Redlining Your CPU Via Automotive Tachometer

December 14, 2014 by Matt Freund 15 Comments

Many CPU-usage widgets have stylistically borrowed from vehicles, displaying something mimicking the tachometer found in the dashboard. [Pat] took it a step further and tried his hand at re-borrowing this style. He figured, why not use an actual physical tachometer to display how hard the CPU on his Raspberry Pi was revving?

With the goal of tuning 0-100% CPU usage to 0-8000 RPM on the tach, the first step was diagnosing the range of PWM input frequencies that moved the needle across the tach’s full arc. Using his Tektronix 3252C function generator he quickly determined 0-440 Hz would be needed and graphed a handful of intermediate points. The response curve was not linear, so he drew up some fudging guidelines to make all the datapoints match.

Next, he wrote a few lines of Python (he shared) to make the Pi to poll its CPU usage and translate it to the proper frequency. The Pi makes outputting easy, GPIO pin 11 carried the signal to a 7404 for buffering, then out to the tach. The automotive tach itself ran on 12V, but its input signal required only 5V so he pulled a 7805 from his parts bin.

Once it was all put together it worked beautifully using just the one extra component. Some might see this as more clever than USB dependent or Arduino ~~bloated~~ based tachometer hacks.

See the video after the break of the tach twitching even when the mouse moved, and pegging the red when opening a browser. No more need to use up valuable screen real-estate (or use a screen at all) if you want to see at a glance when your Pi is putting in work.

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1.37″ CRT Restored By Hacklab For Miniature MAME Cabinet

December 13, 2014 by Matt Freund 27 Comments

For $5, [William] of Toronto’s Hacklab hackerspace got a hold of one of the smallest CRT screens ever made – about the size of a large coin. Over the course of a couple sessions – including a public hack boothside at their Mini Makerfaire – [William], [Igor], and several other members managed to connect it as a monitor directly off a Raspberry Pi. The end-goal is the world’s smallest MAME cabinet (smaller by almost half than this LCD one).

As Canada followed the US and stopped broadcasting analog back in 2011, it became quite a challenge to feed the screen a video source. They disclosed early that the easiest solution would just be an RF transmitter on the Pi and then tune the micro-set to that channel. Too easy. They wanted something elegant and challenging so they went digging into the circuitry to find a place to insert a composite video signal directly.

The real story here is their persistence at reverse engineering. The PCB was folded like a cardboard box to fit in the original case, making large portions of the circuitboard and wiring inaccessible. Even when they managed to trace the signal to what they thought was the appropriate chip (marked C80580), they could not find any information on the 30 year old chip. Noting that every other chip on the board was Panasonic and started with “AN5”, [Igor] suspected the mystery silicon was just renamed and went through every single datasheet he could find with that prefix. Combined with form factor, pin count and purpose, his sleuthing was rewarded with a guess for a match – the AN5715. His hunch was correct – using that datasheet led him to the answers they required.

Then they just had to figure out how get the composite signal the Pi outputted into something the chip would use to display the correct image. There were no shortage of challenges, failures and dead ends here either, but they had help from the rest of their membership.

Their project log is an interesting narrative through the process and in the end of course, it worked. It is displayed beautifully with a clear acrylic case and ready for a cabinet to be built.

Raspberry Pi Powered Super Digital Photo Frame

December 11, 2014 by Rich Bremer 21 Comments

HaD reader [Greg] just finished an LCD picture frame project he’s been working on for a while. This is no ordinary photo display. His brother came up with the idea of having a device to display photos that could be changed remotely. [Greg] gave it some thought and came up with a plan; use a Raspi as the brains, connect to the internet via WiFi and display photos stored in a specific Google Drive folder. Any authorized user can upload photos remotely to the frame so the frame-owner has a constant stream of new photos to view.

Of course, using an off-the-shelf picture frame may have been too easy. Instead [Greg] decided to start with an old computer monitor and wrap it in a wooden frame so it looks good. Mounted to the back of the LCD is a Raspberry Pi with a USB WiFi dongle. The monitor runs at 14 VDC and luckily has an external power supply. Since the Pi runs at 5 V, a buck converter taps into the LCD’s input power and outputs a Pi-happy 5 volts.

