Reading Analog Sensors With The Raspberry Pi

July 28, 2012 by Brian Benchoff 18 Comments

Adafruit just posted an awesome tutorial on reading analog sensors with the Raspberry Pi. It’s a great walkthrough that can be applied to your next Raspi project as well as any project where you just need one more analog input.

Earlier, the folks over at Adafruit posted a tutorial on using a MCP3008 ADC with the Raspi to directly read analog values using a Raspi. Sometimes, though, you don’t need eight analog inputs and a 12-bit ADC to get a project off the ground. Adafruit’s tutorial for reading analog values without an ADC relies on a single 1μF ceramic capacitor attached between a digital input and ground. By pulling the sensor line high for a millisecond or two, the capacitor charges at different rates depending on the value of the analog sensor.

Yes, it’s just an RC timing circuit but seeing as how the Raspi doesn’t have an analog input, we figure this tutorial could help out a few people.

Gaining Low-level SPI Access On The Raspberry Pi

July 27, 2012 by Mike Szczys 7 Comments

Raspberry Pi - rpi

We’ve seen a ton of projects that interface hardware with the Raspberry Pi. But they usually depend on bit-banging. That means they toggle the pins in software to match a specific protocol. The thing is that the beefy Broadcom SoC that anchors the board has a lot of built-in peripherals that are just waiting to be used instead of bit banging. In this case, it’s the hardware SPI peripheral which can be accessed via the bcm2835 library for RPi.

One of the things that would have really complicated this process is the pin mapping between the Broadcom chip and the RPi GPIO header. Since not all pins are broken out, it was either luck or good design forethought that made all of the SPI0 pins from the chip available on the RPi breakout header. The library page (linked above) explains this well. But if you’re looking for more of a working example check out [EngineerByNight’s] project with adds an accelerometer using hardware SPI.

Raspberry Pi Keeps Tabs On Your Solar Power Setup

July 25, 2012 by Mike Nathan 15 Comments

raspberrypi-solarlogger

[Brian Dorey] has been adding green power solutions to his home for some time now, and as things have progressed, he has experimented with several different iterations of data loggers. The latest system watching over his solar power setup is a Raspberry Pi armed with a custom-built I2C analog/digital converter.

The Rasp Pi is responsible for monitoring several different temperature sensors related to his solar water heating and storage system, but that’s just the beginning. It also keeps watch over his roof-mounted solar electric panels, his battery bank, and its charge controller. For good measure, he also monitors his home’s temperature and his water tank’s recirculation pump because, why the heck not?

All of the collected data is relayed to his web server where it is handsomely displayed for his perusal and analysis. [Brian] has made his code available here, so you can monitor your home in the same fashion with little fuss.

Raspberry Pi Case Roundup

July 24, 2012 by Jeremy Cook 38 Comments

If you haven’t heard of it yet, the [Raspberry Pi] is all the rage on [HAD] these days, so why not a round up of some of the excellent cases available?

[Nhslzt] wrote in to tell us about his laser cut Bramble Pi finger jointed case. These are available for only 12 Euros, or roughly $14.95 in the US. Sure, the exchange rate may not be in America’s favor these days, but it’s cheaper than a trip to Dresden, Germany where some of the profits from this are to go towards setting up a makerspace there!

If you’re feeling more into the additive 3D printing DIY process, why not just download one and make it on your printer? [Thingiverse] has an excellent selection of cases many featuring, as you may have guessed, a picture of a Raspberry on the top! (Here’s the printed case pictured).

Finally for something more colorful (see the pic after the break), you can’t get much better than the [Pibow]. If you’re looking for something colorful, and very solid (as described) this may be the case for you! You can order one here or use the unique design to inspire your own case (Thx Brian!).

As for stuff that we’ve already written about at HAD, this case looks quite slick made out of black acrylic, as does this one, combining the use of a laser cutter and 3D printer. Of course, if you’re going for the strictly utilitarian model, you can always go with one held together with rubber bands and tape!

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Real Life Subtitle Glasses

July 23, 2012 by Gerrit Coetzee 15 Comments

[Will Powell] sent in his real-time subtitle glasses project. Inspired by the ever cool Google Project Glass, he decided he would experiment with his own version.

He used two Raspberry Pi’s running Debian squeeze, vuzix glasses, microphones, a tv, ipad, and iphone as the hardware components. The flow of data is kind of strange in this project. The audio first gets picked up by a bluetooth microphone and streamed through a smart device to a server on the network. Once it’s on the server it gets parsed through Microsoft’s translation API. After that the translated message is sent back to a Raspberry Pi where it’s displayed as subtitles on the glasses.

Of course this is far from a universal translation device as seen in Star Trek. The person being translated has to talk clearly into a microphone, and there is a huge layer of complexity. Though, as far as tech demos go it is pretty cool and you can see him playing a game of chess using the system after the break.

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Servos, Servos, And More Servos

July 21, 2012 by Brian Benchoff 22 Comments

For one reason or another, a lot of Hackaday readers are doing stuff with servos as of late. Here’s a few servo hacks that made their way into our tip line over the past day or so:

USB servo controller and a Stewart Platform

[Patricio] needed a way to control a bunch of servos for his thesis project. He came up with a USB servo controller (Spanish, here’s the translation) powered by a 40-pin PIC 18F microcontroller. The board connects to the USB port of a computer and supports up to 8 servos with 8 additional digital I/Os. Why all this horsepower? It’s for a Stewart Platform [Patricio] and his partner [Natalia] built.

Continuous rotation servos

Standard servos are usually limited to a rotation angle of somewhere between 140 and 160 degrees. Sometimes you need a continuous rotation servo, and those are a little more expensive. Every servo is a continuous rotation servo if you disable a the variable resistor as [Valentin] shows us. It’s a simple, if old, hack. It’s new to someone, though.

Eight servos on a Raspi

[Mikael] made a little board to attach to the GPIO header of his Raspberry Pi and control up to 8 servos. The board is running a serial interface with a small microcontroller on board. There’s nothing in the way of schematics or code, a testament for why you should always use a good email address when sending something into the HaD tip line. It seems [Mikael] is making a proper board, and we’ll more than happily give it a full post when it’s complete.

Sending A Raspberry Pi To 130,000 Feet

July 18, 2012 by Brian Benchoff 23 Comments

We knew this wouldn’t take long. [David] sent a high altitude balloon into the upper atmosphere last weekend using a Raspberry Pi as the brains of the payload.

[David]’s payload consisted of a Raspberry Pi, natch, with a Logitech webcam, GPS receiver, and six AA batteries wired into a LDO regulator with a monstrous heat sink to keep everything in the EPX foam enclosure relatively warm in the frigid rarefied air of near space.

A high altitude balloon isn’t much fun without some real-time data coming down from the upper atmosphere, so [David] used a Radiometrix NTX2 transmitter module (anyone know of an equivalent part for the USA?) that transmits a measly 10 milliwatts. Even though the transmitter has an ‘official’ range of 500 meters, [David] got word of image data being received in Northern Ireland, over 500 km away.

We’re pretty impressed with [David]’s flight – and the fact that his flight is now 12th place on the list of UK balloon altitude records – but now we’re wondering what could be done with another Raspi flight to near space. [David] had a lot of computing horsepower up there, enough to get images from a webcam and send them down to earth. Now we’re wondering what else could be done with a Raspberry Pi in space.

You can check out the GoPro video of the very fast decent after the break, or check out the received images on [David]’s Flickr.

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