How To Reverse Engineer, Featuring The Rigol DS1054Z

October 22, 2014 by Brian Benchoff 50 Comments

For a few years now, the Rigol DS1052E has been the unofficial My First Oscilloscope™. It’s cheap, it’s good enough for most projects, and there have been a number hacks and mods for this very popular scope to give it twice as much bandwidth and other interesting tools. The 1052E is a bit long in the tooth and Rigol has just released the long-awaited update, the DS1054Z. It’s a four-channel scope, has a bigger screen, more bells and whistles, and only costs $50 more than the six-year-old 1052E. Basically, if you’re in the market for a cheap, usable oscilloscope, scratch the ~52E off your list and replace it with the ~54Z.

With four channels of input, [Dave Jones] was wondering how the engineers at Rigol managed to stuff two additional front ends into the scope while still meeting the magic price point of $400. This means it’s time for [Dave] to reverse engineer the 1054Z, and give everyone on the Internet a glimpse at how a real engineer tears apart the worth of other engineers.

The first thing [Dave] does once the board is out of the enclosure is taking a nice, clear, and in-focus picture of both sides of the board. These pictures are edited, turned into a line drawing, and printed out on a transparency sheet. This way, both sides of the board can be viewed at once, allowing for a few dry erase marker to highlight the traces and signals.

Unless your voyage on the sea of reverse engineering takes you to the island of despair and desoldering individual components, you’ll be measuring the values of individual components in circuit. For this, you’ll want a low-voltage ohms function on your meter; if you’re putting too much voltage through a component, you’ll probably turn on some silicon in the circuit, and your measurements will be crap. Luckily, [Dave] shows a way to test if your meter will work for this kind of work; you’ll need another meter.

From there, it’s basically looking at datasheets and drawing a schematic of the circuit; inputs go at the left, outputs at the right, ground is at the bottom, and positive rails are at the top. It’s harder than it sounds – most of [Dave]’s expertise in this area is just pattern recognition. It’s one thing to reverse engineer a circuit through brute force, but knowing the why and how of how the circuit works makes things much easier.

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Function Generator With Zero CPU Cycles

October 22, 2014 by Brian Benchoff 34 Comments

No one is sitting around their workbench trying to come up with the next great oscilloscope or multimeter, but function generators still remain one of the pieces of test equipment anyone – even someone with an Arduino starter pack – can build at home. Most of these function generators aren’t very good; you’re lucky if you can get a sine wave above the audio spectrum. [Bruce Land] had the idea to play around with DMA channels on a PIC32 and ended up with a function generator that uses zero CPU cycles. It’s perfect for a homebrew function generator build, or even a very cool audio synthesizer.

The main obstacles to generating a good sine wave at high frequencies are a high sample rate and an accurate DAC. For homebrew function generators, it’s usually the sample rate that’s terrible; it’s hard pushing bits out a port that fast. By using the DMA channel on a PIC32, [Bruce] can shove arbitrary waveforms out of the chip without using any CPU cycles. By writing a sine wave, or any other wave for that matter, to memory, the PIC32 will just spit them out and leave the CPU to do more important work.

[Bruce] was able to generate a great-looking sine wave up to 200 kHz, and the highest amplitude of the harmonics was about 40db below the fundamental up to 100 kHz. That’s a spectacular sine wave, and the perfect basis for a DIY function generator build.

Take Your Samples For A Spin With The RWXBioFuge

October 21, 2014 by Theodora Fabio 14 Comments

We have a confession to make: we love centrifuges. We’ve used all shapes and sizes, for spinning bags of whole blood into separate components to extracting DNA, and everything in between. Unfortunately, these lab staples are too expensive for many DIY-biologists unless they buy them used or build them themselves. [Pieter van Boheemen] was inspired by other DIY centrifuges and decided to make his own, which he named the RWXBioFuge.

[Pieter] designed the RWXBioFuge using Sketchup, OpenSCAD, and InkScape. It features a Thermaltake SMART M850W ATX power supply, an R/C helicopter Electronic Speed Controller (ESC), and brushless outrunner motor. For user output it utilizes a 16×2 LCD character display with an I2C interface.The frame is laser-cut from 3mm MDF while the 3D-printed PLA rotor was designed with OpenSCAD.

An Arduino handles the processing side of things. [Pieter] used an Arduino Ethernet – allowing a web interface to control the centrifuge’s settings and operation from a distance. We can see this being useful in testing out the centrifuge for any rotor/motor balance issues, especially since [Pieter] states that it can be configured to run >10,000 rpm. We wouldn’t want to be in the room if pieces start flying off any centrifuge at that speed! However, we feel that when everything’s said and done, you should have a centrifuge you can trust by your side when you’re at your lab bench.

While there are similarities to the Openfuge, the larger RWXBioFuge has rotor capacities of eight to twenty 1.5-2.0ml microcentrifuge tubes. Due to the power supply, it is not portable and a bit more expensive, but not incredibly so. There are some small touches about this centrifuge that we really like. The open lid detector is always a welcome safety feature. The “Short” button is very handy for quick 5-10 second spins.

