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Archive: Electronics

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September 25, 2007

Using the Wii Remote to correct perspective in digital photos

Daniel M. German found a way to automate perspective correction and projection adjustments for his wide angle photography. He does this by using a Wiimote to record the pitch and roll of the camera at the time a photo is taken. This information can then be fed directly into panotools, instead of manually entering control lines and processing the images to calculate these tilt values after the fact.

I modified an open source DarwiinRemote to record inclination. It happens that if you keep the WiiR in a stationary state, its three accelerometers can be used as two inclinometers. Fortunately most of the time, when one takes a handheld photo, one keeps the camera steady. Steady enough to read the inclination of the WiiR.
I also modified the driver to record the reading from the accelometers, the estimated inclinations, and the timestamp. I would then use the timestamp to match the images from the camera to the readings from the WiiR.

This is a cool idea. I would not be surprized to find high end cameras internally recording and stamping this information into photographs in the near future. A lot of consumer cameras already support panoramic stitching, so with digital accelerometers and tilt sensors being as cheap as they are, why not internally support adjustments like perspective correction or projection remapping?

Using the Wii Remote to correct perspective - Link

September 21, 2007

Recycle an old floppy connector as an SD card socket

You've probably got an old floppy drive edge connector or two lying around from an old computer. You can save a bit of money and recycle these as SD/MMC card sockets for your electronics projects. The card can then be used in MMC mode by just wiring up a few I/O pins.

Rob Wentworth documented using this faux-sd floppy connector to add SD support to his WRT54G router. If you're using the DDWRT or OpenWRT firmware for your Linksys, this hack can give you a huge upgrade with more data storage space and swap ram.

SD/MMC card fits in floppy edge-connector - Link
Adding an MMC/SD Card to the WRT54G - Link

September 16, 2007

Hacking the Hot Wheels Radar Gun

Ed Paradis has put some thought into a couple of hacks for the Hot Wheels toy radar gun:

The Hot Wheels Radar Gun is a real radar gun currently (Feb 2007) available from Walmart and other retailers for about $30 (USD). It is a real radar gun, operating at 10.525 GHz capable of clocking cars, people, pets, and toys.
But before you can play with it, you've got to get the thing open! Here are some pictures of me taking the thing apart.

You can use the radar to detect the speed of moving objects, but Ed also posted some semi-successful (and some not-so, but worth reading) experiments with using the device in a custom circuit to detect the distance of objects for robotic projects. It's also worth noting that the LCD can be repurposed as a display output for your other electronic gizmos. For 30 bucks, it's a pretty good collection of useful robot parts.

Hacking the Hot Wheels Radar Gun - Link

September 12, 2007

HOWTO: Make a Wiimote peripheral - wireless Nunchuck anyone?

The Wii Nunchuck communicates with the Wiimote over I2C, constantly sending little 6-byte packets that describe the anolog stick, accelerometer, and button values.

You might remember that Brian posted about how you can hook the Nunchuck up to an Arduino board and read accelerometer data from it. Chad from Windmeadow Labs, who was responsible for this hack, also put together a howto describing how you can use an Adruino to mimic a Nunchuck, interfacing directly with the Wiimote.

So, you can connect an Arduino to a Nunchuck to read data from it. You can connect an Adruino to the Wiimote to send data to it. If only you could make those two Arduinos talk to eachother... Hold the phone! I posted about a $14 RF serial module from SparkFun that will let you do just that!

It'd be a little clunky because of the size of two chubby Arduinos, but if you can't wait for Nintendo to release a wireless Nunchuck to help you with your WiiSports Boxing habit, all the bits and pieces are here for you. You can get Freeduino bare bones kits pre-assembled from Modern Device for $22 each, so the total would come to just under $60.

$60 of purely awesome wireless Mii punching fury.

There is one caveat: the RF link would not be fast enough to communicate sample data from the nunchuck as fast as it is read by the Wiimote. There's a possible solution, though, for those of you who'd like to give it a try. The Nunchuck board can sample the button and accelerometer data and send it over the air at 2400 baud. The Wiimote-connected Arduino can store the last-received state and just keep sending that same data to the Wiimote at fast I2C speed until the next update is received from the RF connection. I'm not sure how noticeable the sensitivity loss would be, but you should still be able to have a resolution of about 40 sensor updates a second.

