raspberry pi

1660 Articles

POV Globe Display Spins Up Full Color Tupac

December 24, 2015 by 11 Comments

Persistence of vision projects were once all the rage, judging by a quick review of the literature here on Hackaday. They’ve tapered off a bit lately, but this impressive full-color globe display might just kick-start some new POV projects.

Built as a final project for an EE course, [Evan] and [Kyle]’s project is more about the control electronics and programming than the mechanical end of the build. Still, spinning a 12″ ring of 1/4″ thick acrylic with a strip of APA102 LEDs glued to the edge takes some thoughtful engineering. While the build appears sturdy, [Evan] does admit to a bit of wobble under full steam, which was addressed by adding some weight to the rig. We wonder if mounting half the LEDs on each side of the ring to balance the forces wouldn’t have worked better. True, it would have complicated the coding for the display, but maybe that would have been good for extra points. In any case, the display turned out well and the quality of the images is great. And as an aside: how awesome is it that we live at a time when you can order a six-circuit slip-ring for a project like this for less than $20?

It’s the end of the semester and we love seeing the final projects that have just made it across the finish line. This globe is one, yesterday we saw a voice-controlled digital eye exam, and if you have or know of a final project, don’t forget send us the link!

If POV globes are your thing, be sure to set the Hackaday WABAC machine a few years and check out this Death Star design from 2012 or this globe from 2010.

Raspberry Pi Laser Beam Profiler

December 21, 2015 by 3 Comments

[Anthony] at UCLA needed to verify the shape of a laser beam. Commercial units for this, as you would expect, are expensive. But a Raspberry Pi with a Pi Noir camera easily handles the task. Not only is the use of the Pi cool but so is the task – they are using lasers to cool molecules to study quantum effects. The Pi camera without the IR filter captures a wide bandwidth making it suitable for use with non-visible lasers. [Anthony] captures the beam along two axes and plots both curves on the LCD touchscreen. That data, based on the pictures, is also available on a host PC. All this in a super compact package with a 7″ touch screen display.

2D crystal of Yb ions.

One reason I find this fascinating is I did something similar 1977 at the University of Rochester Laboratory for Laser Energetics. My project was measuring the energy cross-section of a laser beam. The research goal of the Laboratory was the study of inertial confinement laser fusion. While [Anthony] uses an entire camera my project was limited to a 1 dimensional array of charge coupled devices (CCD). The output went to a Tektronix storage terminal and was printed on thermal paper for reference. He uses Python running on the target system. My work used a Z80 development system the size of a tower PC to write my program in assembly language which was then executed on a single board computer. We’ve come a long way. My code is long gone but you can get [Anthony’s] on GitHub.

Open Sesame Raspberry Pi Style

December 17, 2015 by 5 Comments

[Don] installed an Android tablet into his wife’s vehicle and realized he wanted to allow it to operate and monitor the garage door. His biggest challenge? Meeting the (what he refers to) as the WAF or Wife Acceptance Factor. He decided to use a Web app on a Raspberry Pi, along with a handful of switches and a relay. His list of goals were straightforward:

  • Provide the status of the door (open/closed/unknown)
  • Open and close the door
  • Work across multiple platforms
  • Secure enough to connect to the Internet
  • Reliable and simple

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Better Networking With A Macintosh Classic

December 15, 2015 by 18 Comments

While it may not be the case anymore, if you compare a Mac and a PC from 1990, the Mac comes out far ahead. PCs suffered with DOS, while the Mac enjoyed real, non-bitmapped fonts. Where a Windows PC required LANMAN to connect to a network, the Mac had networking built right into every single machine. In fact, any Mac from The Old Days can use this built-in networking to connect to the Internet, but most old Mac networking hacks have relied on PPP or other network to serial conversion. [Pierre] thought there was an incomplete understanding in getting old Macs up on the Internet and decided to connect a Mac Classic to the Internet with Apple’s built-in networking.

Since the very first Macintosh, Apple included a simple networking protocol that allowed users to share hard drives, folders, and printers over a local network. This networking setup was called LocalTalk. It wasn’t meant for internets or very large networks; the connection between computers was basically daisy chained serial cables and later RJ-11 (telephone) cables.

