP dongle and alligator clips is certainly a possibility. the code is on the door along with what chip would be used if i made a board. so they would be able to probe around and discover the SCK, MISO and MOSI pins and reprogram the microcontroller to just have the servo in the open position. of course the code on the door is for an ATmega128 that i use for prototyping where as the final version would use an ATtiny 26 or 28. all i would have to do is not have one of the ISP pins available outside so you cant talk to the thing, probably the serial clock pin. then again the code would be different (different ports used) when going between chips plus without any hints you would be in the dark. plus it's pretty unlikely someone will come to my door with a computer and ISP programmer and try to read off the EEPROM then reprogram my lock. they would have to know how to work with an AVR by what the registers are set to based on what you could dig out of the EEPROM which if they could do, by all means come on in and steal my mini fridge because you earned it. plus i think that when you take the microcontroller course here they teach you to use ARM based hardware in C so they would have to be a real tinkerer, in which case i would probably know who they were since the university isn't huge. it would be easier to come by when i'm in the room and awake since like most people i leave my door open during such time, then you could proceed to slay me and pillage my stuff.

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Can we see a video of it in action?

As a last century man, the first thought I had when I saw your contraption is: anyone who's had two months of tae kwon doe or two glasses of beer could kick that door in one try.

My other observation is that I'd just steal the electronics.

In either case, I used to pop doors like that off the hinges to pull pranks on my friends without much effort. Usually it resulted in something like a room filled with wadded up newspapers and a round of exceptionally pungent cheese.


Thanks for the giggles.

that is great, you need to show me that thing in action some time.

"Denied", gotta love that! But what happens when you get angry and slam the door?

Attemps exceeded is going to suck when you come in drunk one night and press the wrong buttons..... i mean, you would end up sleeping in the hallway :-/

i finally got around to editing the video so here it is

heh nice video, id love to learn that electrical work and coding...Im guessing your major is electrical engineering or something of the sort?

That is just amazing.. you should clean up those cables though, before someone trips on one and pulls everything off the shelf..