Online Logic Simulator Is Textual — No, Graphical

We have a bit of a love/hate relationship with tools in the web browser. For education or just a quick experiment, we love having circuit analysis and FPGA tools at our fingertips with no installation required. However, we get nervous about storing code or schematics we might like to keep private “in the cloud.” However, looking at [Lode Vandevenne’s] LogicEmu, we think it is squarely in the educational camp.

You can think of this as sort of Falstad for logic circuits (although don’t forget Falstad does logic, too). The interface is sort of graphical, and sort of text-based, too. When you open the site, you’ll see a welcome document. But it isn’t just a document, it has embedded logic circuits in it that work.

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Card Reader Lockout Keeps Unauthorized Tool Users at Bay

It’s a problem common to every hackerspace, university machine shop, or even the home shops of parents with serious control issues: how do you make sure that only trained personnel are running the machines? There are all kinds of ways to tackle the problem, but why not throw a little tech at it with something like this magnetic card-reader machine lockout?

[OnyxEpoch] does not reveal which of the above categories he falls into, if any, but we’ll go out on a limb and guess that it’s a hackerspace because it would work really well in such an environment. Built into a sturdy steel enclosure, the guts are pretty simple — an Arduino Uno with shields for USB, an SD card, and a data logger, along with an LCD display and various buttons and switches. The heart of the thing is a USB magnetic card reader, mounted to the front of the enclosure.

To unlock the machine, a user swipes his or her card, and if an administrator has previously added them to the list, a relay powers the tool up. There’s a key switch for local override, of course, and an administrative mode for programming at the point of use. Tool use is logged by date, time, and user, which should make it easy to identify mess-makers and other scofflaws.

We find it impressively complete, but imagine having a session timeout in the middle of a machine operation would be annoying at the least, and potentially dangerous at worst. Maybe the solution is a very visible alert as the timeout approaches — a cherry top would do the trick!

There’s more reading if you’re one seeking good ideas for hackerspace. We’ve covered the basics of hackerspace safety before, as well as insurance for hackerspaces.

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Hybrid Bench Power Supply Can Also Hit the Road

Everyone needs a bench power supply, and rolling your own has almost become a rite of passage for hackers. For a long time, the platform of choice for such builds seemed to be the ATX power supply from a computer. While we certainly still see those builds, a lot of the action has switched to those cheap eBay programmable DC-DC converters, with their particolored digital displays.

This hybrid bench and portable power supply is a good example of what can be accomplished with these modules, and looks like it might turn out to be a handy tool. [Luke] centered his build around the DPS3003, a constant current and constant voltage buck converter that can take up to 40-VDC input and outputs up to 32 volts at 3 amps. In bench mode, the programmable module is fed from a mains-powered 24-volt switching supply. For portable work, an 18-volt battery from a Makita drill slips into a 3D-printed adapter on the top of the case. The printed part contains a commercial terminal [Luke] scored on eBay, but we’d bet the entire thing could be 3D printed. And no problem if you change power tool brands — just print another adapter.

Those little eBay power supply modules have proven to be an enabling technology, at least judging by the number of clever ways we’ve seen them used lately. From this combination bench PSU and soldering iron supply to a portable PSU perched atop a battery, these things are everywhere. Heck, you can even reflash the firmware and make them do your bidding.

[via Dangerous Prototypes]

Review: FG-100 DDS Function Generator

I don’t have a signal generator, or more specifically I don’t have a low frequency signal generator or a function generator. Recently this fact collided with my innocent pleasure in buying cheap stuff of sometimes questionable quality. A quick search of your favourite e-commerce site and vendor of voice-controlled internet appliances turned up an FG-100 low frequency 1Hz to 500kHz DDS function generator for only £15 ($21), what was not to like? I was sold, so placed my order and eagerly awaited the instrument’s arrival.

The missing function generator is a gap in the array of electronic test instruments on my bench, and it’s one that maybe isn’t as common a device as it once might have been. My RF needs are served by a venerable Advance signal generator from the 1960s, a lucky find years ago in the back room of Stewart of Reading, but at the bottom end of the spectrum my capabilities are meagre. So why do I need another bench tool?

