Upgrading Cordless Drill Batteries to Lithium


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.

Musical Pencil Synthesizer


Here’s another fun weekend project for the hacker younglings, a musical synthesizer that plays different musical tones based on the resistance of your conductive graphite drawing!

Like our recent post on a DIY Metal Detector, this project makes use of the ever relevant 555 timer. Except in this case they are using a more modern TLC555 timer which only requires 3V instead of the typical 4.5V. It’s a fairly simple project that you should be able to complete in just a few hours.

The circuit is quite basic. The 555 timer outputs in astable mode, which means there is a continuous stream of pulses from pin 3 which go right into the speaker circuit. The rest of the circuit monitors the resistance of whatever the pencil is touching, including you! Changes in resistance result in the variation of pulses outputted by the 555 timer.

As always, the video guide is after the break.

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Electronics Everything Reference Poster


[Ben] just sent us this great reference sheet. It’s a poster he compiled of datasheets and various electronic references. He made it after spending too much of his time sifting through datasheets while working on projects. It also helped that he realized his school, Georgia Tech, had a poster printing service!

It contains the basics from resistor color codes, typical pinouts of various chips, current capacity of wire gauges, Arduino pinout diagrams, schematic symbols, trace widths for current capacity, and even typical coding functions!

The full image is 9,000 x 6,000 pixels and will print nicely at 30 by 20 inches, just shy of the ANSI D paper size. It’s 6.1MB so only click here if you want it!

Maybe if we ask nicely he’ll share the original MS Publisher file so we can tailor it to our individual needs! Some of the text in the images is a bit blurry, but everything is basically still readable.

Headphone Hack Makes Wireless an Option


If you have a favorite pair of over-the-ear headphones you may want to consider upgrading them with a wireless option. The key word here is “option” because these still retain their functionality as a wired headphone. This is nice if you only want to deal with battery life when you’re actually roaming around.

Of course the thing that makes this type of hack work is the extra room inside the body of the earpieces. [Tony] cracked them open and decided there was just enough room to fit the internals of a Bluetooth audio adapter. It has it’s own Li-ion battery (boasting 12 hours of use) which is why there is an added charging port. To fit the board he had to remove some of the aluminum body from the enclosed part of the headphones. He also wired up a tactile switch to act as the power button for the Bluetooth module.

Details are scarce on how the speakers are wired between the module and the jack. But we think he simply wired them in parallel rather than using a switched jack. You can see a quick demo after the break but it really doesn’t augment the build details at all.

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Touring Component Markets in Shenzhen


[Al] recently returned from a trip to China. While there he toured some of the component markets in Shenzhen, the electronics assembly epicenter of the world. While he doesn’t focus too closely on what is actually being sold there, we found his description of the markets themselves and other notable attractions around the area quite interesting.

Shenzhen is different from some of the other component wonderlands we’ve heard about ([Ian Lesnet's] tour of Akihabara in Japan comes to mind). First of all it may be a bit more difficult to get there. US Citizens need a Visa to enter China, and must fly to Hong Kong and take a ferry to the mainland. [Al] reports that the traffic is horrendous and rush-hour can turn a ten mile ride that usually takes ninety minutes into a three hour tour… a three hour tour!

The side affect of the market being out of the way is that the prices aren’t as inflated as they may be in more geek-tourist-friendly locations. That being said it also sounds like the vendors are interested in selling you a few thousand units rather than a single component. Follow the link at the top for the market tour, a stop at Seeed Studios (who will apparently sell you a map of the best markets to visit), and the rest of the attractions that [Al] encountered.

Breadboard Tetris is Wire Artwork


Look closely at the colored pixels on this pair of 8×8 RGB LED modules and you’ll be able to pick out some of the familiar shapes of Tetris pieces. It’s impressive that [Jianan Li] built his own color Tetris including the theme music, but look at this breadboard! The layout of his circuit is as equally impressive as the code he wrote to get the game up and running. It takes a fair amount of planning to get a circuit of this complexity to fit in the space he used, right?

There are two microcontrollers at work, each running the Arduino bootloader. The main chip is an ATmega328 which is responsible for monitoring the buttons and controlling game play. The other is an ATmega85. The eight pin chip listens to it’s bigger brother, playing the theme song when the game starts, and pausing or resuming to match the user input So is the next stop for this project playing Tetris on the side of a building?

Don’t miss the demo video after the break. We’ve also rolled in a video of his Arduino-based piano. It’s built on a breadboard that’s nearly as impressive as this. But what delights us is his skill at playing Pokemon themes on the two-octave tactile switch keyboard. Obviously those piano lessons his parents shelled out for really paid off!

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Custom E-Cruiser has features for disabled rider


As [AussieJester] noted in the first page of his build log, most people’s idea of a “custom-made” electric bicycle involves strapping some electronics and a hub motor onto any off-the-shelf bike. He needed a bigger challenge, so he fabricated his own frame to build a stylish electric cruiser. This bike has a 2-speed transmission and a massive Turnigy 80-100 brushless outrunner motor, which pushes out a top speed of 45mph.

You may have noticed what look like training wheels in the picture above, and you’d be half-correct. [AussieJester] is a paraplegic, and needed to guarantee some stability both when transferring from his wheelchair and when coming to a stop. The best feature of this bike, however, is that these small wheels are retractable. A linear actuator lowers them for slower speeds and for mounting/dismounting, but picks them back off the ground once you are up to speed, maintaining a true 2-wheeled experience.

Stick around for a couple of videos after the break: a first-person POV showing just how quick this bike can move, and a demonstration of the actuators. Then check out another EV pioneer in the world of skateboarding.

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