While browsing through his local dollar store, [Taylor] came across a suspicious looking rock that, upon closer inspection, turned out to be a solar garden light. He scooped it up, took it home and cracked it open, modding it to function as a handheld solar flashlight.
Inside was a pathetically small 40mAh rechargeable battery, which he upgraded to a more standard rechargeable AA. The garden rock came pre-built with its own boost converter to kick up the voltage for the LED, but it was fairly dim. We’re guessing [Taylor] didn’t bother reverse engineering the converter and instead simply did some trial and error, but he managed to increase the LED’s brightness by slapping on a different value inductor.
As fun as it may be to have a rock for a flashlight, [Taylor] decided to cobble together a custom case out of a spare USB charger, making a battery holder and adding a pushbutton. The result is a handy solar flashlight that takes around five hours to charge. Check out some other custom lights: a lithium-powered PVC flashlight or one with a snazzier aluminum body and interchangeable heads.
It may not be particularly useful to create some makeshift batteries out of soda and soda cans, but it’s a good introduction to electrodes and electrolytes as well as a welcomed break from lemons and potatoes. The gang at [Go-Repairs] lopped off the can’s lid and temporarily set the soda aside, then took steel wool to the interior of the can to remove the protective plastic coating. The process can be accelerated by grabbing your drill and cramming the steel wool onto the end of a spade bit, although pressing too hard might rip through the can.
With the soda poured back in, you can eek out some voltage by clipping one lead to the can and another to a copper coin that’s dunked into the soda. Stringing along additional cans in series can scale up the juice, but you’ll need a whole six pack before you can get an LED working—and only just. The instructions suggest swapping out the soda for a different electrolyte: drain cleaner, which can pump out an impressive 12 volts from a six pack series. You’ll want to be careful, however, as it’s likely to eat through the can and is one lid away from being dangerous.
Stick around for a quick video after the break, and if you prefer the Instructables format, the [Go-Repairs] folks have kindly reproduced the instructions there.
Continue reading “DIY soda can battery”
Cordless power tool battery replacements are expensive: you can easily spend $100 for a NiCd pack. [henal] decided to skip nickle-based cells and cut out the middleman by converting his old cordless battery packs to inexpensive hobby lithium cells. These batteries appear to be Turnigy 3S 1300mAh’s from Hobbyking, which for around $10 is a great bargain. As we’ve explained before, lithium batteries offer several advantages over NiMH and NiCd cells, but such a high energy density has drawbacks that should be feared and respected, despite some dismissive commenters. Please educate yourself if you’ve never worked with lithium cells.
[henal] gutted his dead battery packs and then proceeded to prepare the lithium replacements by soldering them to the cordless pack’s power connectors. To keep charging simple, he also branched off a deans connector from power and ground. After cutting some holes in the pack for access to the balancing connector and deans connector, [helan] went the extra mile by soldering on a DIN connector to the balancing wires, which he then securely glued to the side of the case.
We’ve featured lithium power tool replacements before, and these Turnigy packs pose the same problem: they don’t appear to have any low voltage cut-off protection. Check out some of the comments for a good solution.
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.
Continue reading “ContactKey: A portable, battery-powered phonebook”
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.
Continue reading “Graffiti briefcase for stealth tagging”
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.
Continue reading “Fail of the Week: Switched-mode PSU camera battery replacement”
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.