Stormtrooper Voice Changer Helmet uses Teensy to Mangle Audio

Halloween has come and gone, but this DIY voice changing Star Wars Stormtrooper helmet tutorial by [Shawn Hymel] is worth a look for a number of reasons. Not only is the whole thing completely self-contained, but the voice changing is done in software thanks to the Teensy’s powerful audio filtering abilities. In addition, the Teensy also takes care of adding the iconic Stormtrooper clicks, pops, and static bursts around the voice-altered speech. Check out the video below to hear it in action.

Besides a microphone and speakers, there’s a Teensy 3.2, a low-cost add-on board for the Teensy that includes a small audio amp, a power supply… and that’s about it. There isn’t a separate WAV board or hacked MP3 player in sight.

Making everything fit nicely in a project takes planning, and not only is the entire system self-contained in the helmet but there’s even ducted blower fans to help stave off heat exhaustion. The whole thing is beautifully done, and nicely shows off the capabilities of the Teensy when it comes to applying the audio filtering abilities.

We’ve seen voice changers using the Raspberry Pi + USB sound board, and even an Arduino + WAV shield in the past, but a Teensy based unit completely self-contained in a helmet is a first.

[via Sparkfun Blog]


Filed under: how-to, wearable hacks

Digipeater hardware build video

Kenneth Finnegan writes:

This is the hardware build of a new digipeater one of my friends asked me to put together for him. The transceiver is a GM300, with a KAM plus TNC modulating it. If we didn’t happen to have a KAM+ on hand, I would have probably used an OT3m from Argent Data.
He’ll provide the computer, but for testing I have it hooked up to a Qotom Q310G4 running Aprx.
As mentioned in the video, when I’m working with CAT5 cable, I love using the GreenLee 4908 toolkit.

Pi Cart: 2,400 Games In One

What’s the quickest way to turn one game into 2,400? Cram a Raspberry Pi Zero running RetroPie into an NES cartridge and call it Pi Cart.

This elegant little build requires no soldering — provided you have good cable management skills and the right parts. To this end, [Zach] remarks that finding a USB adapter — the other main component — small enough to fit inside the cartridge required tedious trial and error, so he’s helpfully linked one he assures will work. One could skip this step, but the potential for couch co-op is probably worth the effort.

Another sticking point might be Nintendo’s use of security screws; if you have the appropriate bit or screwdriver, awesome, otherwise you might have to improvise. Cutting back some of the plastic to widen the cartridge opening creates enough room to hot glue in the USB hub, a micro USB port for power, and an HDMI port in the resulting gap. If you opted to shorten the cables, fitting it all inside should be simple, but you may have to play a bit of Tetris with the layout to ensure everything fits.

Using a Back To The Future game cartridge encapsulates the essence of this project, considering its contents would be nearly science fiction back in the 1980’s — a nice touch. We’ve featured plenty of RetroPie setups — each with their own unique flair — but if you’re looking for a more period appropriate gaming station, you could simply gut an NES for the purpose.


Filed under: how-to, Raspberry Pi

Easy UFO Lights on your Drone for Halloween

Sometimes it’s not so much what you put together, it’s how you use it. The folks at Adafruit have put up a project on how to dress up your drone with ‘UFO lights’ just in time for Halloween. The project is a ring of RGB LEDs and a small microcontroller to give any quadcopter a spinning ‘tractor beam light’ effect. A 3D printed fixture handles attachment. If you’re using a DJI Phantom 4 like they are, you can power everything directly from the drone using a short USB cable, which means hardly any wiring work at all, and no permanent changes of any kind to the aircraft. Otherwise, you’re on your own for providing power but that’s probably well within the capabilities of anyone who messes with add-ons to hobby aircraft.

One thing this project demonstrates is how far things have come with regards to accessibility of parts and tools. A 3D printed fixture, an off-the-shelf RGB LED ring, and a drop-in software library for a small microcontroller makes this an afternoon project. The video (embedded below) also demonstrates how some unfamiliar lights and some darkness goes a long way toward turning the otherwise familiar Phantom quadcopter into a literal Unidentified Flying Object.

