Tool Hacks

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Hackaday Prize 2023: This Differential Scope Probe Is Smarter Than It Looks

September 28, 2023 by 11 Comments

A differential probe, a device for measuring the voltage between two points in a circuit rather than the voltage between a point and ground, it an extremely useful addition to any electronics bench. Inside such a probe you’ll usually find a fancy op-amp working as a differential amplifier, and for correct operation they require careful adjustment to null out DC bias and achieve the maximum common mode rejection. We particularly like [Craig D]’s probe, because these adjustments are taken care of automatically by a microcontroller.

The analogue path provides a lesson for anyone interested in instrumentation signal path design, with the signal conditioning and compensation circuits feeding an AD8130 differential amplifier. Another amplifier samples the output voltage and feeds it to the ADC in the microcontroller. Common mode adjustment is taken care of by a digital potentiometer chip, and DC offset by the microcontroller’s DAC. Controlling all this is an ATSAMD10 chip, and the power is derived from the scope’s USB interface.

All in all it’s an extremely well-executed device, and one we’d be happy to have on our bench at any time. It’s by no means the first differential probe we’ve brought you, here’s another.

 

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Feed Your Fasteners In Line, With A Bowl Feeder

September 26, 2023 by 30 Comments

If you spend much time around industrial processes, you may have seen a vibrating bowl feeder at work. It’s a clever but simple machine that takes an unruly pile of screws or nuts and bolts, and delivers them in a line the correct way up. They do this by shaking the pile of fasteners in a specific way — a spiral motion which encourages them to work to the edge of the pile and align themselves on a spiral track which leads to a dispenser. It’s a machine [Fraens] has made from 3D printed parts, and as he explains in the video below the break, there’s more to this than meets the eye.

The basic form of the machine has a weighted base and an upper bowl on three angled springs. Between the two is an electromagnet, which provides the force for the vibration. The electromagnet needed to be driven with a sine wave which he makes with an Arduino and delivers as PWM via an H-bridge, but the meat of this project comes in balancing the force and frequency with the stiffness of the springs. He shows us the enormous pile of test prints made before the final result was achieved, and it’s a testament to the amount of work put into this project. The final sequence of a variety of objects making the march round the spiral is pure theatre, but we can see his evident satisfaction in a job well done.

Oddly this isn’t the first bowl feeder we’ve seen, though it may be one of the most accomplished. We particularly like this tiny example for SMD parts.

Continue reading “Feed Your Fasteners In Line, With A Bowl Feeder” →

Hackaday Prize 2023: Abuse A Reference Chip For A Cheap Instrument

September 25, 2023 by 11 Comments

A Rogowski coil is a device for measuring AC current that differs from a conventional current transformer in that it has no need to encircle the conductor whose current it measures. They’re by no means cheap though, so over time we’ve seen some interesting variations on making one without the pain in the wallet. We particularly like [Stephen]’s one, because he eschews exotic devices for an interesting hack on a familiar chip. He’s taken the venerable TL431 voltage reference chip and turned it into an op-amp.

We had to look at the TL431 data sheet for this one and shamefacedly admit that since we’d only ever used the chip as a voltage reference, we hadn’t appreciated this capability. In this mode, it’s a op-amp with the inverting input connected to a fixed rail, so it can accept a feedback network to its non-inverting input just like any other. He’s using it as both integrator and amplifier, as well as, of course, in a more conventional power supply.

We like the instrument, and the use of the TL431 in an unexpected manner is the cherry on the cake. Here’s a previous Rogowski circuit using more conventional parts. You can dive a bit more into the theory, too.

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Saving A Scope From The Dumpster

September 24, 2023 by 9 Comments

If you read Hackaday, you probably get the title of [SunEstra’s] post: A Casual Date with the Dumpster. Many great hacking projects start with finding one man’s trash. This June, [SunEstra] rescued an old Tektronix 2465B oscilloscope, which appeared to be in good shape. Why we never find four-channel 400 MHz scopes in the dumpster is hard to explain, but we are still happy for him, if not a little jealous.

As you might expect, powering up the scope was a disappointment. Relays clicked. Lights flashed. But no display. Adjusting the grid bias on the CRT brought up the display, but it also brought up something else: an error message.

The scope was complaining of “test failure 05-40.” A look through the manual reveals that is “positive level too positive.” Huh. Too much of a good thing, we guess. The test checks the A5 board, so a visual inspection there was the first step.

Unsurprisingly, there were electrolytic capacitors leaking electrolyte. This is, apparently, a well-known problem with this scope. Replacing the electrolytics with some similar tantalum capacitors. In a few cases, the corrosion had eaten pads off the PCB, and some were damaged during the removal. It took a little ingenuity to connect the new parts on the board.

The result? A working scope. Maybe the scope will help repair the next thing that comes out of the dumpster. Sometimes, the best dumpster dives involve intercepting the gear before it hits the dumpster. We keep hoping to run into one of these on the curb (the linked post seems dead, but the video is still there).

