Raspberry Pi

1836 Articles

Rasberry Pi Analog Input Using Only Passive Components

February 28, 2016 by 18 Comments

The Raspberry Pi is a very capable device whose hardware has been pushed to the limit in all sorts of interesting ways. But even the most ingenious of experimenters have to agree on one point; it doesn’t possess an analog-to-digital converter. If you want analog inputs you will have to buy or build them.

[Mincepi] has done just that, but not as you might expect by adding an integrated circuit on one of the Pi’s interfaces. Instead the circuit [Mincepi] is using consists only of passive components, measuring the time taken to discharge the parasitic capacitance of one of the Pi’s inputs from logic 1 voltage to logic 0 voltage through a resistor into the voltage to be measured. This is a long-established approach to A to D conversion, one that was achieved back in the day with purpose-designed timers as microprocessor ancillaries.

The problem is that the Pi does not have a timer peripheral, so [Mincepi] has used the shift registers that form part of the Pi’s SPI and PCM inputs to perform this task on two channels. A sample rate of 100kHz and 6-bit resolution is claimed, with enough voltage range for a 1V peak-to-peak audio signal to be sampled.

Of course, simplicity does not guarantee a good ADC, and this circuit does not perform very well. It is noisy, non-linear, and as [Mincepi] puts it, probably sensitive to temperature. And though [Mincepi] talks in detail about the software to drive it, none is forthcoming. To quote: “It doesn’t include code since I’m in the process of writing a proper sound device module. My previous code was a simple character device, but it worked just fine, and served to prove the concept.”

We really want this to work, even if it’s not the best ADC ever. So we eagerly await the sound device module, and look forward to more news from the project.

This may be the simplest of simple ADCs we’ve yet featured here on Hackaday, but it’s not the first we’ve seen. There is this one using a comparator for example, or this one using a flip-flop. It is the essence of creative electronics to eke a function from a component that was never meant to be, please keep them coming!

An Internet Radio In A Classic Cathedral Case

February 27, 2016 by 13 Comments

If you’re looking for a hot collectible item and a great restoration project, cathedral-style radios from the 1930s are a solid choice. But they’re getting harder to find as the years roll by, so if your heart’s content is to listen to modern broadcasts through a radio with a classic look, you may need to roll your own cathedral case for an internet radio.

The cathedral-style case was a hugely successful form-factor for radios back in the day, with variations on the arch-top theme ranging from Gothic to Art Deco. For this build, [nick.r.brewer] decided on a more parabolic arch. His build log has SVG files for the individual ribs that were cut from plywood with an X-Carve. A Raspberry Pi and TFT display were mounted inside the finished case, along with a Bluetooth module and a 20W amplifier and speaker. A big 3-pole rotary switch with custom knob selects the audio source and evokes that 1930s feel. It ended up looking pretty good, and the video after the break shows that it sounds nice, too.

We featured a fair number of internet-radio-in-a-classic-case builds before, but we’re surprised to see no cathedral-style radios have been modded. Maybe it’s time to hit the flea market and estate sales and see what turns up.

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CNC Scrapbooking With A Raspberry Pi

February 25, 2016 by 14 Comments

It is perhaps a surprise that the widespread adoption of CNC machinery in the home has not come from 3D printing or desktop mills, but as a quiet revolution in the crafting industry. CNC cutters for plastic or card have been around for quite a while now, and while the prospect of cutwork greetings cards might not set all maker pulses racing these cutters do have significant untapped potential in other directions. Perhaps you have to own a carburetor whose gaskets have been unavailable since the 1960s to truly appreciate that.

[James Muraca] has a KNK Force, something of an object of desire in the world of desktop CNC cutters. The computer inside the Force is a Raspberry Pi, so of course [James] set about investigating its potential for running his own software. His progress so far is on GitHub, a web interface through which you can upload and cut an SVG file, but his plans are more ambitious. He hopes to turn his machine into a complete PCB manufacturing station, able to both cut the PCB, and with the addition of a vacuum attachment to pick and place components.

