Building an accurate equal arm balance

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microscale

This interesting take on weights and measures uses a two foot long level as the base for a diy equal arm balance. The balance is the oldest method used for measuring mass. That’s because you don’t even need a reference weight for it to work as long as you are measuring ingredients that are proportional to each other in whole numbers.

The key to accuracy with these scales is to reduce friction at the fulcrum. In this case the fulcrum is made of two upturned razor blades on the base, with a single razor blade resting perpendicular to those on the arm. But because gravity is doing the equalization, the base must be as level as possible. Adjustable feet were added to the base so that it can be leveled on two axes. When the tower at the center was built (using threaded rod) a disc level was used to fine-tune the mounting angle of the two razor blades. The finishing touches include a coupling nut on each end for fine-tuning the balance, and the halves of a tea ball strainer as the weighing vessels.

 

Filed Under: tool hacks Tagged With: , , ,

Toothbrush timer

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This toothbrush holder will make sure you’re brushing your pearly whites for an appropriate length of time. The three cups serves as tootbrush storage, and detect when one has been removed. Once you start brushing your teeth the lights on the front and bell in the back count down the process automatically.

The counting sequence starts when a weight sensor in the base detects a change caused by picking up a toothbrush. The ATmega328 — which is programmed with Arduino-style code — then turns on all of the incandescent lamps mounted on the front portion of the base. Each of these are switched with a 2N3904 transistor in order to sink enough current for the bulb. As a two-minute timer decrements, the bulbs are extinguished one by one. But there is also an auditory feedback mechanism. On the back of the base is a small bell. A hammer on a servo strikes the bell every 30 seconds to let you know how you’re doing. The entire thing is driven by an internal Li-ion battery which lasts about three weeks between charges. Don’t miss the demo video found after the break.

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Filed Under: home hacks Tagged With: , , , , ,

Zigbee-powered wireless scale

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[joe] wanted to make it easy to record his weight every day, and added a few bits to decode the weight and send it to his computer. The end result is a ZigBee-powered wireless scale. Additionally, his scale can track more than one person’s data simply by knowing whose previous weight the new measurement is closest to. Now [joe] and his family can spend more time working out, and less time messing with spreadsheets and data entry.

[joe]‘s build is not only elegant, but well-documented, too. He walks through the reasons he chose this specific floor scale, reverse engineering it to decode the weight, then provides links to his schematics, source code, and pretty much everything else you would need to play along at home.

Filed Under: Medical hacks, Microcontrollers, wireless hacks Tagged With: , , ,

USB ports hidden inside gaming mouse

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[Gigawatts] built a pair of USB ports into his mouse and there’s enough room to plug-in small USB drives and dongles. After seeing Thursday’s storage mouse hack he decided to tip us off about the post.

He started with a Logitech G5 gaming mouse. The wireless version of this mouse has a battery pack, but on the corded version this space is used for a weight cartridge. Since he didn’t really care about that feature he ditched the weights, added a USB hub inside, and positioned the dual ports as seen in the photo. The void is deep enough for the mouse to function normally while hosting medium to small-sized devices. This is a fantastic solution that’s at least as impressive as Apple adding USB ports to a keyboard. We’d love to see it as a factory option.

Update: Video after the break

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Filed Under: peripherals hacks Tagged With: , , , , , ,

iPhone 4 steadicam

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It’s been a while since we’ve seen a steadicam, and to quench our thirst is this  iPhone 4 steadicam. The system does use the typical 3 axis PVC gimbal and heavy weight setup that we’ve seen before, but (why has it taken so long to get this implemented?) the addition of a hand grip means you no longer get blistered fingers. The tutorial recommends the use of an expensive cup holder mounting system, but we think making your own epoxy one might save another dime and allow a wider range of cameras or phones.

The whole process is also wrapped up in a quick and simple how-to video (after the jump alongside an in action video), which goes to show even though a hack may have been done several times before, presentation can make a big difference and impact.

[Thanks Max Lee]

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Filed Under: news Tagged With: , , , , ,

Three pendulum harmonograph

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Just the other day we were thinking “You know what we need more of around here? Harmonographs!” And our requests were answered when [Paul] sent in his three pendulum harmonograph. For those unaware, it’s a mechanical device that draws Lissajous curves or “really cool circles” to quote some of our staff.

[Paul] includes all the plans necessary to make your own harmonograph and begin drawing today. If you can’t wait, there’s a video of the three pendulum harmonograph etching a masterpiece after the jump. [Read more...]

Filed Under: misc hacks Tagged With: , , , , , , ,

DIY coffee table scale

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scale

[Guus] screwed together this coffee table which doubles as a scale. No welding was required to put it together – just some bolts, pulleys, miscellaneous fittings, and an original design. The weight is indicated through the (unlabeled) position of the counterweight arm. Currently it is limited to measuring 10kg (22 pounds), but can easily be boosted by adding a heavier counterweight. It looks pretty robust, maintenance-free, and fitting for any living room workshop’s weighing needs. [Guus] is also the proud inventor of the rock radio, and he is working on creating Man-Y-Man: a modular play system allowing children to create up to 1520 unique creatures.

Filed Under: misc hacks Tagged With: , , , ,
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