Repairing And Upgrading A HP 16533A Scope Card

May 10, 2019 by Lewin Day 17 Comments

In the world of oscilloscopes, as in the rest of the test equipment world, there’s always some trickery afoot. Companies will often offer different models to the market at different price points, in an effort to gain the widest possible customer base while also making the most profit. Cheaper, less capable models are often largely identical to more expensive hardware, save for some software or a couple jumpers that disable functionality. [Alexandre] found just this when working to repair his HP 16533A scope card.

Work began when [Alexandre] received his HP 16533A in the mail after a long wait, only to find the trigger functionality was inoperable. This is crucial on a digital scope, so this simply wouldn’t do. After some research online, a post was found discussing which signals to probe to troubleshoot the issue. It noted that corrosion is a common problem on these units, and that occasionally, a certain resistor goes open circuit and causes problems. Initial measurement showed there was still resistance there, but reading closer, [Alexandre] noted this fateful line:

You might not be able to measure it accurately in circuit.

Removing the 100K resistor from the board, the part was indeed open circuit. After replacement with a new component, the trigger circuit was again fully operational. With the scope still open, it was then a simple job to execute a further resistor swap which gives the 16533A the functionality and range of the higher-spec 16534A model.

It’s very common for oscilloscopes and other test hardware to be configured this way from the factory. Rigol scopes are particularly popular with hackers for this very reason.

[Thanks to jafinch78 for the tip!]

Big, Slow Rotary Machine Has Multiple Uses

May 10, 2019 by Lewin Day 14 Comments

A good majority of power tools in the average workshop are all about speed. Drills, grinders, and sanders all whizz along at thousands of revolutions per minute. Sometimes though, you need to do things slowly. For that, [bongodrummer]’s big rotary machine build might be just up your alley.

The core of the build is an old washing machine, which supplies both the machine frame and its powerful universal motor. While this can be hooked directly to a power source and allowed to spin away, it’s far more useful with some speed control in place. For this, an Arduino is hooked up to a triac circuit with feedback, allowing the speed to be set just so for whatever operation you have in mind. A set of speed-reducing pulleys helps further for getting down into the double-digit RPM while maintaining smooth rotation. There’s even a timer for extended operation, with parts salvaged from an old microwave.

The machine is built with a large rotating platter on top. By placing a clean white screen on top, the platter is great for taking 360 degree photos of objects automatically. This could be of great use in a photogrammetry setup. Alternatively, by fitting a bowl and plough assembly, the machine can be used to mull green sand for casting purposes.

It’s a versatile build that could be used for anything that needs rotation in the vicinity of 50 rpm. You could even play vinyl records on it if you were so inclined. Of course, if you’ve built a record player out of an old washing machine, we’d certainly like to know about it.

3D Printed Parts Let You Hold Work The Way You Want

May 5, 2019 by Dan Maloney 6 Comments

Fixturing and work holding can be huge problems for hackers. Let’s face it – that $5, alligator clip-festooned “Helping Hand” is good for only the smallest of workpieces, and the problem only gets worse as the size scales up. One can jury rig fixtures for things like microscopes and lights, but a systematic approach like this 3D-Printed work fixturing Erector Set really appeals to our need for organization.

As [Tinkers Projects] explains it, the genesis of this project came from a need to mount a microscope firmly over a PCB. Rather than build a one-off fixture, the idea of a complete system of clamps and connectors seemed to make more sense. Based on 10-mm aluminum rods and a bewildering number of 3D-printed pieces, the set has just about everything needed to fixture pretty much anything. There’s a vertical element that acts as the central support, connectors for putting another rod perpendicular to that, plus neat attachments like a three-fingered clamp for small cylindrical objects and a couple of blocks that act like a stick-vise for PCBs and similar workpieces. And yes, there’s even a fixture with alligator clips. The whole thing seems very well thought out and has a little mad scientist vibe to it, but while some fixtures look as if they came right from the chemistry lab, we’d be cautious about chemical compatibility and use near heat sources.

[Elliot Williams] did a rundown of what people are using for helping hands a couple of years ago which made us covet articulating dial indicator arms for our bench. Still, [Tinkers Projects]’ approach has a lot of appeal and is probably cheaper and more versatile to boot.

How To Build A Small Metal Furnace At Home

May 4, 2019 by Lewin Day 14 Comments

Casting is a great way to make your own custom metal parts. However, casting requires some manner of furnace capable of generating high enough temperatures to melt the metal in question. Few of us have these just lying around, but never fear. It’s possible to build a basic gas-powered furnace at home, with commonly available materials (Youtube link, embedded below).

This furnace is the work of [Ahmed Ghr], and is as simple a build as they come. The idea is to produce a mold in which to cast concrete to create the furnace. A steel bucket is cut up and used as the outside of the mold, with a pipe inserted in the base to act as a feeder for air and gas. A plastic bucket is then inserted within the steel bucket and held in place with spacers, to create the inner combustion cavity. Concrete is poured in and allowed to set. Once finished, the steel bucket is cut away, and a fire is built over the furnace to melt away the plastic inside. Similar techniques are used to produce the lid, and the furnace is completed.

