Misc Hacks

4179 Articles

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.

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[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]

TP-Link Debug Protocol Gives Up Keys To Kingdom

December 14, 2016 by 25 Comments

If the headline makes today’s hack sound like it was easy, rest assured that it wasn’t. But if you’re interested in embedded device hacking, read on.

[Andres] wanted to install a custom OS firmware on a cheap home router, so he bought a router known to be reflashable only to find that the newer version of the firmware made that difficult. We’ve all been there. But instead of throwing the device in the closet, [Andres] beat it into submission, discovering a bug in the firmware, exploiting it, and writing it up for the manufacturer.  (And just as we’re going to press: posting the code for the downgrade exploit here.)

This is not a weekend hack — this took a professional many hours of serious labor. But it was made a lot easier because TP-Link left a debugging protocol active, listening on the LAN interface, and not requiring authentication. [Andres] found most of the information he needed in patents, and soon had debugging insight into the running device.

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The Many Uses Of The Neon Lamp

December 12, 2016 by 44 Comments

Neon lights are that kind of nostalgic item that everybody seems to love. The neon lamp is a type of gas discharge lamp, they generate light when an electrical discharge travels through an ionized gas, or plasma. When the voltage between the electrodes exceeds certain threshold, the gas ionizes and begins conducting electricity. The basic process that generates light is the return of the ions to the ground energy state, with the emission of a photon of light. The light color depends on the emission spectra of the atoms in the gas, and also  on the gas pressure, among other variables.  Gas discharge lamps can be classified by the pressure of the gas:

  • Low pressure: includes the neon lamp, fluorescent lamps and low pressure sodium lamps.
  • High pressure: such as the metal halide, high pressure sodium and mercury vapor lamps.

Another classification comes from the heating method of the cathode:

  • Hot cathode lamps: the electric arc between the electrodes is created via thermionic emission, where electrons are expelled from the electrodes because of the high temperature.
  • Cold cathode lamps: In these, the electric arc results from the high voltage applied between the electrons, that ionizes the gas and conduction can take place.

High intensity lamps are another type of gas discharge lamp where a high power arc is formed between tungsten electrodes. Power levels of several kilowatts can be easily produced this type of lamp. Of course we can’t forget to mention nixie tubes, which are a type of cold cathode neon lamp, popular for building retro clocks. Fortunately, they are now in production again.

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