Quadcopters Go Inverted By Reversing Their Motors

November 26, 2013 by Adam Fabio 17 Comments

Inverted Quadcopter? That generally means a crash is soon to follow. Not so for a new crop of quadcopter fliers. These new quadcopters are capable of sustained inverted flight. We’ve seen inverted quadcopters before here on Hackaday. However, previous inverted quadcopters always used collective pitch to control the thrust produced by the blades. Collective pitch on a quadcopter is much simpler than it is on the main rotor of a traditional helicopter. R/C and full-scale helicopters mix collective and cyclic pitch to articulate the main rotor blades. A quadcopter only needs the collective portion, which is similar to a traditional helicopters tail rotor mechanism, or a variable pitch prop on an airplane.

These new quadcopters are using a much simpler method of flying inverted: Spin the motors backwards. Quadcopters control their flight by quickly varying the speed of rotation of each motor. Why not completely reverse the motor then? Today’s brushless outrunner motors have more than enough power to quickly reverse direction. The problem becomes one of propellers. Standard propellers are designed to create thrust in one direction only. Every quadcopter uses two clockwise rotation and two counterclockwise rotation propellers. Propellers will generate reverse thrust if they are spun backwards, however they will not be as efficient as they would when spinning the direction they were designed for. The quad fliers have found a partial solution to this problem: Remove the curve from the blade. R/C propeller blades are sold by diameter and blade pitch. The pitch is a measure of the angle of attack of the blades. R/C blades also have an airfoil style curve molded into them. Removing this curve (but not changing the pitch) has helped the problem.

This final problem is control systems. Since quadcopters already are relying on computer control for basic flight, it’s simply a matter of loading custom firmware onto your flight board to support motor rotation reversal. Speed controls also have to be capable of reverse rotation, which means new firmware as well. We’re curious to see how the quadcopter community settles on the control systems for inverted flight. The R/C helicopter community went through several iterations of control systems over the years. At one point they were using “Invert switches” which reversed controls as well as handled the collective pitch changes. As time went on, these switches fell out of favor and are now known as “Crash switches” due to the result of accidentally hitting one while flying, or before engine start.

[Thanks Marc]

JTAGulator Finds Debug Interfaces

October 2, 2013 by Adam Fabio 25 Comments

jtagulator

[Joe Grand] has come up with a tool which we think will be useful to anyone trying to hack a physical device: The JTAGulator. We touched on the JTAGulator briefly during our DEF CON coverage, but it really deserves a more in-depth feature. The JTAGulator is a way to discover On Chip Debug (OCD) interfaces on unfamiliar hardware.

Open any cell phone, router, or just about any moderately complex device today, and you’ll find test points. Quite often at least a few of these test points are the common JTAG / IEEE 1149.1 interface.

JTAG interfaces have 5 basic pins: TDI (Test Data In), TDO (Test Data Out), TCK (Test Clock), and TMS (Test Mode Select), /TRST (Test Reset) (optional).

If you’re looking at a PCB with many test points, which ones are the JTAG pins? Also which test points are which signals? Sometimes the PCB manufacturer will give clues on the silk screen. Other times you’re on your own. [Joe] designed the JTAGulator to help find these pins.

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Turning Anyone Into A Casuality

August 16, 2013 by Brian Benchoff 8 Comments

Triage

EMTs and other first responders don’t just sit around waiting for a disaster to happen. If they need to train for a disaster – environmental, terrorist, or otherwise – they put together a mass injury simulation, or their version of a war game. As you can imagine, coordinating one of these simulations is a nightmare, but [David] came up with a way to simulate a casualty with a few XBees, a Parallax Propeller, and a few RFID cards.

This triage training simulator consists of an ‘acting coach’ on each simulated victim that includes a speech-to-text module that speaks instructions into the actors ear, a pulse simulator and a readout for vital signs that correspond to twelve major injuries. When an EMT triages a victim, they swipe an RFID card for each medical procedure they perform – intubating is one card, while a bandage is another – and all this is sent back to the coordinator’s tablet.

The coordinator has direct control over each of the actors through a two-way radio link, and can initiate changes in each victim, monitor a paramedic’s responses, and “escalate” the situation by setting off another simulated bomb.

All this is created with off-the-shelf hardware, vastly reducing the cost of this type of training device. An amazing application of what we usually consider to be just robot parts, and we’re happy for [David] to share it with us.