This project doesn’t stop with displaying photos! The user can also switch to a weather view. The weather image displayed is generated from weather data pulled from the internet in the exact same manor used by folks who make stand-alone weather displays out of old Kindles. Oh yeah, switching between photos and weather is done by wireless remote! On the frame unit itself there is only one button, but it has 3 functions: A quick press turns the screen off, a short hold syncs with Google Drive and a long hold powers off the RaspPi.

If you’d like to make your own frame, [Greg] has graciously made all his scripts available for download…. not to mention his very detailed build log.

Vintage Apple Keyboard Revived As Standalone Computer

December 10, 2014 by Matt Freund 23 Comments

Many of our readers are familiar with the gold standard of classic PC keyboards – the bunker with switches known as the IBM Model M. The Model M’s Apple contemporary is the Apple Extended Keyboard and they are just as highly sought-after by their respective enthusiasts. Though discontinued almost 25 years ago and incompatible with anything made in the last 15, the codenamed “Saratoga” is widely considered the best keyboard Apple ever made.

[Ezra] has made a hobby of modernizing these vintage heartthrobs and rescuing them from their premature obsolescence. In a superbly documented tutorial he not only shows how to convert them to USB (a popular and trivial hack), but teaches you how and where to smuggle a Raspberry Pi in as well.

After disassembly, the project requires only a little bit of chisel and Dremel work before the soldering iron comes out. [Ezra] was fairly meticulous in removing or redirecting the Pi’s connectors and hardwiring the internals. Only 3 pins need to be traced from the original keyboard and [Ezra]’s ADB–>USB Rosetta Stone of choice is the Hasu Converter running on a Atmega 32u4 clone. Balancing cost, range, and power draw from the Pi, he settled on the TP-LINK WN722N for his WiFi solution which is also tucked away inside the case. A single pullup resistor to finish it off and [Ezra] was delighted to discover it worked the first time he plugged it in.

Keyboards from this era use actual momentary switches that audibly click twice per keypress. In our world of screens-as-keys celebrating the lack of tactile constraints, using beasts like the Model M or the AEK to force transistors to do your bidding is like racking a shotgun during a game of lasertag – comically obtuse but delightfully mechanical.

If you are looking to expand on [Ezra]’s tinkering, he has already made a wishlist of additions: a toggle switch to lobotomize the Pi back into a plain USB keyboard, an internal USB hub, and a power switch.

Hear the video of an AEK in action after the break (or loop it to sound productive while you nap).

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Build Your Own Raytracing Minion

November 30, 2014 by Adam Fabio 13 Comments

A canceled project left [Craig] with six Raspberry Pi based devices he calls “Minions”. A minion is a Raspberry Pi model A in a small enclosure with an Adafruit 2.2″ 320×240 SPI LCD. The LCD lives in a lollipop style circular housing above the base. [Craig] has found a use for one of his minions as a desktop raytracer.

The Raspberry Pi is quite capable of running Persistance Of Vision Raytracer, or POV-Ray. POV-Ray started life as an early PC based raytracer. Created as a port of an Amiga program called DKBTrace, which was itself a port of a Unix raytracer, POV-Ray first was released in 1987. For the uninitiated, raytracers like POV-Ray literally trace rays from a light source to an image plane. As one would imagine, the Raspberry Pi’s little ARM processor would take quite a bit of time to raytrace a high resolution image. However, when targeting a 320×240 LCD, it’s not half bad.

[Craig’s] minion is running his own software which he calls ArtRays. Based upon a setup file, ArtRays can render images from several sources, including the internet via a WiFi dongle, or a local SD card. Rather than walk through the setup and software install, [Craig] has provided a link to download a full SD card image to build your own Minion. It might be worth experimenting on your own first though, rather than killing his server with a 1GB download.

We’re glad [Craig] has found use for one of his minions, now we have to see what he’s done with the other five!

