## Art of Computer Programming, Volume 4A, The: Combinatorial Algorithms, Part 1 By Donald E. Knuth

Knuth’s multivolume analysis of algorithms is widely recognized as the definitive description of classical computer science. The first three volumes of this work have long comprised a unique and invaluable resource in programming theory and practice. Scientists have marveled at the beauty and elegance of Knuth’s analysis, while practicing programmers have successfully applied his “cookbook” solutions to their day-to-day problems. Knuth, Volume n has been published, where n = 4A.

We don’t stock this, but may later.

Filed under: announce — by adafruit, posted January 14, 2011 at 4:38 pm

## Using an AdaFruit OLED display on a Boarduino without a level shifter

AdaFruit released a monochrome OLED screen last week and I wanted to test it with a netduino. So, I ported the Arduino driver written by Limor to C#, wrote a basic test app, soldered header pins to the OLED display, hooked it up to my netduino  and… nothing happened. It became clear that I needed to test the OLED display on an Arduino first to make sure that the screen was not defective in the first place. I had on hand a Boarduino that I had previously upgraded with an Atmega328 and hacked to run on 3.3 volts instead of 5 volts, removing the need to use the level-shifter provided with the OLED display.

These displays are small, only about 1″ diameter, but very readable due to the high contrast of an OLED display. This display is made of 128×64 individual white OLED pixels, each one is turned on or off by the controller chip. Because the display makes its own light, no backlight is required. This reduces the power required to run the OLED and is why the display has such high contrast; we really like this miniature display for its crispness!

The driver chip, SSD1306 can communicate in multiple ways including I2C, SPI and 8-bit parallel. We prefer SPI since its the most flexible and uses a small number of I/O pins so our example code and wiring diagram will use that.

The OLED and driver require a 3.3V power supply and 3.3V logic levels for communication. The power requirements depend a little on how much of the display is lit but on average the display uses about 20mA from the 3.3V supply. Built into the OLED driver is a simple switch-cap charge pump that turns 3.3v-5v into a high voltage drive for the OLEDs. You can run the entire display off of one 3.3V supply or use 3.3V for the chip power and up to 4.5V for the OLED charge pump or 3.3V for the chip power and a 7-9V supply directly into the OLED high voltage pin.

You’ll need a level shifter to communicate with this OLED using a 5V microcontroller such as an Arduino, but we include a DIP level shifter chip!

We have a detailed tutorial and example code in the form of an Arduino library for text and graphics. You’ll need a microcontroller with more than 1K of RAM since the display must be buffered.
You can download our SSD1306 OLED display Arduino library from github which comes with example code. The library can print text, bitmaps, pixels, rectangles, circles and lines. It uses 1K of RAM since it needs to buffer the entire display but its very fast! The code is simple to adapt to any other microcontroller.

Filed under: leds-lcds — by adafruit, posted at 11:04 am

## BASIC Interpreter for Homebrew Z80 Computer

A follow up to a previous post about GG’s Homebrew Z80 Computer. He’s implemented a BASIC interpreter using the AM9511 math processor. Oh, and did I mention the whole thing fits into 3Kb of ROM? He writes:

Hi, I finally wrote a Basic interpreter language for my Z80/AM95 8-bit NANO COMPUTER in order to easily program it.
I called it “8BASIC” because everything must clearly fit the 8 digit LED display.

The video shows all commands and statements, plus two famous benchmarks vs. contemporaneous 1970′s-80′s computers.
Due to the strong mathematical support of the AM9511 math processor, the BASIC interpreter runs reasonably fast for a 2.5 MHz machine, offering seven significant digits floating-point arithmetic.

Very impressive!

Filed under: EE — by johngineer, posted at 10:03 am

## INDUSTRIAL SAFETY VIDEO

Phil just got the stitches out of his thumb after a mishap with some robotic research. We’re considering having the entire Adafruit staff review this video (above) “Safety isn’t always easy”. Warning, this video is the most messed up thing you’ll ever see. Starts slow, then it’s all Cronenberg.

Filed under: random — by adafruit, posted at 10:03 am

## OH YAH, It’s part finder FRIDAY!

The DS1307 is an easy to use real time clock, goes great with the 32khz crystal we mentioned last week. Add a 3V coin cell to the battery pin and this chip will keep track of the date and time for many years. You know it, you use it, you love it – the part finder.