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Pill Dispenser Tattles To The Internet When You Don’t Take Your Pills

August 9, 2013 by Mike Szczys 16 Comments

Here’s another entry in the Parallax microMedic 2013 contest. [Tim] calls it his Propeller-based Internet Logging Pill Dispenser (PDF file), or P.I.L. Box for short.

The hardware is a base unit into which a normal plastic pill organizer is placed. We like this design, as many pharmacies will fill pill boxes for you and this doesn’t complicate that process. You simply pull out the correct box at the beginning of the week and put it in the base unit. You can see one white LED is shining on the Monday slot in the box. This lights up starting an hour before the set pill taking time. This way if you walk by it reminds you. There is also a voice tailor made to scare the elderly that comes out of the speaker, and a simple messages spelled out on the set of seven segment displays. The base unit detects when you press the button to open the pill box and counts that as a properly administered dosage.

Now, if you forget to take the pill it’s not a good thing. The server, which is running on the laptop, will rat you out. It uses the Twitter API to alert whomever is following it — meant for a relative or caregiver — that a dosage was missed. Let’s hope they’re good at keeping up with their Twitter feed!

We remember seeing one other microMedic entry so far, this heart-shaped heart simulator. But we’re going to look around and see how many other good ones we’ve missed.

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Rekindling Forth With A Propeller Jupiter Ace

July 28, 2013 by Brian Benchoff 26 Comments

Jupiter

The Jupiter Ace was a small membrane keyboard, cassette tape drive computer akin to the ZX Spectrum released in 1982. Priced at £90, it was a little more expensive than its home computer contemporaries, but had a very interesting feature: instead of BASIC, the Ace ran Forth. This interpreted stack-based language is far more capable than the BASIC variants found on home computers of the day, but unfortunately the Ace failed simply because Forth was so foreign to most consumers.

Not wanting to let a good idea die, [prof_braino] is bringing Forth back into the modern age. He’s using a Parallax Propeller to emulate a simple home computer running Forth. Instead of a book-sized computer, the new Propeller version runs on a single chip, with 8 CPU cores running 24 times faster than the original, with 32 times more RAM and an SD card for basically unlimited storage.

Heart-shaped Heart Simulator

July 27, 2013 by Brian Benchoff 12 Comments

Heart

A few years ago, [Addie] over at Tymkrs put together a spooky little Halloween project: a small Propeller board that emulates the electrical signals in a heart. As a cardiac nurse, she thought her project could use a little improvement, and after two years she’s finally done. It’s a heart-shaped board that simulates electrical signals moving through the heart.

There are several key areas that conduct electrical signals through the heart – the sinoatrial node, atrioventricular node, and bundle branches all work like players in an orchestra to keep a heart beating like it should. If something goes wrong with one of these, the heart goes into tachycardia or fibrillation – not good, by any measure. [Addie]’s board simulates all the different ways a heart can go wrong with LEDs standing in for the electrical signals in a real heart. The name of the game here is to look at the LEDs and tell what state the heart is in.

The PCB heart is just one part of [Addie]’s heart simulator. The simulated heart can also plug into a neat little heart-shaped project box wired up with a solenoid, LCD display, headphone jack, and other electronics to turn this electronic heart into a complete study tool for heart rhythms. The nurses in [Addie]’s unit love the thing, and it looks like [Addie] might have a real cardiac training tool on here hands here.

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Building A Synth On A Breadboard

June 21, 2013 by Brian Benchoff 12 Comments

synth

Building an analog synth is a challenge, but with the [Tymkrs] protosynth, it’s easier than ever. It’s a 25-key keyboard attached to a stack of solderless breadboards to make analog synth prototyping a snap.

Earlier, [Tymkrs] acquired a whole bunch of solderless breadboards and decided to put them to use by making a component-level modular synth. The earlier incarnation tied each key on the keyboard to a few wires behind the breadboard and tied them in to a shift register so they could be read with a Propeller dev board loaded up with a Commodore SID emulator. The new version keeps the very clean through-the-back keyboard connector, but this time the [Tymkrs] are adding a few more components that add a sequencer setup and a rotary encoder.

The eventual goal for this really cool breadboard synth is to explore the world of Moogs, Arps, and other analog synths easily on a breadbaord. The [Tymkrs] have already put together a breadboard-compatible low pass and high pass filter. While there’s still a lot of work to be done to make an analog synth a reality, the [Tymkrs] are off to a great start.

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