A current version of the RWXBioFuge is being used at the Waag Society’s Open Wetlab. [Pieter’s] planned upgrades for the next version include a magnetic lid lock, different rotor sizes, an accelerometer to detect an improperly balanced rotor, and optimizing the power supply, ESC, and motor setup. You can never have enough centrifuges in a lab, and we are looking forward to seeing this project’s progress!

Check out a few more pictures of the RWXBioFuge after the break.

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Think Before You Measure – Old Test Gear And Why It Is Awesome

October 20, 2014 by Gregory L. Charvat 49 Comments

Good, workable test gear is key to enabling our hobby. In this post we will discuss where to procure it at rock-bottom prices, what to look for, how to fix it, and how to tailor your laboratory practices around gear that may not be reliable.

We are lucky to be living in an era with plentiful high-quality test gear. Since the Second World War, surplus test gear has been in abundance at low costs enabling hobbyists, innovators, and academics to experiment and build great things. If you are willing to think before you measure you can save serious amounts of money and have a professional laboratory in your home.

Where to buy
The obvious answer is eBay, but the deals on test equipment are at the hamfests. Don’t be fooled by the name. Hamfests sell much more than amateur radio equipment. Hamfests are swap meets where hobbyists trade electronics of all kinds. Check out the ARRL hamfest calendar to find the next local one near you! I suggest you arrive early, however. The culture of hamfests tends to favor showing up as soon as the doors open and leaving about two hours before the official end. The early bird gets the worm!

Photos from a local hamfest showing an abundance of test gear (photos courtesy of Scott Pastor KC8KBK).

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DIY Vacuum Former On The Cheap

October 19, 2014 by Rich Bremer 26 Comments

Vacuum Forming is a process used to mold plastic into a desired shape. A thin sheet of plastic is heated to a soft state and then air pressure is used to press the plastic down around or into a mold. Vacuum forming can be used to make a variety of items, anything from product packaging to bath tubs.

That being said, a vacuum former is probably one of those things that would be nice to have around but may not get a lot of use. Therefore, spending any significant amount of money on one would result in a low-value situation. For some folks, building one from scratch may be the way to go. [Amalgamized] built his own low-cost vacuum former and did a great job documenting the build.

There is a two-pronged attack to keep the costs down on this project. First, the frame is made from readily available materials that you probably have kicking around in your wood scrap bin. The sides of the frame are 3/4″ plywood and the hole-filled top is made from 1/4″ MDF. A piece of PVC pipe connects the chamber below the top piece of MDF to a shopvac. The shopvac pulls the air down through the top’s holes; think reverse air hockey table.

Attack prong #2 is that there is no dedicated heater. Binder clips secure the plastic sheets to an aluminum window frame which are then put in the oven for a few minutes between 250 and 300ºF. When the plastic starts to droop, it is quickly removed from the oven and placed over a mold. The shopvac creates a low pressure zone under the plastic and atmospheric pressure pushes the plastic down around the mold.

Don’t You Just Love Comic Sans?

October 18, 2014 by James Hobson 29 Comments

Trick question! Of course you do, everyone loves Comic Sans! It’s only like the best font in the history of the internet! Why would you ever use anything else?

Oh! Is it because you feel like writing your novella on a computer is cheating? You wish you could use Comic Sans on your classic Sears-branded Brother Charger 11 typewriter from the 70’s? Don’t worry, we’ve got you covered.

Jokes aside, this is actually a pretty clever hack. He’s modified a typewriter to use custom letters which he has laser cut out of acrylic and super glued to the strikers of the typewriter. Continue reading “Don’t You Just Love Comic Sans?” →

PCB Toner Transfer Method, Now Without The Transfer

October 12, 2014 by Rich Bremer 47 Comments

A common way to create a custom PCB at home is to do what is called the Toner Transfer Method. In this process, the trace layout of the board is printed out on a piece of special toner transfer paper that allows the ink to come off in the following step. The toner transfer paper is then put print-side-down on a copper clad PCB blank, heated and pressed with an iron. The heat and pressure from the iron transfers the toner from the paper to the copper. The exposed copper then is chemically removed, the previously applied toner protects the copper in the pad and trace areas. The toner is then removed using paint thinner.

That is a long process with many critical steps. [mlerman] wondered why no one was printing the toner directly to the PCB. He has been tinkering with printing directly on PCB blanks for 4 years now. He’s made hundreds of boards over that time and can now make a PCB in under 15 minutes.

The obvious route to take would be to modify a current laser printer to accept the much-thicker-than-paper PCB boards. A few printer models were tried but [mlerman] feels the Lexmark E260 works the best due to the cost, internal mechanical components and an easily modifiable manual feed system. There is also a Local Printer Utility that allows the majority of the printer parameters to be adjusted.

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