Hacklet 24 – Raspberry Pi Projects

November 28, 2014 by Adam Fabio 7 Comments

Experimenting with embedded Linux used to mean reformatting an old PC, or buying an expensive dev board. In February of 2012, the Raspberry Pi was released, and it has proven to be a game changing platform. According to the Raspberry Pi Foundation, over 3.8 million boards have been sold. 3.8 million translates into a lot of great projects. This week’s Hacklet focuses on some of the best Raspberry Pi projects on Hackaday.io!

We start with [richardginus] and the RpiFPV (aka Raspberry Pi First Person View) project. [Richardginus] is trying to build a low latency WiFi streaming camera system for radio-controlled models using a Raspberry Pi and camera. He’s gotten the system down into a respectable 160 milliseconds on the bench, but in the field interference from the 2.4GHz R/C transmitter drives latency way up. To fix this, [Richardginus] is attempting to control the plane over the same WiFi link as the video stream. We’d also recommend checking out some of those “outdated” 72 MHz R/C systems on the used market.

Next up is [James McDuffie] and his RPi Holga. Inspired by [Peter’s] Holga camera project, [James] has stuffed a Raspberry Pi model A, a camera module, and a WiFi adapter into a Holga camera body. The result looks like a stock Holga. We saw this camera up close at the Hackaday 10th Anniversary event, and it fooled us – we thought [James] was just a lomography buff. It was only after seeing his pictures that we realized there was a Pi hiding inside that white plastic body! Definitely check out [James’] instructions as he walks through everything from hardware mods to software installation.

No Raspberry Pi list would be complete without a cluster or two, so we have [Tobias W.] and his 3 Node Raspberry Pi Cluster. The Raspberry Pi makes for a cheap and efficient platform to experiment with cluster computing. [Tobias] did a bit more than just slap a few Pis on a board and call it a day though. He custom machined an aluminum plate to hold his 3 node cluster. This makes wire management a snap. The Pi’s communicate through a four port Ethernet hub and all run from a single power supply. He even added a key switch, just like on the “old iron” mainframes. [Tobias] has been a bit quiet lately, so if you run into him, tell him we’re looking for an update on that cluster!

From [Tim] comes the PIvena, a Raspberry Pi laptop which takes its styling cues from [Bunnie Huang’s] Novena computer. Pivena is a bit smaller though, with a 7” HDMI LCD connected to the Pi. The case is made from laser cut wood and a few 3D printed parts. Everything else is just standard hardware. [Tim] kept the PIvena’s costs down by using a wooden kickstand to hold up the screen rather than Novena’s pneumatic spring system. The base plate of the PIvena includes a grid of mounting holes just like the Novena. There is also plenty of room for batteries to make this a truly portable machine. The end result is a slick setup that would look great at any Hackerspace. We hope [Tim] creates an update to support the new Raspberry Pi B+ boards!

Our Raspberry Pi-based alarm clock is chiming the hour, so that’s about it for this episode of the Hacklet! As always, see you next week. Same hack time, same hack channel, bringing you the best of Hackaday.io!

Custom Raspberry Pi Thermostat Controller

November 26, 2014 by Rick Osgood 13 Comments

Thermostats can be a pain. They often only look at one sensor in a multi-room home and then set the temperature based on that. The result is one room that’s comfortable and other rooms that are not. Plus, you generally have to get up off the couch to change the temperature. In this day and age, who wants to do that? You could buy an off-the-shelf solution, but sometimes hacking up your own custom hardware is just so much more fun.

[redditseph] did exactly that by modifying his home thermostat to be controlled by a Raspberry Pi. The temperature is controlled by a simple web interface that runs on the Pi. This way, [redditseph] can change the temperature from any room in his home using a computer or smart phone. He also built multi-sensor functionality into his design. This means that the Pi can take readings from multiple rooms in the home and use this data to make more intelligent decisions about how to change the temperature.

The Pi needed a way to actually talk to the thermostat. [redditseph] made this work with a relay module. The Pi flips one side of the relays, which then in turn switches the buttons that came built into the thermostat. The Pi is basically just emulating a human pressing buttons. His thermostat had terminal blocks inside, so [redditseph] didn’t have to risk damaging it by soldering anything to it. The end result is a functional design that has a sort of cyberpunk look to it.

[via Reddit]