Milliohm Meter Version 1.5

A milliohm meter is a very handy piece of test equipment. Most hand-held multimeters cannot measure low resistances and bench meters that can, are usually quite expensive. [barbouri] has shared details of his milliohm meter build on his blog post, and it looks pretty nice.

When using a single pair of leads to measure very low ohms, the resistance of the measuring wires and voltage drops across the various joints become substantial enough to invalidate your measurement. The solution is to use the “Kelvin method” or 4-wire measurement. This involves passing a highly stable current derived from a temperature compensated constant-current source through the unknown resistance, and then using another pair of leads to measure the voltage drop across the resistor, which then gets displayed as a resistance on a voltmeter.

The finished project not only looks good, but is able to measure up to 2Ω with a resolution of 0.0001Ω (that’s 0.1mΩ). The project is originally designed by [Louis] from [Scullcom Hobby Electronics] and [barbouri]’s second iteration adds an improved board layout to the original project.

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3D Printer Transforms to CNC

Superficially, it is easy to think about converting a 3D printer into a CNC machine. After all, they both do essentially the same thing. They move a tool around in three dimensions. Reducing this to practice, however, is a problem. A CNC tool probably weighs more than a typical hotend. In addition, cutting into solid material generates a lot of torque.

[Thomas Sanladerer] knew all this, but wanted to try a conversion anyway. He had a few printers to pick from, and he chose a very sturdy MendelMax 3. He wasn’t sure he’d wind up with a practical machine, but he wanted to do it for the educational value, at least. The result, as you can see in the video below, exceeded his expectations.

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New Lathe Day is Best Day

As [Quinn Dunki] rightly points out, modern industrial civilization was probably conceived on the bed of a lathe. Turning is an essential step in building every machine tool, including lathes, and [Quinn] decided it was time to invite one into her shop. But she discovered a dearth of information to guide the lathe newbie through that first purchase, and thus was born the first installment in her series on choosing and using a new lathe.

As for the specifics of the purchase, [Quinn]’s article goes into some depth on the “old US iron” versus “new Asian manufacture” conundrum. Most of us would love an old South Bend or Cincinnati lathe, but it may raise practical questions about space planning, electrical requirements, and how much work is needed to get the old timer working again. In the end, [Quinn] took the path of least resistance and ordered a new lathe of Chinese heritage. She goes into some detail as to what led to that decision, which should help other first-timers too, and provides a complete account of everything from uncrating to first chips.

Nothing beats the advice of a grizzled vet, but there’s a lot to be learned from someone who’s only a few steps ahead of her intended audience. And once she’s got the lathe squared away, we trust she’ll find our tips for buying a mill helpful getting that next big shipment delivered.

“All the best things in life arrive on a pallet.” Have truer words ever been spoken? Sure, when the UPS truck pulls up with your latest Amazon or eBay treasure, it can be exciting. But a lift-gate truck rolling up to the curb? That’s a good day.

Programming Thousands of AVRs

It is funny how almost everything has its own set of problems. Rich people complain about taxes. Famous people complain about their lack of privacy. It probably won’t happen us, but some Kickstarter campaigners find they are too successful and have to scale up production, fast. We’d love to have any of those problems.

[Limpkin] found himself in just that situation. He had to program several thousand Atmel chips. It is true that you can get them programmed by major distributors, but in this case, he wanted unique serial numbers, cryptographic keys, and other per-chip data programmed in. So he decided to build his own mass programming workbench.

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Cordless Drill Uses no Electricity

There are few projects on how to make your own cordless drill, but what sets [Johnnyq90’s] amazing project apart is the fact that his power plant is a nitro engine. Not an easy task of course, but he makes it look easier than it is, and we really enjoyed the construction process.

He uses an RC Kyosho GX12 engine that was previously modified, changing the cooling head with a larger one. The engine drives a gearbox that was taken from another drill. All other parts were hand made. The clutch was carefully machined, and the cooling fan was made in a 3D printer. Other necessary parts were the frame, brass spacers to adjust the engine height and alignment, throttle arm and handle. In the end even the gearbox had to be modified for higher speed. The finished drill sure looks and sounds terrific, and seems to be perfectly capable of doing its job.

As with other mechanical projects from [Johnnyq90], the video has good timing and attention to detail. His channel is definitely worth a visit, specially if you like turbines.

Heavy Lift Electromagnet from Microwave Oven Transformers

It’s OK, you can admit it — from the time you first saw those huge electromagnetic cranes in scrap yards you’ve wanted to have one. While it may not fling around a car, parts donated from scrapped microwaves can let you build your own electromagnetic lifting device and make that dream finally come true.

We recently watched [MakeItExtreme] turn a couple of microwave oven transformers into a somewhat ill-advised wall-climbing rig. It looks like that may have been the inspiration for this build, and the finished product appears to be a tad more useful this time. The frames of three MOTs are cut open to remove the secondary coils and leave the cores exposed as poles for the future magnets. A shallow dish is fabricated out of steel and the magnets are welded in place.

With the primaries wired together, the magnets are epoxy potted, the business end is faced off cleanly, and the whole thing put to the test. [MakeItExtreme] doesn’t go into control details in the video below, but the website mentions the magnet being powered off a 24V 15A power supply with battery backup in case of mains failure.

They’ve lifted 200kg so far, and it looks like a pretty cool addition to a shop already packed with other builds, like their MOT spot welder and a propane tank sandblaster.

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[Dave’s] Not Just a Member of the Air Club for Tweezers

We are always surprised how much useful hacking gear is in the typical craft store. You just have to think outside the box. Need a hot air gun? Think embossing tool. A soldering iron? Check the stained glass section. Magnification gear? Sewing department.

We’ve figured out that people who deal with beads use lots of fine tools and have great storage boxes. But [Dave] found out they also use vacuum pickup tweezers. He had been shopping for a set and found that one with all the features he wanted (foot pedal, adjustable air flow, and standard tips) would run about $1000.

By picking up a pump used for bead makers and adding some components, he put together a good-looking system for about $200. You can see a video of the device, below, and there are several other videos detailing the construction.

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