The Nickelphone

nickelphone

[Tyler Bletsch] sent us a tip about his new build: a keyboard that redefines “coin-operated.” The Nickelphone can emit square wave tones via a piezo buzzer, but [Tyler] made this 25-key piano as a MIDI keyboard capable of driving a full synthesizer.

He chose an ATMega644 as the brain because it’s Arduino-friendly but has more data pins—32—than the usual ATMega328 chip, which allows him to provide each key with its own pin. Each coin was soldered to its own wire and connects up to a 1MΩ resistor array. Coin-presses are recognized by the simple capacitive sensing technique outlined here, but [Tyler] needed to take advantage of a workaround to accurately detect multiple presses.

Check out [Tyler's] detailed project guide for more information as well as the source code. Check out the video of the Nickelphone after the break, then browse through some other capacitive touch hacks, like the Capacitive Touch Business Card or the Capacitive Touch Game Controller.

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Asynchronous fireflies use few parts

led-firefly

[Karl Lunt] wrote in to share his LED firefly project. His goals for the project were to develop a low-power, low parts count module that can sense when it’s dark and then mimic the blinking patterns you’d associate with its biological namesake.

We like his design which uses a coin cell battery holder as the chassis for the project. The ATtiny13 driving the hardware is held in place by the two power wires. This lets him flash new firmware by rotating the chip and plugging in a little adapter he build. The LED connection might look a bit peculiar to you. It has a resistor in parallel, which doesn’t satisfy the normal role of a current limiting resistor. That’s by design. [Karl] is driving the LED without any current limiting, which should be just fine with the 3V battery and short illumination time of the diode. The resistor comes into play when he uses the LED as a light sensor. Past firefly projects included light dependent resistors to detect light and synchronize multiple units. [Karl] is foregoing the LDR, using the LED with a resistor in parallel to combat the capacitive qualities of the diode. As we mentioned, this senses ambient light, but we’d love to see an update that also uses the LED to synchronize a set of the devices.

Fruit piano uses a different circuit than the Makey Makey

screen

[Hasbi Sevinç] is using perishable goods in his electronics project. The orange, tomato, and two apples seen above act as keys for the virtual piano. The concept is the same as the Makey Makey which is often demonstrated as a banana piano. This implementation uses an Arduino to read the sensors and to connect to the computer running the piano program.

You can see there’s a fair amount of circuitry built on the breadboard. Each piece of fruit has its own channel to make it into a touch sensor. The signal produced when your finger contacts the food is amplified by transistors connected in a Darlington pair. That circuit drives the low side of a optoisolator transmitter. The receiving side of it is connected the I/O pin of the Arduino. You can see the schematic as well as a demo clip after the break.

This use of hardware frees up a lot of your microcontroller cycles. That’s because projects like this banana piano use the timers to measure RC decay. [Hasbi's] setup provides a digital signal that at most only needs to be debounced.

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Conductive filament means printable sensors

The 3D printer world has the creation of plastic trinkets pretty much down pat. The next step, obviously, is the creation of multi-material models, whether they be made of two different colors of plastic, or completely different materials entirely. A few folks from the University of Warwick and GKN Aerospace in Bristol, UK have come up with a way of putting electronic sensors directly into 3D printed objects.

These new sensors rely on a conductive filament custom-made for this study. So far, the researchers have created flex sensors, capacitive buttons, and a ‘smart’ mug that can sense how much water is contained within.

To produce their ‘carbomorph’ filament, the researchers stirred regular old carbon black to a sample of polycaprolactone dissolved in a solvent. After shaking well, the mixture was laid out on a piece of glass for an hour resulting in a thin film that could then be rolled into a 3mm filament. While this is a great way of producing small quantities of carbomorph filament, we’re sure a few Hackaday readers can come up with an easier way of rolling their own conductive filament. Send us a link if you’ve figured out a better way.

Tip ‘o the hat to [Evan] for this one

Bananaphone lets you use fruit and other things as switches

We’re used to [Sprite_TM] rolling out his own hacks hot on the heels of new concepts. Now we’re glad to see that [Jeff Ledger] is doing the same thing here. He was inspired by a Kickstarter project which vows to let you use fruit, clay, and a number of other common (but weird for this use) substances to interface with electronic projects. The mess you see above is the Bananaphone, a synthesizer played with touch sensitive bananas. Think of them as keys on a piano.

The interface works by measuring R/C decay. Each banana is connected to its own input pin on the Propeller board. The capacitance of the bananas rise when you touch them, and this results in a longer R/C decay measurement. Calibrate the target decay period, and you’ve got a reliable capacitive touch sensor which also happens to be delicious. Check out the results which [Jeff] achieves in the video after the break.

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Replicating the fancy touch sensor that uses anything

[Sprite_tm], a name many of you will recognize from these pages, has wasted no time in replicating the latest cool thing in a much simpler fashion. En Garde is a touch sensor that can detect up to 32 different points of contact on… whatever you use as the surface.  He couldn’t sit idly by and let the Disney funded one from yesterday keep the spot light. As you can see in the video, it works pretty well. If he didn’t tell you that his can only detect up to 32 points as opposed to the 200 of the other, you probably wouldn’t even notice the difference.  Of course, [Sprite_tm] also shares how you could easily beef his up to be even more precise. You can also download his source code an schematics from his site and give it a try yourself.

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Reaching out to a touch screen with a microcontroller

We love capacitive touch screens. They’re much more robust than resistive touch screens and if the UI is programmed well they produce a great user experience. But getting your electronics project to interact with one is a bit tough. [RobB] has been experimenting in that area, and managed to build a simple touchscreen actuator for microcontroller use.

In the video after the break you can see his proof of concept. He’s using an Arduino to enter the number 2 on an Android  iOS calculator app once every second. It doesn’t take much to pull off this trick, [RopB] just taped a piece of tin foil to the screen and connected it to the Arduino with a jumper wire. The pin is left floating until a screen tap is needed, at which point it is pulled to ground.

A custom app operating at slow speeds could use this as an input technique. Two pieces of foil (one acting as clock, the other data) would provide a rudimentary serial transfer system.

[Read more...]

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