ContactKey: A portable, battery-powered phonebook

contactKey

Although it’s still a prototype, [Russell] tipped us off to his battery-powered device for storing your contacts list: ContactKey. (Warning: Loud sound @ beginning). Sure, paper can back up your contact information, but paper isn’t nearly as cool to show off, nor can it receive updates directly from your Android. The ContactKey displays a contact’s information on an OLED screen, which you can pluck through by pressing a few buttons: either ‘Up,’ ‘Down,’ or ‘Reset’. Although the up/down button can advance one contact at a time, holding one down will fly through the list at lightning speed. A few seconds of inactivity causes a timeout and puts the ContactKey to sleep to conserve battery life.

This build uses an ATMega328 microcontroller and an external EEPROM to store the actual list. [Russell] wrote an Android app that will sync your contact list to the ContactKey over USB via an FTDI chip. The microcontroller uses I2C to talk to the EEPROM, while an OLED display interfaces to the ATMega through SPI. We’re looking forward to seeing how compact [Russell] can make the ContactKey once it’s off the breadboard; the battery life for most smartphones isn’t particularly stellar. Phones of the future will eventually live longer, but we bet it won’t be this one.

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Graffiti briefcase for stealth tagging

We’re floored by painter and engineer [Bob Partington’s] graffiti briefcase, which proves how well art and tech can complement one another. Fear not, Arduino haters, [Bob]’s case is an analog dream: no microcontrollers here.

The guts consist of 2 components: a linear drive system and a trigger assembly. The former takes advantage of a small RC motor with a chain drive which slides the can’s mounting unit along two stainless steel rods. The latter includes a custom wound solenoid plugged into a 24V cordless drill battery, which slams down 5 pounds of force onto the can’s nozzle to fire the paint.

This all fits into an otherwise inconspicuous looking briefcase to provide some urban camouflage. The final component is a stencil, which slides into a rectangular hole on the bottom of the case. The paint can sprays downward through the stencil and tags the ground at the touch of a brass button located near the handle.  [Bob] has plenty of other cool inventions you should check out that are less illegal. Or, stick it to the man by automating your tagging with Time Writer.

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Fail of the Week: Switched-mode PSU camera battery replacement

We really wanted this week’s Fail to work. [Michael] wanted more juice for his Nikon D3100 camera. The idea he had was to replace the cells of the battery with a Buck converter and add leads for an external battery. This opens up the possibility of running from a wide range of voltage sources; an attractive prospect for devices using specialize batteries. Specifically, he wanted to swap out the stock 7.4V 1030 mAh battery and use an 18 Ah lead acid one instead.

The biggest hurdle to get over in a project like this one is the logic the camera uses to communicate with the battery. For this reason — and for the ease of hitting the right form factor — he scrapped an old battery pack to reuse the logic board and enclosure. His power supply is a free-formed circuit which fits nicely in the allotted space.

The circuit powers up, but only to about 6.4V. This isn’t enough to run the camera, which means this was just an expensive way for [Michael] to practice his soldering. After the jump you can read his recounting of the experience. You’ll also find a few of the build images, and the two hand-drawn schematics he used during development. His Dropbox has the entire collection of images.

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The BatBox: Portable power, polished and professional. Plus smoke!

batBox

About the size of a shoebox and stuffed with a compact battery/inverter combo, the BatBox packs a mean wallop at 480Wh. What else was [Bill Porter] supposed to do with his free time? He’s already mailed out electronic wedding invitations and built custom LED centerpieces for the reception. He and his wife [Mara] then made an appearance in a Sunday roundup tying the knot by soldering a circuit together. Surely the LED Tetris Tie would have been in the ceremony had it existed. This time, though, [Bill’s] scrounged up some leftover electronics to put a realistic spin on a Minecraft favorite: the BatBox.

A pair of 18V high energy density batteries connect up to a 12V regulator, stepping them down to drive a 110VAC inverter. The BatBox also supplies 5V USB and 12VDC output for portable devices. Unfortunately, [Bill]’s first inverter turned out to be a low-quality, voltage-spiking traitor; it managed to let the smoke out of his fish tank’s LED bar by roasting the power supply. Undeterred, [Bill] pressed on with a new, higher-quality inverter that sits on an acrylic shelf above the batteries. OpenBeam aluminum extrusion seals up the remainder of the enclosure, completing the BatBox with a frame that looks both appealing and durable.

Hack VersaPak battery modules to reuse laptop cells

retrofit-battery-packs-with-laptop-cells

If you’re familiar with VersaPak tools you’ll note that while the battery pack in this image looks somewhat familiar, it’s not supposed to have a removable cell. This is [Martin Melchior’s] hack to use laptop 18650 Lithium cells with VersaPak tools.

The original NiCad packs used three cells for a total of 3.6V, so it is possible to substitute a Lithium cell in the same voltage neighorhood. The tools are pretty hard on the battery packs, drawing a lot of current in certain situations. But these cells are being harvested from dead laptop battery packs so it’s not a huge concern if their life is a bit shortened.

The hack places an 18650 battery receptacle inside of the VersaPak battery housing. There’s a bit of careful disassembly to get to this point, but it’s well illustrated in [Martin’s] project log. And of course you’ll need to use a proper Lithium battery charger from here on out.

This form factor has been popping up in a lot of hacks lately. Here’s another one that modifies the Goal Zero Bolt flashlight to use them.

DIY 23mph+ electric skateboard

What’s the best way to get around NYC? If you asked [papo2110], he would probably suggest you build your own high-speed, long-range electric skateboard. You can’t cruise through any online maker community without tripping over a dozen e-vehicle projects these days. Nearly 18 months ago, even before the popular Boosted Boards Kickstarter, [papo2110] started piecing together a deck. His boards use a brushless outrunner motor, an RC car ESC (complete with brakes), and a chain drive to power him around Central Park at a top speed of 23mph.

The most impressive feat for this project, however, is the tireless revision through iterative design. The deck gets both an aluminum and a carbon fiber upgrade. Meaty 8S Headway LiFePo4’s replace a smaller 6S configuration. Even lights are added. As the build progresses, the board is pushing 27mph: with only one motor. Grab your helmet and motion-sickness pills and strap in for some videos after the break.

If four wheels are one too many and you want even more dangerous speeds, check out the E-trike build from a few months ago.

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I keep my tunes in an ammo can

ammo-can-boombox

Calling this a boom box is at least slightly ironic. Instead of high explosives it now carries high decibels in its new life as a self-contained sound system.

Despite the conspicuous power cord a peek inside reveals a big enough battery to keep the tunes playing for hours on end. [King Rootintootin] kept the cost on the build down since he was given the used speakers and amp by his girlfriend’s dad. The amp kicks out about 25 Watts with the battery rated at 7.2 Ah. He added a charger and routed the controls to the side of the ammo box so that it can be charged without removal. The only external component is the audio jack which connects it to the music source.

One of the suggested improvements from the Reddit thread is to add baffles inside of the enclosure so that sound from the two stereo channels doesn’t interfere with each other.