Anyone with a couple spare Arduinos want to give this a shot and share the details?

Connect an Arduino to the Wiimote as a perhiperal - Link
Hook your Wii nunchuck up to an Arduino - Link
RF-enable your microcontroller projects - Link
Nunchuck communication details - Link

September 10, 2007

Eyelash switch: cyborg-style human interface device

With some conductive fabric and spirit gum, you can make a simple binary switch that attaches to your eyelids. Andrew Schneider used some of these to make a polaroid camera that takes a snapshot when you blink.

When I first saw these, I was reminded of cyborgs in television and film and how they typically exhibit facial twitches when receiving data or jacking in to the network brain. I always thought the apparent "glitch" was sort of a stupid film device, but mabe it's not that far from the future truth. Left wink, change music track. Right wink, shoot photo with the camera tilak in your forehead. Triple-blink, stimulate adrenal gland to release epinephrine. Eyes closed for one minute, dose of melatonin.

Experimental Device for Performance: Eyelash Switch - Link

September 9, 2007

Arduino Diecimila Upgrade

David sent us an easy upgrade for the Bare Bones Arduino that will give it a couple cool features released with the new Diecimila Arduino, namely the ability to auto-reset after a code upload and a firmware update that will get the board running in 2 seconds instead of 10.

With help from Paul Badger of Modern Device Company and Brian of the Freeduino project this article will show you how to modify the Bare Bones Arduino board to make it compatible with the new Diecimila Arduino. No more pressing the reset button to load your code and no more long waits to see if it runs.

You can do the same with the Arduino NG boards as well. Both mods are just a simple solder job with a 0.1uF capacitor. If you tinker around with Arduino projects, this could be a huge development time-saver.

Bare Bones Arduino Diecimila Mod- Link
Upgrading an Arduino NG to Auto-Reset - Link

September 4, 2007

Fire and robots

Fire and robots. Robot love. Burnination. I came across a couple of pyro-robot soulmates today.

Flameosapien is our familiar buddy, slightly modified with a remote operated flamethrower. The Robosapien V2's remote was modified with an additional 4 channer transmitter. Gas flow is adjusted by a small servo and ignited with a BBQ lighter.

His more autonomous counterpart is a Wiimote controlled robotic firefighter. The Wiimote's IR sensor is used for detecting a fire source (such as a candle) and it relays commands between an arduino board and a nearby computer. It's a pretty simple set-up: the robot turns toward the flame, spins a fan, and drives toward the fire. Crude, maybe, but I dig how the Wiimote is being used as a communication channel for the arduino. This might be a simple way of adding bluetooth capability to your own robot project.

Flameosapien - [via] Link
Wiimote Controlled Firefighting Robot - Link

August 28, 2007

Soldering with a graphite pencil and car battery

Here's a weird arc-welding meets soldering hack. You can use a 12 volt car battery (or charger) and a length of graphite pencil to solder connections. The graphite is connected to one jumper cable and a length of solder to the other. Touching them both to the connection closes the circuit, heats up the connection point, and melts the solder. I'm guessing this works best if you connect the graphite and solder to either side of the component connection, which would conduct over the component lead, heating it and causing the solder to wick into the joint.

I'm not sure how well this works or how hard it is on your battery, but it looks like it might be a good way to solder small and difficult connections without overheating components.

Anyone care to chime in on the effectiveness of this or any specific precautions that should be taken?

Graphite Pencil Soldering - Link

August 13, 2007

HOWTO: Power Over Ethernet on a Linksys WRT54GL router

With a little quick soldering, you can convert your Linksys router to receive it's DC power through the ethernet uplink instead of through a separate power cable. This is incredibly useful if you want to place your router above the ceiling or in a location that is inconvenient to get power to.

After the conversion, the 12v DC from the power adapter is sent along the unused blue and brown ethernet pairs. You'll be able to place your router over 500ft from the switch without the voltage dropping below the 5.5v that the router needs to operate.

HOWTO: WRT54GL DIY Internal POE! (Google cache) - Link

August 9, 2007

HOWTO: sort grab-bag electronics

David from uC Hobby writes:

How-to sort a 1 pound grab-bag of small electronic components. I sort through one of the $1 grab-bags I purchased at the Austin Summer fest 2007 HAM meet up. The reason these grab-bags are cheap is that you have to do a lot of work to make the collection of parts useful. I explain my method and give the tally for the parts.

