Turning An Analog Scope Into A Logic Analyzer

scope

When [Marco] was planning on a storage oscilloscope build, he realized having a small device to display eight digital signals on an analog scope would be extremely useful. This just happens to be the exact description of a simple logic analyzer and managed to turn his idea into a neat little project (German, Google translation).

The theory of operation for this surprisingly simple, and something that could be completed in a few hours with a reasonably well stocked hackerspace or parts drawer in a few hours. A clock generator and binary counter are fed into the lower three bits of a simple R2R DAC, while the 8 inputs are fed into an 8-input multiplexer and sent to the last bit of the DAC. With nothing connected to the logic analyzer inputs, the output to the scope would just be an 8-step ramp that would appear as eight horizontal lines on the screen. With something connected to the logic analyzer input, an extremely primitive but still very useful logic analyzer appears on the screen.

While it’s not the greatest analyzer, it is something that can be cobbled together in an hour or two, and the capabilities are more than sufficient to debug a few simple circuits or figure out some timings in a project.

The Beginnings of an LCR Meter

LCR Meter

The inductor is an often forgotten passive electrical elements used to design analog circuitry. [Charles's] latest proof of concept demonstrates how to measure inductance with an oscilloscope, with the hopes of making a PIC based LCR meter.

It is not that often one needs to measure inductance, but inductors are used in switching regulators, motor circuits, wireless designs, analog audio circuitry, and many other types of projects. The principles of measuring inductance can be used to test inductors that you have made yourself, and you can even use this knowledge to measure capacitance.

[Charles] originally saw a great guide on how to measure impedance by [Alan], and decided to run with the idea. Why spend over $200 on an LCR meter when you can just build one? That’s the spirit! Be sure to watch [Alan's] and [Charles's] videos after the break. What kind of test equipment have you built in order to save money?

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A USB Connected Box-o-Encoders

picoscope-encoder

[Colin] loves his PicoScope, a USB based “headless” oscilloscope. While using it he found himself longing for a classic oscilloscope interface. Mouse clicks just weren’t a replacement for grabbing a dial and twisting it. To correct the situation he created his USB-Connected Box-o-Encoders. The box maps as a USB keyboard, so it will work with almost any program.

[Colin] started by finding encoders. There are plenty of choices – splined or flatted shaft, detents or no detents, panel, PCB, or chassis mount. He settled on an encoder from Bourns Inc. which uses an 18 spline shaft. His encoder also includes a push button switch for selection. With encoders down, knobs were next. [Colin] chose two distinct styles. The two knob styles aren’t just decorative. The user can tell which row of knobs they are on by touch alone. Electronics were made simple with the use of a Teensy++ 2.0. [Colin] used a ATUSBKey device running Teensy software, but says the Teensy would have been a much better choice in terms of size and simplicity.

Once everything was wired into the box, [Colin] found his encoders would “spin” when the knobs were turned. They are actually designed to be PCB mounted, and then screwed into a control panel. Attempts to tighten down the panel mounting nut resulted in a broken encoder. Rather than redesign with purely panel mounted encoders, [Colin] used a dab of epoxy to hold the encoder body in place.

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Oscilloscope Repair Projects Still Probing For Success

lecroy-9450-oscilloscope-repair[Luke] isn’t able to declare total victory yet. His LeCroy 9450 oscilloscope repair project has seen some success, though. The glitchy screen seen above is just one of the problems it had, but has now been fixed. When [Luke] got his hands on it, this was one of three screen states: the other two being normal operation or completely dead. Replacing the screen connector was all it took, so he moved on to the second part.

This one is much less trivial. Only one of the two channels works—which might be the point at which many would abandon the repair—but it’s still a fine single-channel scope. [Luke] continued to trouble-shoot by disassembling the bottom of the case and breaking out the device’s schematics. He traced the circuit and found one module that is suspect (and is looking for help finding a replacement). Unfortunately, the problems don’t end there. Another unknown problem is causing erroneous signals on the displayed waveforms. It’s an odd issue but it really feels like he’s close to solving this one!