It’s worth explaining what these devices are, and what their capabilities should be. In simple terms they create a variety of waveforms at a frequency and amplitude defined by their user. In general something described as a signal generator will only produce one waveform such as a sine or a square wave, while a function generator will produce a variety such as sine, square, and sawtooth waves. More accomplished function generators will also allow the production of arbitrary waveforms defined by the user. It is important that these instruments have some level of calibration both in terms of their frequency and the amplitude of their output. It is normal for the output to range from a small fraction of a volt to several volts. How would the FG-100 meet these requirements? Onward to my review of this curiously inexpensive offering.

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Long PCB Shows Effects of Ludicrous Speed

Transmission lines can seem like magic. When you make use of them it seems strange that a piece of wire can block or pass certain frequencies. It is less common to use transmission lines with pulses and typically your circuit’s transmission line behavior isn’t all that significant. That is, until you have to move a signal a relatively long distance. [Robert Baruch] has been using a long PCB to test pulse behavior on a bus he’s working on. He actually has a few videos in this series that are worth watching.

What makes it interesting is that [Robert] has enough distance on the board to where light-speed effects show up. By using a very nice DPO7104 oscilloscope and a signal generator, he shows how the signal reflects on the line at various points, adding and subtracting from it. The measurements matched theory fairly closely. You shouldn’t expect them to match exactly because of small effects that occur randomly throughout the system.

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Dark Field Microscopy on the Cheap with a PCB

It might seem like a paradox that you want a dark field to see things with an expensive microscope. As [IMSAI Guy] explains, a dark field microscope doesn’t make the subject dark. It makes the area surrounding the subject dark. After selling his expensive microscope, he found he missed having the capability, so he decided to make one cheaply. You can see how he did it in the video, below.

Dark field microscopy gives better contrast and resolution by discarding light that shines directly through or reflects directly from a sample. The only light you see is any that scatters. If you think about a normal microscope, you can imagine a cone of light coming from the top or the bottom. The tip of the cone hits the sample and then spreads back out into another cone of light. What hits your eye –well, actually, the eyepiece — is all the light from that cone. In a dark field instrument, the illumination cone is hollow — the light is just a ring. That means any light the sample doesn’t scatter gets blocked by a stop in the objective. When there is no sample, there’s no unblocked light, so you see a “dark field.”

Light that either refracts through the sample (from below) or bounces off a feature (from the top) will wind up in the hollow area that passes through the objective and you’ll see the image. It may surprise you that you may already have a piece of dark field technology on your desk. Optical computer mice that can work on glass surfaces use this same technique. If you want to see some examples and a diagram of how it all works, we did a post on a similar lower tech mod. There’s also Wikipedia.

The secret to doing this cheaply was to get a used dark field objective with a little rust on the barrel and then modify them with a custom PC board to create an LED ring light. This is different from the usual illuminator which shines a light through a patch stop to block the inner light. In this case, the light is made into a ring shape by virtue of the arrangement of the LEDs.

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DIY Pi Zero Pentesting Tool Keeps it Cheap

It’s a story as old as time: hacker sees cool tool, hacker recoils in horror at the price of said tool, hacker builds their own version for a fraction of the price. It’s the kind of story that we love here at Hackaday, and has been the impetus for countless projects we’ve covered. One could probably argue that, if hackers had more disposable income, we’d have a much harder time finding content to deliver to our beloved readers.

[ Alex Jensen] writes in to tell us of his own tale of sticker shock induced hacking, where he builds his own version of the Hak5 Bash Bunny. His version might be lacking a bit in the visual flair department, but despite coming in at a fraction of the cost, it does manage to pack in an impressive array of features.

This pentesting multitool can act as a USB keyboard, a mass storage device, and even an RNDIS Ethernet adapter. All in an effort to fool the computer you plug it into to let you do something you shouldn’t. Like its commercial inspiration, it features an easy to use scripting system to allow new attacks to be crafted on the fly with nothing more than a text editor. A rudimentary user interface is provided by four DIP switches and light up tactile buttons. These allow you to select which attacks run without needing to hook the device up to a computer first, and the LED lights can give you status information on what the device is doing.

[Alex] utilized some code from existing projects, namely PiBunny and rspiducky, but much of the functionality is of his own design. Detailed instructions are provided on how you can build your own version of this handy hacker gadget without breaking the bank.

Given how small and cheap it is, the Raspberry Pi is gaining traction in the world of covert DIY penetration testing tools. While it might not be terribly powerful, there’s something to be said for a device that’s cheap enough that you don’t mind leaving it at the scene if you’ve got to pull on your balaclava and make a break for it.