Knock lock balks knock, uses CapSense without shock

[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.

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[RobB’s] house has no light switches

So [RobB] wanted to take out all the light switches in his house. His plan was to replace them with a system that could be operated from his smart phone. But his wife insisted that there still must be some way to control the lighting directly — we have to agree with her on that one. The solution was to develop a system that switches the lights via a touch sensor or by Bluetooth.

The touch part of the project is pretty easy. He coated the back of a blank outlet plate with tin foil and hooked it to a microcontroller with a couple of resistors. He’s using an ATtiny85, which can be programmed using Arduino sketches, so the software side is made easy by the CapSense Library. The chip also uses the software serial library to communicate with a Bluetooth module. You can see the result of both in the demo video after the break.

Of course you need to throw a relay in there to switch mains, and find a way to power the uC and Bluetooth module. [RobB] went with a tiny plug-in USB power converter and managed to fit everything in a single-gang switch.

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Piano Box is a digital synthesizer made of paper

We love the look of this papercraft piano which [Catarina] built along with some friends at NYC Resistor, a hackerspace in the big apple. It starts off as a cubic black box with a white top. But just lift that top as [Catarina] does in the video after the break and three of the sides fall flat to reveal a pair of speakers and the single-octave keyboard.

The key’s don’t move when you press them. Instead, she decided to use the CapSense Arduino library to implement touch sensitive keys. Each key is made up of a plane of copper foil tape, with a strip of tape running back to the center of the box where it is interfaced with an Arduino Mega hidden there. The Tone library produces the waveforms which are played by the speakers, and a set of LEDs on the upright side of the box illuminate the keyboard diagram as you press each key. You can see that there are short white bars on that display which correspond to the black keys on the keyboard.

If you take a look at the code, you’ll see the libraries really make the code for the project simple.

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Simple touch sensors with the Arduino CapSense library

Ever thought of using touch sensors on your projects but didn’t because it would be too much work? [Paul Stoffregen] proves that it can be pretty easy if you use the CapSense library for Arduino. Here he’s created three touch sensors, connecting them to the Teensy microcontroller with two resistors each. The larger resistor (looks like 4.7 megaohms here) sends a signal through the copper pad which is read by the secondary pin. Here that pin is protected from electrostatic discharge with the 1k resistors. The microcontroller takes a reading by measuring how long it takes the voltage to change on the input pin.

Since the CapSense library takes care of the timing involved in these readings, all you have to do is decide how your program will react to the numbers that are coming in. In the video after the break [Paul] is echoing the timing figures back through the serial monitor to get an idea of what the data looks like. He experiments with touching the copper directly, and touching it through a piece of clear tape.

We’ve seen the CapSense library at work before in this interactive exhibit piece.

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