Misc Hacks

4181 Articles

Flexible, Sensitive Sensors From Silly Putty And Graphene

December 18, 2016 by 16 Comments

Everyone’s favorite viscoelastic non-Newtonian fluid has a new use, besides bouncing, stretching, and getting caught in your kid’s hair. Yes, it’s Silly Putty, and when mixed with graphene it turns out to make a dandy force sensor.

To be clear, [Jonathan Coleman] and his colleagues at Trinity College in Dublin aren’t buying the familiar plastic eggs from the local toy store for their experiments. They’re making they’re own silicone polymers, but their methods (listed in this paywalled article from the journal Science) are actually easy to replicate. They just mix silicone oil, or polydimethylsiloxane (PDMS), with boric acid, and apply a little heat. The boron compound cross-links the PDMS and makes a substance very similar to the bouncy putty. The lab also synthesizes its own graphene by sonicating graphite in a solvent and isolating the graphene with centrifugation and filtration; that might be a little hard for the home gamer to accomplish, but we’ve covered a DIY synthesis before, so it should be possible.

With the raw materials in hand, it’s a simple matter of mixing and kneading, and you’ve got a flexible, stretchable sensor. [Coleman] et al report using sensors fashioned from the mixture to detect the pulse in the carotid artery and even watch the footsteps of a spider. It looks like fun stuff to play with, and we can see tons of applications for flexible, inert strain sensors like these.

Continue reading “Flexible, Sensitive Sensors From Silly Putty And Graphene” →

The Engines Of Ingenuity

December 17, 2016 by 10 Comments

Every once in a while, we stumble on an amazing resource that’s not exactly new, but it’s new to us. This is the case, in spades, with The Engines of Our Ingenuity, a radio show that’s been running since 1988!

Each episode covers an invention or engineering marvel, and tells the story of how it came to be, and puts each device into its historical and cultural context. Want to get the lowdown on how we safely bring fire into the kitchen? Or the largest land transport vehicle, NASA’s crawler? And what’s up with lobsters anyway?

Continue reading “The Engines Of Ingenuity” →

Cheap Chainsaw Teardown Reveals Buried Treasures

December 17, 2016 by 102 Comments

People seem to have a love-hate relationship with Harbor Freight, and it mostly seems that they love to hate the purveyor of discount tools. This is not without cause — any number of HF tools have fallen apart in our hands. But there are some gems to be found amid the dregs and dross of your local branch of the 700-store US chain, as long as you match the tool to your needs and manage your expectations.

Now, we’d normally shy away from any electric chainsaw, especially a cordless saw, and doubly so a Harbor Freight special. But as [Professor Charles] demonstrates with his detailed and humorous teardown, the Lynxx 40-volt cordless 14″ chainsaw might be worth picking up just for harvesting parts. First there’s the battery pack, which is chock full of 18650 lithium cells. [Professor Charles] leads us on a detailed tour of the design compromises of the battery and charger and is none too impressed with either, but he clearly understands what it means to build to a price point. While [Charles] found the stock motor controller somewhat anemic, the real buried treasure in the tool is a huge brushless motor, powerful enough to “throw an 8-inch Vise Grip at you” during a (not so) locked rotor test.

The whole teardown is enlightening as to the engineering decisions that go into mass-market tools, so even if you can’t think of something to do with this motor, the article is worth a read. At $169 for the Lynxx (before the 20% coupon in your Sunday paper every week) it’s a little pricey to buy just to harvest parts, but it wouldn’t be the first HF tool to suffer that fate. We’ll bet these things will start showing up broken on the secondary market for a song, and if the [Professor]’s assessments are right, it likely won’t be the motors that fail.

Massive 20-oz. Copper PCB Enables Electric Racing

December 16, 2016 by 49 Comments

Is twenty times the copper twenty times as much fun to work with? Ask [limpkin] and follow along as he fabricates a DC/DC block for a Formula E race car on 20-oz copper PCBs.

The typical boards you order from OSH Park and the like usually come with 1-ounce copper – that’s one ounce of copper cladding per square foot of board. For those averse to Imperial units, that’s a copper layer 34 micrometers thick. [limpkin]’s Formula E control board needs to carry a lot of current, so he specified 700-micrometer thick cladding, or 20-oz per square foot. The board pictured cost $2250, so you’d figure soldering on the components would be an exotic process, but aside from preheating the board, [limpkin] took it in stride. Check out the image gallery of the session and you’ll see nothing but a couple of regular high-wattage soldering irons, with dirty tips to boot.