A Video Vectorscope Oscilloclock

Tek 520A Oscilloclock

Back in the days of analog TV, vectorscopes were used to view video signals. [Aaron] has taken an old Tek 520A NTSC vectorscope and converted it into his newest oscilloclock.

The scope was originally designed to look at the signal provided by composite video. It draws vectors on a polar plot. By using test patterns such as color bars, you can ensure equipment is creating the correct color output. These scopes were so commonly used that many digital systems still provide a simulated vectorscope for color analysis. Vectorscopes were designed to be left on constantly, which is a good quality for a clock.

[Aaron] has a history of converting oscilloscopes into clocks, which we have featured in the past. This build is similar, using his custom control hardware to drive the display. Since analog vectorscopes are pretty much obsolete, you can find them on eBay at low prices, so these oscilloclocks could be relatively cheap to build.

In the write up, you get a teardown of the Tek 520A, showing the modifications made to build the clock. After the break, check out a video of the Tek 520A Oscilloclock.

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Hackaday Links: January 12, 2014

hackaday-links-chain

[Kyle] teaches photography and after being dismayed at the shuttering of film and darkroom programs at schools the world over decided to create a resource for film photography. There’s a lot of cool stuff on here like mixing up a batch of Rodinal developer with Tylenol, lye, and sodium sulphite, and assessing flea market film cameras. There are more tutorials coming that will include setting up a dark room, developing prints, and playing around with large format cameras.

[hifatpeople] built a binary calculator out of LEGO® bricks or toys. It started off as a series of logic gates built out of LEGO® bricks or toys in the LEGO® Digital Designer. These logic gates were combined into half adders, the half adders combined into full adders, and the full adders combined into a huge plastic calculator. Unfortunately, buying the LEGO® bricks or toys necessary to turn this digital design into a physical model would cost about $1000 using the LEGO® Pick-A-Brick service. Does anyone have a ton of LEGO® Technic® bricks or toys sitting around? We’d love to see this built.

Think you need a PID controller and fancy electronics to do reflow soldering in a toaster oven? Not so, it seems. [Sivan] is just using a meter with a thermocouple, a kitchen timer, and a little bit of patience to reflow solder very easily.

The folks at DreamSourceLabs realized a lot of electronic test equipment – from oscilloscopes and logic analyzers to protocol and RF analyzers were all included a sampling circuit. They designed the DSLogic that puts a sampler and USB plug on one board, with a whole bunch of different tools connected to a pin header. It’s a pretty cool idea for a modular approach to test equipment.

Adafruit just released an iDevice game. It’s a resistor color code game and much more educational than Candy Crush. With a $0.99 coupon for the Adafruit store, it’s effectively free if you’re buying anything at Adafruit anytime soon. Check out the video and the awesome adorable component “muppets”.

Fubarino Contest: Oscilloscope Clock

fubarino-contest-oscilloscope-clock

Before hearing about the Fubarino Contest [Joseph] never considered adding an Easter Egg to one of his own projects. But after seeing so many contest entries we think this is just the kind of fun extra that needs to make its way into every design!

The subject of his entry is an oscilloscope clock which displays our URL instead of the numbers usually found on a clock face. He’s using a SparkFun board to generate the clock — a piece of hardware we saw about 18 months ago hidden inside of a vintage scope. The feature is unlocked only when displaying roman numerals in combination with a special serial command.

Replacing the numerals with the URL isn’t entirely straight-forward. Since an oscilloscope is a vector display [Joseph] actually had to build his own array of start and end coordinates for each character. Luckily he did a fantastic job of documenting this which will allow you to make it say anything you wish.


This is an entry in the Fubarino Contest for a chance at one of the 20 Fubarino SD boards which Microchip has put up as prizes!