[Rob Hemsley] sent in an update to an RFID-based door lock. Previously, if you wanted to enter the MIT media lab, a RFID-enabled card was required to get in. Now, with [Rob]’s update, you only need to tap the door handle in a ‘secret’ pattern.
The earlier RFID-enabled build used about $80 in hardware, not a very economical solution. The new touch-based solution only uses an Arduino and servo, making the build much cheaper.
The touch sensitive lock uses the CapSense Arduino library. By turning the door handle into a touch sensor, [Rob] allowed a secret code to be saved in the EEPROM. Repeating this sequence when the door is locked sends power to the servo, unlocking the door.
A very cool build that’s also a little more secure than the traditional, audible knock lock. Check out the video after the break.
Continue reading “Knock lock balks knock, uses CapSense without shock”
[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”