[Eric] needed a project for his digital logic design class, and decided on a lock that open in response to a specific pattern of knocks. This is a fairly common project that we’ve seen a few builds with ‘knock locks,’ but this one doesn’t use a microcontroller. Instead, it uses individual logic chips.
The lock senses the knocks with a piezo, just like every other build we’ve seen. Unlike the other builds, the knock pattern is then digitized and stored in an EEPROM. [Eric] only used 12 chip for this build, a feat he could accomplish with a few digital tricks, like making an inverter by tying one XOR input high.
We’ve seen a 555-based knock lock before, but getting the timing right with that seems a little maddening. [Eric]‘s build seems much more user-friendly, and has the added bonus of being programmed by knocking instead of turning potentiometers. Check out [Eric]‘s knock lock after the break.
Continue reading “Knock lock with logic chips”
[Dombeef] made a locking enclosure for his sketchbook. The diamond seen in the center of the book is formed by the four sliding parts of the lock. Only with the proper movements will you get the cover open so you can plan your next hack.
He was inspired by this wooden version created by artist [Kagen Schaefer]. There were no tips about how the mechanism was made but a bit of deep thinking led [Dombeef] to discover the secret. Being the papercraft ninja that he is (he makes things like gyroscopes, strandbeests, and claws) this was created using cardstock as the parts. There is a wooden pin on the right that serves as the latch. Each of the four puzzle pieces moves around each other to free a slot from its hold on the notched latch.
There is a diagram showing the parts and their movements in the post linked above. [Dombeef] also mentioned an animated GIF that he promises to publish soon.
[John Boxall] of Little Bird Electronics was thinking about combination locks, and how one might improve or at least change the way these locks work. Traditional combo locks can be implemented in a variety of ways, most of which we are all familiar with. Standard rotary padlock and keypad-based electronic safes work just fine, but he was interested to see how one might implement a single button combination lock.
[John] determined that the best, if not only way, to build this sort of lock would require him to measure button press intervals. In his case he decided to monitor the intervals between his button presses instead, but the concept is the same. He first tested himself to see how accurately he could press and release the button, leaving a one-second space between presses. After looking at the results he determined that he would need to incorporate at least a 10% margin for error into his code in order to compensate for human error.
He then created an Arduino sketch to test his idea, defining a set of key press intervals that could be used to ‘unlock’ his imaginary vault. It worked quite well, as you can see in the video demo below.
Now we’re not suggesting that you lock up your mint condition My Little Pony collection or your illegal arms stash with this type of lock, but it could be useful as an extra failsafe for certain projects/gadgets that you want to keep all to yourself.
Continue reading “Building a single-button combination lock”
Finding alternative ways to unlock doors is a favorite hacker pastime. TkkrLab recently took on the challenge themselves. The hackerspace, which is located in the Netherlands, faced a problem common to communal workshops; how could they manage keyed access for a large number of members? The metal keys for the door are special, and cannot be cheaply duplicated. To further compound the issue, they are not the only tenants in the building so they can’t replace the lock with one that uses less-expensive keys. So they decided to add an electronic solution.
They first looked at a method for electronically opening the door. Often, this comes in the form of an electronic strike, but rather than alter the door jamb, they replaces the latching mechanism. The electronic latch was compatible with the original cylinder, which means the old keys still work in it. You can see the new assembly above. Just to the left of the lock is an iButton reader. We’ve seen this hardware in projects many times before. It’s cheap, and easy to work with. Now TkkrLab issues an iButton to each member, and can keep track of who is coming in door.
Since he was a kid [Giorgos Lazaridis] has always loved the idea of having an electronic door locking mechanism, and now that he has the means, he’s decided to construct one for securing the door to his apartment. He calls the project “simple and cheap”, though we’re not sure about the first part. Taking a look at his very detailed build log, you can see that he has invested quite a bit of time and effort into this impressive project.
Buying an off the shelf product was expensive and not a whole lot of fun, so [Giorgos] disassembled his door’s locking mechanism to see how he might be able to actuate the lock electronically himself. With minimal modifications to the lock, he was able to add a servo which reliably opens the it when triggered.
With the mechanical portion of the project out of the way, he spent a great deal of time working on the door’s electronic components, including the PIC-based controller and capacitive keypad. The keypad proved to be a bit of a problem, but after a few revisions he found a design that was both reliable and pleasing to the eye.
The locking mechanism works pretty well, as you can see in the video below, and [Giorgos] is quite pleased with the results.
Continue reading “DIY servo activated door lock with capacitive touch keypad”
Instructables user [trumpkin] recently built an all-hardware based keypad lock for a contest he was entering, and we thought it was pretty neat. The lock uses mostly NAND gates and 555 timers to get the job done, which makes it a nice alternative to similar software-based projects we have seen in the past.
The lock has 6 keys on the keypad, which is connected to the main logic board. The keycode is set using a series of headers at the bottom of the board, and you get 10 chances to enter the proper code before the board locks up completely. If this occurs, a “manual” reset via a button built into the main board is required before any more attempts can be made.
As you can see in the video below, the lock works quite well, but suffers from one shortcoming. Any permutation of the key code can be used to deactivate the lock, which is something [trumpkin] says he would like to improve in the future.
If you are looking for some more security-related reading, be sure to check out these other hacks we have featured in the past.
Continue reading “Hardware-based security keypad keeps it simple”