Hackaday Links: March 3, 2014

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If you’re playing along with Twitch Plays Pokemon, you might as well do it the right way: with the smallest Game Boy ever, the Game Boy Micro. [Anton] needed a battery replacement for this awesome, discontinued, and still inexplicably expensive console and found one in a rechargeable 9V Lithium battery. You get two replacement cells out of each 9V battery, and a bit more capacity as well.

Every garden needs garden lights, right? What does every garden light need? A robot, of course. These quadruped “Toro-bots” react to passersby by brightening the light or moving out of the way. It’s supposed to be for a garden that takes care of itself, but we’re struggling to figure out how lights will do that.

Flexiable 3D prints are all the rage and now resin 3D printers are joining the fray. The folks at Maker Juice have introduced SubFlex, a flexible UV-curing resin. The usual resins, while very strong, are rock solid. The new SubFlex flexible resins are very bendable in thin sections and in thicker pieces something like hard rubber. We’re thinking custom tank treads.

Remember this post where car thieves were using a mysterious black box to unlock cars? Looks like those black boxes have moved from LA to Chicago, and there’s still no idea how they work.

Have a Google Glass? Can you get us on the list? [Noé] and [Pedro] made a 3D printed Google Glass adapter for those of us with four eyes.

Newsstand Shotgun Hack Poised to Further Ruin Air Travel

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The people who go nuts over 3D printed guns are going to have a field day with this one. It’s a shotgun and ammo built entirely from items you can purchase after passing through airport security. Now look, obviously the type of folks who read Hackaday understand that security in any form is something of an illusion. House keys don’t keep people from breaking into your home. Encryption doesn’t keep the government from looking over your shoulder. And no level of security screening can eliminate every possible hazard. So let’s just enjoy this one for the fine act of hacking that it is.

[Evan Booth] put his mind to work on the items you can buy at the stores inside of an airport terminal. Above you can see the diagram of all the parts. The break action accepts a Red Bull can that acts as the cartridge for the shotgun (our calculations put this at just under 0.25 Gauge). The bottom of the can contains water separated from Lithium metal (from cellular phone accessories?) by a condom. When the nonet of 9V batteries are connected to the heating element from the hair dryer it melts a hole in the prophylactic, mixing the water with the metal causing a reaction that propels pocket change as the projectile. The video after the break shows that this does take a while… perhaps 10 seconds from the time the trigger is pulled. Oh, and you might not want to be holding the thing when it goes off. We’d say the firearm can barely contain the explosion.

If you like this (or were horrified by it) [Evan's] got a whole collection of weapons built inside the airport terminal. For those that care, here’s a link to the most recent of 3D printed gun posts which we referenced earlier.

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Upgrading Cordless Drill Batteries to Lithium

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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.

Hack VersaPak battery modules to reuse laptop cells

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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.

Goal Zero Bolt hack lets your flashlight use non-proprietary batteries

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[Harrson] was really excited to get a deal on this Goal Zero Bolt flashlight. It’s and LED flashlight that uses Lithium batteries that are recharged via USB. That’s really handy. But when he cracked it open, like any good hacker does with new toys, he found that it won’t charge standard 18650 Lithium cells. That’s the form factor it’s using, but the proprietary cell that comes with it has both conductors at the top.

So where did [Harrson] start with the project? He called the company to ask about the setup. They were able to confirm that the proprietary cells just have a conductor which brings the bottom contact of the cell up to the top. We’d bet this is to make the flashlight itself easier to manufacture.

He got to work by scavenging a flat Kapton covered conductor from an old laptop battery. This thin strip is manufactured for connecting the cells of a battery, and it’s quite flat so it will be able to bypass the 18650 cell housing inside of the battery compartment. He made a solder connection for the strip inside the recharging compartment, leaving a tail which makes contact with the base of a standard cell.

If you’ve ever cracked open a dead laptop battery you probably found round Lithium cells. These are most commonly the 18650 variant we’ve been talking about. The battery dies when just one cell goes bad, so [Harrson] has a supplies of the good cells which he’ll be able to substitute into his flashlight as needed.

Make your own electronic children’s toys

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[Miria Grunick's] son nephew is two years old. If you’ve ever looked at that age range in the toy aisle we sure you’ve noticed that there’s a mountain of cheap electronic stuff for sale. Manufactures are cramming LEDs and noise makers into just about all kids stuff these days. But [Miria] thought why not just make him something myself? She calls this the Blinky Box. It’s an acrylic enclosure stuffed with pretty LEDs that is controlled with a few buttons.

It’s driven by a Teensy 3 board which monitors a half dozen colorful buttons, a mode selector on the side, and an on/off switch. The device is powered by a Lithium battery that recharges via USB. And of course there’s a strip of individually addressable RGB LEDs inside.

The demo shows that one mode allows you to press a button color and have the LEDs change to it. But there are other features like fade and scroll. She also mentions that since it can be reprogrammed the toy can grow with hime. Maybe it’ll be a Simon Says game. But eventually she hopes he’ll use it to learn the basics of programming for himself.

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Salvaging Lithium cells and circuits

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Lithium cells outperform Nickel Cadmium and Nickel Metal Hydride in almost every way. But they also need a little bit more babysitting to get the most out of them. That comes in the form of control circuitry that charges them correctly and won’t let them get below a certain voltage threshold during discharge. We enjoyed reading about [Carlos'] Lithium cell salvage efforts as it discusses these concerns.

He wanted to salvage a Lithium power source for his projects. He had the three cell pack from a dead Macbook Pro seen in the upper left, as well as the single blown cell from a digital picture frame shown on the right. The three-pack didn’t monitor each cell individually, so the death of one borked the entire battery. He desoldered them and probed their voltage level to find one that was still usable. To prevent his project from draining the source below the 2.7V mark he scavenged that circuit board from the digital picture frame. A bit of testing and the system is up and running in a different piece of hardware.

Don’t be afraid of this stuff. If you learn the basics it’ll be easy to use these powerful batteries in your projects. For more background check out this charging tutorial.