Filed under: EE,maker business — Tags: , — by adafruit, posted at 12:00 am

## Robot HAL suit

1:40 – “Do you feel the power?”…

Filed under: robotics — by adafruit, posted January 13, 2011 at 4:59 pm

## Pixar’s Zoetrope

Pixar’s Zoetrope, fun stuff.

Filed under: art — by adafruit, posted at 4:08 pm

## Hacked Kinect video scratching

Hacked Kinect video scratching via Bruce.

Filed under: art,kinect hacking — by adafruit, posted at 12:36 pm

## Mail bag!

IT CAME FROM THE MAIL BAG!

I just wanted to drop a line and say that I really like what you’re doing with the site. I have been using kits from your store to learn about micro-controllers, and I’ve found the tutorials on ladyada.net very helpful. Thank you for the help and support! – Russell.

Filed under: announce,mail bag — by adafruit, posted at 12:24 pm

## Engineer/Programmer Needed for Prototype Temperature/RH Data

New job posted on the Adafruit job boards! Engineer/Programmer Needed for Prototype Temperature/RH Data….

Objective: To provide cost effective real time display and logging of temperature and relative humidity in multiple vivaria as well as to log this data for other display purposes.
Project Requirements:

Basic: – A combined temperature and humidity probe that has a very small footprint, is protected from excess moisture, and has a long (10ft+) cable from the probe itself to the controller – Controller displayed readings of temperature and humidity based on probe number – Computer displayed readings of temperature and humidity based on probe number as well as the ability to log the data and make calculations from it (e.x. 24 hour high and low temp/RH, daily averages, weekly averages, etc) -The ability to connect 4 or more probes to the controller

Advanced: – The ability to turn on and off a device (e.x. a fan) based on probe readings – Based on temperature readings, have an audible alarm/tweet/e-mail notification/SMS message sent – The ability to access data via the internet (e.x. while on vacation or at work)

Filed under: announce — by adafruit, posted at 12:16 pm

## PCB stencils on the cheap (kinda)

PCB stencils on the cheap (kinda). ShareBrained writes -

I have these Avery mailing labels that I use to address Chronulator kit shipments to my customers. They’re made of paper, and they stick to stuff. What if I cut my stencil from a mailing label? Let’s give it a try…

To start with, I need to prepare a solder paste template. I output a PDF with the paste layers shrunk a bit. I shrink the paste layer because the mailing label is quite thick, and therefore so is the paste when it’s applied. So I need to compensate for the thick paste by making the paste areas smaller.

From the paste template file, I laser the mailing label with the Epilog 45W laser at work. My settings are “speed 25″ and “power 25″. I use raster mode, as it tends to produce more accurate, even results.

Filed under: EE — by adafruit, posted at 12:14 pm

## Light-up cereal boxes

Light-up cereal boxes. It’s hard to resist these…

Its fabulous packaging uses induction power to create, among lots of other things, some of the most amazing cereal boxes we’ve ever seen, which can illuminate in stages to create an eye-catching effect.

But it’s not just eye-candy either, because the technology can also be used to power toys and other items to give a battery-free demonstration. The company also had a pack of Energiser batteries that were being charged on its magical induction shelf, ready for you to buy and use straight away.

Filed under: random — by adafruit, posted at 12:11 pm

## Friday Night Drawbot

Spotted in the Adafruits flickr pool: this clever take on the MAKE Drawbot using a DC Boarduino. Pete (aka Raster) writes:

Friday night turned into Robotics/Art night at the 2XL Makerspace. I remembered seeing this Drawbot Project, and while you can modify normal servos to be continuous rotation servos, I already had some continuous rotation servos on-hand, so we got to work. (Or play, if you prefer.)

The Drawbot consists of just a handful of parts. Here’s a list of the items we used:

All of these pieces are available from our friends at Adafruit Industries.

Check out the complete how-to here. Nice work, Pete!

Filed under: boarduino,project packs,robotics — by johngineer, posted at 10:42 am

## Batteries – A to Z of Electronics

Batteries – A to Z of Electronics… The history and technology in batteries by Jeri Elsworth. This is part of our A – Z electronics series, we are sponsoring these videos for Jeri to create, we love these!

Most of us became familiar with what batteries do when we were just small children with all our battery-operated toys. But the history of its invention is packed with drama and uncertainty.

Artifacts were discovered outside of Baghdad that resemble batteries. They consisted of a terracotta pot with a copper cylinder and an iron rod held in place with an insulator. Some believe if they were filled with fruit juices, they would produce a small current. The most intriguing part of the story is that it pre-dates the official invention of the battery by at least 1500 years. Currently, there’s no definitive way to determine what these were really used for.