The KNK Force is an interesting machine not just because it is powered by a Raspberry Pi. Its cutter head is a rotary tool with a Z axis, so it can perform more heavy-duty and complex cutting tasks than its competition. In addition it has a camera built-in, and it is this feature that [James] hopes to use in his PCB project.

We’ve covered plenty of cutter projects before, from projects turning CNC machines and pen plotters into vinyl cutters to using a cutter as a laser engraver and even cutting solder paste stencils with one. We look forward to further progress on [James’s] project.

Giving The Pi Zero USB, Ethernet, And Serial Over USB

February 25, 2016 by 55 Comments

Just as the USB port on your phone can serve as a serial connection, mass storage device, and a network connection, the Pi Zero can do the same. We’ve seen a few people turn the Zero into a single USB gadget, but what about turning the Zero into a USB HID device, network connection, and serial port all at the same time? That’s what [Tobias] did, and his method is even easier than the old one.

The old method of turning the Pi Zero into a USB device required the user to modify and recompile the kernel. Obviously, this isn’t an ideal solution. [Tobias]’ implementation fixes this by putting everything into userland. Everything is configurable through a script and a few tweaks to how the Pi starts up.

The result is a Raspberry Pi Zero that will appear as any USB peripheral. [Tobias] goes through the usual examples: setting the Pi up as a serial device for hacking and code cracking in a terminal, as an Ethernet device to give the Pi Zero networking capabilities, as a keyboard to send keypresses to another computer, and as a mass storage device so that other computers can read a small portion of the Pi’s SD card.

There are plenty more USB gadgets the Pi can emulate, from printers to audio devices to MIDI adapters to webcams. If you can wrap your head around what a Pi Zero could do when configured as one of these devices, drop a note in the comments.

Picture Frame Mashup Taps Subreddits For “Deep Thoughts”

February 24, 2016 by 17 Comments

Remember “Deep Thoughts by Jack Handey”? We do, and we always enjoyed the quirky mix of soothing music, soft-focus nature images, and random absurd thought scrolling across the screen as bumpers between segments on Saturday Night Live. Clearly, [tvm78] remembers them, because his picture frame mashups of the r/EarthPorn and r/ShowerThoughts subreddits could have been written by Jack himself.

While [tvm78] shares no photos of his build and offers no tutorials, he makes it clear that this was his first build of any kind. He does offer a few details, like the fact that he’s driving a display with a Raspberry Pi, and he handily references a similar build that includes the code he borrowed to make his frame happen. While we feel that the original mashup works well, several helpful redditors offer suggestions for other combinations, like r/ArchitecturePorn and /r/nocontext, or r/abandonedporn and r/onelinehorror. Of course a straight grab from r/demotivational could be fun too.

We’ve seen tons of web-enabled picture frames before, and plenty of “magic mirror” builds that display useful information on a two-way mirror. But this one appeals to the cynic in us, and would make Jack Handey proud.

Add A Slide Show To Your Fish Tank

February 24, 2016 by 11 Comments

Once in a way we get a hack that makes us wonder – why didn’t we think of that ? [hydronics] tore apart an old LCD monitor and built a fish tank around it. Not sure if the fish notice that they are swimming on the Moon, but it sure makes for an interesting fish tank display.

He starts by ripping apart an old 19″ LCD monitor and built an acrylic fish tank around the display. The backlight of the panel is fixed at the rear side of the fish tank, along with the rest of the electronics from the old monitor.

For an earlier version, he built his own back light, but the second version with the original back light turned out much better. The fish tank pieces were joined together using acrylic glue and left over night to dry, although he still needed to use some silicone to plug leaks.

A Raspberry Pi connected to the monitor’s HDMI input provides the background slide show. [Tony Rieker] helped add bubble animations via some OpenCV code running on the Pi. A live feed of the fish is overlaid on the slide show, adding a level of inception to this tricked up fish tank. The project was recently shown off at the Portland Winter Light Festival.

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