While it might be tempting to buzz people to show off the effect on Halloween, flying over or around people with what is essentially an airborne surprise blender is a needless risk. But you don’t need people around; drones (and some cleverness) have opened many doors for the amateur film crowd.


Filed under: led hacks

Train Time Ticker Will Save Your Morning Commute

The fatal combination of not being a early riser and commuting to work using public transit can easily result in missed buses or trains. Frustrated with missing train after train while fumbling with a complicated transit schedule app, [Fergal Carroll] created a Train Time Ticker to help his morning routine run right on time.

A Particle Photon hooked up to a 2.2″ TFT screen — both mounted on a breadboard with a button — fit the purpose tidily. Weekday mornings, the Ticker pulls — from a server he set up — the departure times for the specific station and platform along [Carroll]’s commute every three minutes; at all other times, the Ticker can be manually refreshed for any impending trips.

[Carroll] has provided a clear, step-by-step guide on how to wire and program your own device — subbing in transit information relevant to you, of course. Over a month of use, it has resulted in far fewer missed trains, and has probably saved some headaches in the mornings to boot!

We’ve featured some other fancy ticker projects on Hackaday — this one will keep you abreast of the latest bitcoin fluctuations, while another is a spiffy way to print off your emails.


Filed under: clock hacks, how-to, transportation hacks

Guide for BMP180 barometric sensor with Arduino

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A how-to on using the BMP180 barometric sensor with the Arduino from Random Nerd Tutorials:

The BMP180 barometric sensor (model GY-68) is the one in the following figure (front and back view). It is a very small module with 1mm x 1.1mm (0.039in x 0.043in).
It measures the absolute pressure of the air around it. It has a measuring range from 300 to 1100hPa with an accuracy down to 0.02 hPa. It can also measure altitude and temperature.
The BMP180 barometric sensor communicates via I2C interface. This means that it communicates with the Arduino using just 2 pins.

Light intensity meter using AT89C52 microcontroller

LDR

AM Bhatt over at Engineers Garage writes:

In the given project, LDR is used to measure light intensity inside the room. With a minor change in the circuit, it can be used to measure outdoor light intensity also. It uses microcontroller AT89C52 and LCD to display light intensity. It also indicates how much light inside room like “full light”, “good light”, dim light” etc. However, microcontroller cannot detect the change in resistance directly. LDR has to be given biasing voltage along with pull up or pull down resistance so that change in resistance is converted into change in voltage. The change in analog voltage is converted into digital equivalent using ADC and this digital value is read by microcontroller. Let us discuss this in somewhat more detail manner.

More details at Engineers Garage homepage.

Check out the video after the break.

The Little Things I Didn’t Know About Small DC Motors

We’ve all taken apart a small toy and pulled out one of those little can motors. “With this! I can do anything!” we proclaim as we hold it aloft. Ten minutes later, after we’ve made it spin a few times, it goes into the drawer never to be seen again.

It’s all their fault

It always seems like they are in everything but getting them to function usefully in a project is a fool’s errand. What the heck are they for? Where do people learn the black magic needed to make them function? It’s easy enough to pull out the specification sheet for them. Most of them are made by or are made to imitate motors from the Mabuchi Motor Corporation of Japan. That company alone is responsible for over 1.5 billion tiny motors a year.

More than Just the Specs

In the specs, you’ll find things like running speed, voltage, stall current, and stall torque. But they offer anything but a convincing application guide, or a basic set of assumptions an engineer should make before using one. This is by no means a complete list, and a skip over the electrics nearly completely as that aspect of DC motors in unreasonably well documented.

The paint mixers high running speed and infrequent use make it a decent candidate for hooking directly to the motor.
The paint mixers high running speed and infrequent use make it a decent candidate for hooking directly to the motor.