Getting Geared Up For Home Powder Coating

September 24, 2023 by 17 Comments

[Blondihacks] wanted to do powder coating for a model train without a lot of special equipment. She started with an Eastwood kit that runs about $230. Depending on the options, you can get the gun by itself for between $110 – $170. However, you will need more than just this kit. You can see how [Blondihacks] used the kit in the video below.

The idea behind powder coating is simple: an electrostatic charge attracts a powder — usually some polymer — and makes it stick to an item. Then heat or UV light turns the powder into a hard finish much tougher than paint. Powder coating can be thicker than paint and doesn’t run, either.

The gun requires a small air compressor, and you need an electric oven, which could be a toaster oven. It probably shouldn’t be an oven you plan to use for food. It should also be in a well-ventilated area, plus you’ll want a respirator or dust mask. [Blondhacks] used a portable paint booth so as not to spew powder everywhere, which looked nice, although you could just use a big cardboard box. A custom jig to hang the parts while spraying, and she was ready to go.

If you are on a budget, by the way, you can get a kit from Harbor Freight for a bit less. It probably has fewer accessories, and we don’t know how it compares, but it is an option for much less money. Either way, you need a small air pressure regulator, and you also need a dryer and a filter for the air because you need dry and clean air so as not to contaminate the powder.

The part is grounded, and the gun charges the powder as it sprays. Once coated, you stick the part in the oven for about 20 minutes. The results look good and, compared to a painted part, the coating was super tough. For intricate parts, you can heat the part and then dip it in fluid-like powder. If you prefer to stick to regular powder coating, we have some tips.

Continue reading “Getting Geared Up For Home Powder Coating” →

Two men in black shirts stand between a white and a blue exercise bike sitting on a table in front of them. The exercise bikes have black drums slightly larger than a coffee can affixed to the front of the bike which houses the shredding mechanism. In the background is a "Precious Plastics Torino" circular logo.

Getting Shredded Plastic…and Legs

September 23, 2023 by 10 Comments

While electric motors have taken the drudgery out of many tasks, human power has its advantages. [Precious Plastic Torino] has developed a human-powered plastic shredder for those times when an electric motor just won’t do.

Designed primarily for educational purposes at venues where electricity can be difficult to source, but also useful for off-grid environments, this exercise bike-based shredder can take small pieces of plastic and shred them into tiny pieces suitable for use with any of the other machines in the Precious Plastics ecosystem like their injection molding machine. As with all [Precious Plastics] projects, the files are will be open source; however, there is a six month exclusivity period for Patreon subscribers to help fund development efforts.

The build is relatively simple: take an old exercise bike, remove the unnecessary bits, and run the chain up to drive a shredding mechanism mounted on the front of the bike. We think they should’ve kept the flywheel to help keep the momentum going while shredding but can’t fault them for wanting to keep the prototype as simple as possible. Maybe the next step is getting these in spin classes around the country so people can get their exercise and help recycle in their community at the same time!

If this shredder doesn’t suit your fancy, maybe recycle your plastic with SHREDII or this other DIY effort. If you’d rather generate electricity on your exercise bike, then try building this bike generator.

Continue reading “Getting Shredded Plastic…and Legs” →

DIY Repair Brings An X-Ray Microscope Back Into Focus

September 22, 2023 by 6 Comments

Aside from idle curiosity, very few of us need to see inside chips and components to diagnose a circuit. But reverse engineering is another story; being able to see what lies beneath the inscrutable epoxy blobs that protect the silicon within is a vital capability, one that might justify the expense involved in procuring an X-ray imager.  But what’s to be done when such an exotic and expensive — not to mention potentially deadly — machine breaks down? Obviously, you fix it yourself!

To be fair, [Shahriar]’s Faxitron MX-20 digital X-ray microscope was only a little wonky. It still generally worked, but just took a while to snap into the kind of sharp focus that he needs to really delve into the guts of a chip. This one problem was more than enough to justify tearing into the machine, but not without first reviewing the essentials of X-ray production — a subject that we’ve given a detailed look, too — to better understand the potential hazards of a DIY repair.

With that out of the way and with the machine completely powered down, [Shahriar] got down to the repair. The engineering of the instrument is pretty impressive, as it should be for something dealing with high voltage, heavy thermal loads, and ionizing radiation. The power supply board was an obvious place to start, since electrostatically focusing an X-ray beam depends on controlling the high voltage on the cathode cup. After confirming the high-voltage module was still working, [Shahriar] homed in on a potential culprit — a DIP reed relay.

Replacing that did the trick, enough so that he was able to image the bad component with the X-ray imager. The images are amazing; you can clearly see the dual magnetic reed switches, and the focus is so sharp you can make out the wire of the coil. There are a couple of other X-ray treats, so make sure you check them out in the video below.

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