In the late 1700s, Luigi Galvani, a professor of anatomy, was performing experiments on frogs, trying to prove their testicles were in their legs. He made the observation that their legs would twitch when touched by a statically charged scalpel. He spent the next ten years performing experiments, and found that touching unlike metals simultaneously across the legs would cause them to twitch. He concluded that there were three types electricity: friction, lightning, and his newly discovered animal electricities.

But not everyone agreed with them. Alessandro Volta, a professor of physics, a self-proclaimed genius, and a ladies’ man was convinced there was only one type of electricity. I want the frog legs. He started his own experiments, and quickly discovered that frog tissue was not the source of electricity, but a sensitive detector. He found that he could use salt water-soaked felt in place with the frog tissue and still produce electricity.

He believe that he discovered an unlimited source of electricity that came from the tension of two dissimilar metals, and the corrosion of the salt water was only an annoyance. Because of this belief, his primitive batteries, or voltaic piles, have extra plates on the top and bottom.

We now know that the current is generated by a process of oxidation and reduction. Oxidation occurs at the more reactive electrode, and reduction happens at the less reactive electrode. The electrode that’s being oxidized will be consumed, and positive ions will diffuse away from it. Depending on the chemistry of the cell, at the reduction electrodes, sometimes gas is formed, and other times, it’s plated, and negative ions diffuse away. Externally in the circuit, the electrons flow from the oxidation electrode to the reduction electrode.

This is the electrical symbol for a battery. The small line is the negative terminal. See the resemblance?

This is a partial list of the activity series of metals, lithium being the most active, and gold being the least. The more active a metal, the more likely it will lose electrons and oxidize. To the right, you can see the standard oxidation potential in volts. In a perfect world, you can use these numbers to calculate out the voltage of your cell, depending on the electrodes you choose. If we chose zinc and copper, the difference would be about one volt.

You can create your own voltaic cell at home very easily with two dissimilar pieces of metal and a piece of paper soaked in vinegar. The bottom plate is a piece of copper. I’m not exactly sure what the washer is made of. When I test with the volt meter, I can see that it’s 0.8 volts.

We can tell that the washer is the anode, because the volt meter will indicate with a negative sign if the leads are hooked up backwards. Cells like this have a disadvantage, because they continue to react, even when current isn’t flowing.

An improved cell would have electrodes surrounded by a solution that only reacts when current is flowing. This can be achieved by using a salt bridge with a permeable membrane that allows ions to pass. Rechargeable batteries are very similar to one time use batteries. The difference is, the chemistry can be reversed, restoring the electolytes and the electrodes.

Lead acid is an example of this type of battery. During discharge, the electrodes are turned from lead and lead oxide to lead sulfate, and during charging, it’s returned back to lead and lead oxide and sulfuric acid.

You can increase the voltage of a battery by adding more cells stacked in series. I’ll demonstrate this by hooking 40 9-volt batteries together.

Oops. I’d better get some bigger electrodes.

If you need to increase current, you can put batteries in parallel. This is effectively making their plates a larger surface area.

Here I’m shorting a fine wire across the leads of the 9-volt battery. Not much happening. Now we see smoke when I hook two batteries in parallel, and short the lead. And with three batteries, it’s far too much current for such a small wire, and it immediately melts.

Well, I hope you liked the video about batteries. I had a great time putting it together, and I want to think my sponsors at Adafruit Industries. It’s their concept for this. Be sure to drop them a note and let them know that you like this, and better yet, buy something from them. You might check out their MintyBoost, which is a boost converter so you can charge USB devices from double A batteries.

You can always reach me at scorched.chips@gmail.com. I love hearing from you guys. Send me your suggestions.

## Arduino breadboard labels

I own three BoArduino, but I keep semi-permanently installing them in some project or the other – I guess that happens to most people? So here’s a little label, you can print out, stick on to a Atmega and it will show you the pin out that match the Arduino standard.

I don’t claim to be the first one to think this idea. I think I saw it here first

I tried printing it – but the font was a bit too light – and it needed something special. So I made my own from scratch.

I’ll just let the photos do the rest of the talking….but before I do, here’s the files. PDF, Illustrator. Oh, and a SVG that should work in Inkscape – it’s opensource

Filed under: arduino — by adafruit, posted at 12:16 pm

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