For some reason, this always brings back memories of dumping and sorting big plastic bags of Lego Technic parts.

Grab Bag Sorting Howto - Link

July 26, 2007

Microcontroller basics: using transistors to amplify current

To control a lot of components, especially motors, physical devices or bright LEDs, you typically need to accommodate more current than your typical microcontroller can provide. Eric Wolf wrote a nice introduction for using transistors as a current amplifier to solve this common scenario.

In regard to current capability, generally speaking, most microcontrollers will only source around 20 mA or less (usually less) of current before you start running into problems. This is less than the amount of current used to power a super bright LED at maximum intensity (the ones I use run around 30 mA, a lot can run less). There comes a time in every man and woman's life when they just need more power.
A Bipolar Junction Transistor has many different functions and applications in a circuit. It can be used in an amplifier configuration, a device to regulate the flow of current (think of a valve on a water pipe), or, in our case, a switch. For all intents and purposes, this "switch" can be referred to as a current amplifier.

If you want to control larger motors, you'll probably need to use a device called a Darlington Pair, which is actually a combination of two transistors. These can be purchased as a single package component which simplifies the wiring a bit.

If you're interested in controlling motors from a microprocessor, you might also want to check out an article I wrote about building an h-bridge circuit. An h-bridge is a simple circuit that you can build that will allow you to control a motor, both forwards and backwards, with the output on two IO pins. It uses a number of Darlington transistors in combination to both power the motor and to switch the direction of the current based on the input from the two IO pins. In my case, I used an h-bridge to control an RC car with a Basic Stamp microcontroller.

Resources:
Use a Transistor as a Current Amplifier - Link
Control a Motor with an H-Bridge - Link

July 7, 2007

HOWTO: Arduino LCD interfacing

David from uC Hobb writes:

I have scrounged up several LCD displays and wanted to use one with the Arduino. At the very least I wanted to test the displays. For future projects with the Arduino having a LCD display could be very handy so for this reason it is a good first project as well.

The article walks you through using a basic 8-bit interface and provides links to a number of references for LCD/Arduino interfacing and programming - Link.

Related:
Physical computing with the Arduino - Link
Hook your Wii nunchuck up to an Arduino - Link

June 27, 2007

Physical computing with the Arduino

The Arduino platform is an affordable way to start monkeying around with microcontrollers, embedded programming, and physical computing. Hackszine reader scjohannes sent us this link to a Arduino "getting started" guide on Instructables:

Do you wish to earn your geek card - pronto? Lets get started! This guide will start you on the path to the dark side using the open source Arduino development and prototyping platform. It will introduce you to microcontrollers, get you started with a platform for physical computing and give you the confidence to create technological marvels. It is open source, inexpensive and a blast to learn.

As luck would have it, Arduino kits just became available at the Maker Store! If you've got any fun Arduino projects or hacks that you'd like to share, please shoot my an email or add it to the comments.

How to have fun with Arduino (and become a Geek in the process) - Link
Ardiuno @ Maker Store (in the Make:it kits section) - Link

June 24, 2007

Battery conversion hacks

Have you ever needed a D battery in a pinch, but could only find Cs? Since AAA, AA, C, and D batteries are all 1.5 volt cells, they are electronically interchangeable. They differ only in physical size and energy storage capacity. So, if you're in a pinch, you can cobble together an adapter with a few quarters or other suitable conductive material.

Even a 9-volt battery is made up of 6 1.5 volt cells, which are a bit smaller than a AAA (they are actually called AAAAs!). This could come in handy if all you can find is a 9 volt and you really need a AAA for your TV remote... You'll just have to spend some time cracking open the 9 volt case with a pair of pliers to get at the little cells inside.

Quick hack: The $1 C-to-D adapter -Link
9 volt to AAA conversion - Link

May 23, 2007

Increasing your car remote's range with your head

According to the completely authoritative sources of youtube and metacafe, you can extend the range of your car remote by holding the remote to your head. It's easy enough to test, and if it works it could come in handy for finding your car in the parking lot. So far, I've found two videos demonstrating the hack, and both use a slightly different method.