LocalTalk stuck around for a long time, and even now if you need to do anything with a Mac made in the last century, it’s your best bet for file transfer. Because of LocalTalk’s longevity, routers and LocalTalk to Ethernet adapters can be found fairly easily. The only problem is finding a modern device that speaks both TCP/IP and LocalTalk. You can’t use a new Mac for this; LocalTalk has been gone from OS X since Snow Leopard. You can do it with a Raspberry Pi, though.

With a little bit of futzing about with MacTCP and a few other pieces of software from 1993 or thereabouts, [Pierre] can even get his old Mac Classic online. Of course the browsers are all horribly outdated (making the Hackaday retro edition very useful), but [Pierre] was able to load up rotten.com. It takes a while with an 8MHz CPU and 4MB of RAM, but it does get the job done.

You can check out [Pierre]’s demo video below.

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Maker Barn Organizer Creates Makerspace Access Control System

December 13, 2015 by 15 Comments

The MakerBarn is a new makerspace between The Woodlands and Tomball, TX (north of Houston). [George Carlson], one of the founders and a retired design engineer, wanted to make sure only members certified on a machine could use it. He worked with [Kolja Windeler] to create the MACS or Makerspace Access Control System. He has one video explaining MACS and, after the break, another explaining the browser based user interface for the system.

20151205_181615A control box, [George] calls them stations, controls the power to a machine. Member badges have an RFID tag that is read when inserted into the station’s reader. If the member is authorized to use the machine, the power is enabled. For safety, the member’s badge must remain in the reader to maintain power. The reader uses a Photon board from Particle with a WiFi link to a Raspberry Pi server.

[Kolja] developed a Pi system to maintain a database of member numbers and the machines they can use. The list is sent to the stations periodically or when updates occur. The user interface is browser based on the MakerBarn’s LAN so it can be maintained by a computer or smartphone in the space. Presently 21 MACS modules have been built with some going to Hanover University in Germany for their auto hobby shop.

Not only did [George] lead the effort on creating MACS but has been key to getting the construction done inside a pole barn to make the MakerBarn a reality.

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Turning A Pi Into A PDP

December 12, 2015 by 28 Comments

There’s no better way to learn how to program a computer than assembly, and there’s no better way to do assembly than with a bunch of blinkenlights and switches. Therefore, the best way to learn programming is with a PDP-11. It’s a shame these machines are locked up in museums and the garages of very cool people, but you can build your own PDP-11 with a Raspberry Pi and just a few extra components.

[jonatron] built his own simulated version of the PDP-11 with a lot of LEDs, a ton of switches, and a few 16-bit serial to parallel ICs. Of course the coolest part of any blinkenlight simulator are the front panel graphics, and here [jonatron] didn’t skimp. He put those switches and LEDs on a piece of laser cut acrylic with a handsome PDP11 decal. The software comes with a load of compiler warnings and doesn’t run anything except for very simple machine code programs. That’s really all you can do with a bunch of toggle switches and lights, though.

If this project looks familiar, your memory does not deceive you. The PiDP-8/I was an entry in this year’s Hackaday Prize and ended up being one of the top projects in the Best Product category. We ran into [Oscar], the creator of the PiDP-8, a few times this year. The most recent was at the Hackaday SuperConferece where he gave a talk. He’s currently working on a replica of the king of PDPs, the PDP-11/70.

Video below.

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Raspberry Pi Communication Via LASER

December 12, 2015 by 28 Comments

[Nick Touran] wanted to make two Raspberry Pi’s communicate wirelessly. There are lots of options, but [Nick] used a LASER and a photoresistor, along with Morse code. If you don’t find Morse code fancy enough, you could always refer to it as OOK (on/off keying). The circuit uses a common LASER module and an ordinary photoresistor that varies in resistance based on light. A resistor forms a voltage divider with the photoresistor and an external A/D reads the resulting voltage.

The circuit works, but we couldn’t help but notice a few items. Not all photoresistors are as sensitive to the same light wavelengths, so for the maximum range you’d want to pick a particular photoresistor.  While the analog to digital converter is certainly workable, we couldn’t help but wonder if you couldn’t set up the divider to use the inherent threshold of the Raspberry Pi’s input pins for a simpler circuit. Of course, if you used the same technique with an Arduino, you could use the built-in A/D converter, and the A/D converter is probably easier to get working.

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