It’s pretty neat comparing what’s needed for power electronics versus the normal small signal stuff we usually see. We’d recommend looking at [Brian Benchoff]’s “Creating a PCB in Everything” series for design tips, but we’re not sure traditional tools will work for boards like these. And just for fun, check out the Formula E highlights video below the break to see what this build is part of.

Continue reading “Massive 20-oz. Copper PCB Enables Electric Racing” →

[Huan] Liberates A Router

December 16, 2016 by 32 Comments

[Huan Truong] was given a WiFi router and thought he’d improve it by installing a free firmware on it. Unfortunately, the router in question is a bit old, and wasn’t ever popular to begin with, which meant that it was unsupported by the usual open firmware suspects. The problem was that it only had a 4 MB flash to boot off of, but [Huan] was determined to make it work. (Spoiler: he did it, and documented it fully.)

The flash workaround consisted basically of repartitioning the space, and then telling u-boot where to find everything. On a router like the WNR2000 that [Huan] had, the flash is memory-mapped, which meant adding an offset to the flash start (0xbf000000 instead of 0x00000000) and remembering to do this consistently so that he doesn’t overwrite things like the MAC address.

[Huan] went for the LEDE fork of OpenWRT, and rebuilt it from source because he needed a small version to fit inside his limited flash. With this task completed, it worked. All done? Nope, [Huan] then submitted a pull request to LEDE, and now you can enjoy the fruits of his labor without replicating it. But if you’ve got another low-flash, obscure router, you’ve got a head start in getting LEDE up and running on it.

Routers are perhaps the most-hacked device that we see here, and they can be made pretty darn useful with the right firmware. Sometimes getting a custom firmware running is relatively easy, as it was here, and sometimes it requires some deep reverse engineering. But it’s good to keep up your router-hacking chops, because they may not always be as open as they are now.

Build This Barn Door Tracker Today, Take Stunning Shots Of The Galaxy Tonight

December 15, 2016 by 18 Comments

Think you need some fancy equipment to get stunning shots of the night sky? Surely those long-exposure shots that show the Milky Way in all its glory take expensive telescopes with complicated motor-driven equatorial mounts, right? Guess again – you can slap together this simple barn door tracker for a DSLR for a couple of bucks and by wowing people with your astrophotography prowess tonight.

Those stunning, deeply saturated shots of our galaxy require a way to cancel out the Earth’s movement, lest star trails ruin your long exposure shots. Enter the barn door tracker, a simple device to let you counter the Earth’s rotation. [benrules2]’s version of the tool is ridiculously simple – two boards connected by a hinge. A short length of threaded rod with a large handle passes through a captive nut in the upper board.

A little trig allows you to calculate how much and how often to turn the handle (by hand!) to counter the planet’s 0.25°/minute diurnal rotation. Surprisingly, the long exposure times seem to even out any jostling introduced by handling the rig, but we’d still imagine a light touch and a sturdy tripod would be best. Those of you with less patience might automate this procedure.

It seems a lot to ask of a rig that you could probably throw together in an hour from scrap, but you can’t argue with [benrules2]’s results. His isn’t the only barn door tracker we’ve covered, but it looks like the simplest by far and would be a great project to build with kids.

[via r/DIY]

Measuring Spurious Emissions Of Cheap Handheld Transceivers

December 14, 2016 by 43 Comments

If you buy an amateur transceiver cheap enough to make a reasonable grab bag gift or stocking stuffer, you get what you pay for. And if this extensive analysis of cheap radios is any indication, you get a little more than you pay for in the spurious emissions department.

Amateur radio in the United States is regulated by the FCC’s Part 97 rules with special attention given to transmitter technical specifications in Subpart D. Spurious emissions need to be well below the mean power of the fundamental frequency of the transmitter, and [Megas3300] suspected that the readily available Baofeng UV-5RA dual-band transceiver was a little off spec. He put the $20 radio through a battery of tests using equipment that easily cost two orders of magnitude more than the test subject. Power output was verified with a wattmeter, proper attenuators were selected, and the output signal scanned with a spectrum analyzer. Careful measurements showed that some or all of the Baofeng’s harmonics were well above the FCC limits. [Megas3300] tested a few other radios that turned out to be mostly compliant, but however it all turned out, the test procedure is well documented and informative, and well worth a look.

The intended market for these radios is more the unlicensed crowd than the compliant ham, so it’s not surprising that they’d be out of spec. A ham might want to bring these rigs back into compliance with a low pass filter, for which purpose the RF Biscuit might prove useful.

[via r/AmateurRadio]