It’s a build that is executed with the most basic of tools, and should serve as a capable furnace for lower melting point metals at the very least. We’ve seen a lot of cement projects lately, as it turns out. Video after the break.

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Play Tetris On A Transistor Tester, Because Why Not?

May 3, 2019 by Bryan Cockfield 4 Comments

[Robson] had been using the same multimeter since he was 15. It wasn’t a typical multimeter, either. He had programmed it to also play the Google Chrome jumping dinosaur game, and also used it as a badge at various conferences. But with all that abuse, the ribbon cable broke and he set about on other projects. Like this transistor tester that was just asking to have Tetris programmed onto its tiny screen.

The transistor tester is a GM328A made for various transistor testing applications, but is also an LCR meter. [Robson]’s old meter didn’t even test for capacitance but he was able to get many years of use out of that one, so this device should serve him even better. Once it was delivered he set about adding more features, namely Tetris. It’s based on an ATmega chip, which quite easy to work with (it’s the same chip as you’ll find in the Arduino Uno but [Robson’s] gone the Makefile route instead of spinning up that IDE). Not only did he add more features, but he also found a mistake in the frequency counter circuitry that he fixed on his own through the course of the project.

If you’ve always thought that the lack of games on your multimeter was a total deal breaker, this project is worth a read. Even if you just have a random device lying around that happens to be based on an ATmega chip of some sort, this is a good primer of getting that device to do other things as well. This situation is a fairly common one to be in, too.

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Camera Sees Electromagnetic Interference Using An SDR And Machine Vision

April 30, 2019 by Dan Maloney 10 Comments

It’s one thing to know that your device is leaking electromagnetic interference (EMI), but if you really want to solve the problem, it might be helpful to know where the emissions are coming from. This heat-mapping EMI probe will answer that question, with style. It uses a webcam to record an EMI probe and the overlay a heat map of the interference on the image itself.

Regular readers will note that the hardware end of [Charles Grassin]’s EMI mapper bears a strong resemblance to the EMC probe made from semi-rigid coax we featured recently. Built as a cheap DIY substitute for an expensive off-the-shelf probe set for electromagnetic testing, the probe was super simple: just a semi-rigid coax jumper with one SMA plug lopped off and the raw end looped back and soldered. Connected to an SDR dongle, the probe proved useful for tracking down noisy circuits.

[Charles]’ project takes that a step further by adding a camera that looks down upon the device under test. OpenCV is used to track the probe, which is moved over the DUT manually with the help of an augmented reality display that helps track coverage, with a Python script recording its position and the RF power measurements. The video below shows the capture process and what the data looks like when reassembled as an overlay on top of the device.

Even if EMC testing isn’t your thing, this one seems like a lot of fun for the curious. [Charles] has kindly made the sources available on GitHub, so this is a great project to just knock out quickly and start mapping.

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A Stylish Low Part Count Non-Contact Thermometer

April 30, 2019 by Tom Nardi 15 Comments

A non-contact thermometer is a pretty common tool these days, and one that most of us probably have kicking around the lab. You can grab them online for as little as $10 USD, and while they’re nowhere near as capable as a thermal camera, they certainly have their uses. But even with their increased availability, there are at least two safe assumptions we can make about owners of said gadgets: they didn’t make it themselves, and they are probably pretty ambivalent about its aesthetics.

Which makes this project by [Ijon Tichy] particularly interesting. Not only is this a non-contact infrared thermometer that’s extremely easy to build should you be so inclined, but it’s actually quite attractive. In fact, if it wasn’t for the video of it in operation after the break, we would have assumed it was some kind of faux-retro cosplay prop. Even if you don’t have any use for an IR thermometer, you might just want to add one of these to your toolbox on principle.

The main components of the thermometer are a MLX90614 sensor, a gorgeous HP QDSP-6040 bubble display, and a ATtiny2313 microcontroller to tie it all together. The rest are passive components, with the exception of the TP4056 charging module that got tacked on to handle the 200 mAh lithium-ion battery. All of the components are arranged neatly in a line down the length of the thermometer, which is assembled on a piece of perfboard. Rather than go with a 3D printed enclosure that would cover it all up, [Ijon] decided to encapsulate everything in a clear epoxy resin. It looks fantastic, though you’re going to want to triple check all those solder joints before pouring on your “enclosure”.

[Ijon] has provided the diagrams and source code you need to build your own version of this artisanal thermometer, but we think with a custom PCB and perhaps a less liquid enclosure that still shows off the goods, this could be a very popular gadget for the discerning hacker. As we’ve seen, even the most basic of tools can benefit from a stylish makeover.

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