The first thing to note is that they really aren’t meant to drive anything directly. They are meant to be isolated from the actual driving by a gear train. This is for a lot of reasons. The first is that they typically spin very fast, 6,000 – 15,000 rpm is not atypical for even the tiniest motor. So even though the datasheet may throw out something impressive like it being a 3 watt motor, it’s not exactly true. Rather, it’s 3 N*m/s per 15,000 rotations per minute motor. Or a mere 1.2 milliwatt per rotation, which is an odd sort of unit that I’m just using for demonstration, but it gives you the feeling that there’s not a ton of “oomph” available. However, if you start to combine lots of rotations together using a gear train, you can start to get some real power out of it, even with the friction losses.

The only consumer items I can think of that regularly break this rule are very cheap children’s toys, which aren’t designed to last long anyway, and those powered erasers and coffee stirrers. Both of these are taking for granted that their torque needs are low and their speed needs are high, or that the motor burning out is no real loss for the world (at least in the short term).

This is because the motors derate nearly instantly. Most of these motors are hundreds of loops of very thin enameled wire wrapped around some silicon steel plates spot welded or otherwise coerced together. This means that even a small heat event of a few milliseconds could be enough to burn through the 10 micrometer thick coating insulating the coils from each other. Practically speaking, if you stall a little motor a few times in a row you might as well throw it away, because there’s no guessing what its actual performance rating is anymore. Likewise, consistently difficult start-ups, over voltage, over current, and other abuse can quickly ruin the motor. Because the energy it produces is meant to spread over lots of rotations, the motor is simply not designed (nor could it be reasonably built) to produce it all in one dramatic push.

Making Contact

Pololu has the clearest picture of the different kind of brushes inside these small motors.
Pololu has the clearest picture of the different kind of brushes inside these small motors.

This brings me to another small note about these tiny motors. Most of them don’t have the carbon brushes one begins to expect from the more powerful motors. Mostly they have a strip of copper that’s been stamped to have a few fingers pressing against the commutator. There’s lots of pros to these metal contacts and it’s not all cost cutting, but unless you have managed to read “Electrical Contacts” by Ragnar Holm and actually understood it, they’re hard to explain. There’s all sorts of magic. For example, just forming the right kind of oxide film on the surface of the commutator is a battle all on its own.

It’s a weird trade off. You can make the motor cheaper with the metal contacts, for one. Metal contacts also have much lower friction than carbon or graphite brushes. They’re quieter, and they also transfer less current, which may seem like a bad thing, but if you have a stalled motor with hairlike strands transferring the pixies around the last thing you’d want to do is transfer as much current as possible through them. However, a paper thin sheet of copper is not going to last very long either.

So it comes down to this, at least as I understand it: if bursts of very fast, low energy, high efficiency motion is all that’s required of the motor over its operational life then the metal strip brushes are perfect. If you need to run the motor for a long stretches at a time and noise isn’t an issue then the carbon brush version will work, just don’t stall it. It will cost a little bit more.

Take Care of Your Tiny Motors

Here is one of these can motors being restrained properly. Only torque on the case itself is restrained. The motor is otherwise free to move.
Here is one of these motors being restrained properly. Only torque on the case is restrained. The motor is otherwise free to move.

To touch one other small mechanical consideration. They are not designed to take any axial load at all, or really even any radial load either. Most of them have a plastic or aluminum bronze bushing, press-fit into a simple stamped steel body. So if you design a gearbox for one of these be sure to put as little force as possible on the bearing surfaces. If you’ve ever taken apart a small toy you’ve likely noticed that the motor can slide back and forth a bit in its mounting. This is why.

Lastly, because most of these motors are just not intended to run anywhere near their written maximum specifications it is best to assume that their specifications are a well intentioned but complete lie. Most designs work with the bottom 25% of the max number written on the spreadsheet. Running the motor anywhere near the top is usually guaranteed to brick it over time.

These are useful and ubiquitous motors, but unlike their more powerful cousins they have their own set of challenges to work with. However, considering you can buy them by the pound for cheaper than candy, there’s a good reason to get familiar with them.


Filed under: Curated, Engineering, news