Archive / May, 2013

Software Spectrum Analyzer Using a JeeNode


JeeNode user dzach put together an impressive software spectrum analyzer using the transceiver on the JeeNode:

Based on an idea that initiated in the JeeLab forums, a sample sketch and JeeLib, it provides a basic spectrum analyzer with a waterfall display along with normal frequency and time domain displays of the signals, as they are heard by the very same RFM12B module employed in the board.

Read more and get the code at the Jee Labs wiki.

By Shawn Wallace on May 23, 2013.

Talking to the Raspberry Pi’s Serial Console with a Modern Device BUB


A question popped up on the Raspberry Pi forum a little while back asking whether the BUB could be used to connect to the serial port on the Raspberry Pi’s GPIO header. The answer is yes; it works quite well! The BUB is essentially a breakout board for FTDI’s FT232 chip that translates between a USB connection and a TTL-style UART. This is the chip that was on the pre-Uno Arduino (USB translation is handled in software on a second microcontroller on the Arduino Uno). The BUB (and BUB II) are used to communicate with most Modern Device and Jee Lab controllers, except for the BBLeo.

The BUB has a few other features that make it a bit more flexible than Just Another Breakout Board. For example there’s a polyfuse to help protect your computer if you accidentally draw too much current, and a jumper to change logic levels from 3.3 to 5 volts. The BUB I also has a handy breakout area that allows you to reroute the signals to any of the pins on the header. This is useful for connecting to devices with different pinouts like the Raspberry Pi or Parallax Propeller.

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By Shawn Wallace on May 15, 2013.

New JeeLabs Blog Series: What If?


Well, it’s a relatively new series from our friends in the Netherlands that takes a more conjectural approach to learning about electronics. In Jean Claude’s words:

The what-if question is a great way to experiment, especially in electronics and electro-mechanics, because it lets you be prepared and avoid silly (and sometimes catastrophic) outcomes, such as a damaged component, a harmful burn, or even an explosion.

This approach lends itself to all sorts of practical questions:

  • What if I short out a 3x AA battery pack?
  • What if I connect my chip the wrong way around?
  • What if I have to use a 12V power supply instead of 5V?

But also issues as varied as:

  • What if I omit a certain component from my circuit?
  • What if I unplug the Raspberry Pi without shutting it down?
  • What if I wanted to use HouseMon in combination with MySQL?

Power considerations are often the most vexing part of working with electronics, and sure enough that’s where the series starts. The first few posts explore the questions “What if I mix 3.3V and 5V?” (Parts one, two, and three) and What if the supply (to an Atmega) is under 3.3V?“.

It’s a weekly series, so bookmark it, follow the RSS feed, or catch up on the wiki.

By Shawn Wallace on May 13, 2013.

The Othermill, a Desktop Milling Machine with Snap Fit Joints


Today Otherfab announced a Kickstarter for the Othermill, a unique desktop milling machine. The Othermill is an evolution of the MTM Snap milling machine developed by Otherfab’s Jonathan Ward over the past few years. Otherfab is a small group of engineers and designers within Otherlab, and Jonathan was formerly at the Center for Bits and Atoms. The Othermill comes out of the Fab Lab ecosystem, and is comparable to the Roland Modela in that paradigm.

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By Shawn Wallace on May 8, 2013.

New Product: Serial LED Strips


We bought some Serial LED strips for the shop and I am having a whole lot of fun programing them. Like most 12 volt strips they are wired with three LEDs in series, which are in turn controlled by one high-speed serial chip. So there are 50 control chips on a 5 meter strip. (The strips have 30 LEDs per meter). We looked for strips with 60 LEDs per meter but our supplier could not provide them without a sizable order from the factory.

The somewhat coarse grain of this control might be a show-stopper for some LED projects, but they’re well positioned for lots of general computer-controlled changeable color and display applications. I am having a whole lot of fun programming them. I found an excellent high-speed library here. The author hasn’t returned my email yet, I’ll call him Daniel G. from his email address, and give him more specific credit if I can get in touch, and he wants the attention.

Our LED strips are controlled with the UCS1903 chipset, which has, as one of its great virtues, the ability to control the LEDs with only a ground and data line. All of the Chip Select and Clock functions have been replaced in the chip, by careful timing control, which also requires a microController running at least 16 Mhz, so Lillypad owners are out of the picture, at least for now. The lack of clock signal lines creates a very clean interface. Two wires, Ground and +12 volts, go to the strips from the power supply, and two wires, GND and Data In, connect the microcontroller to the strips. The strip headers thoughtfully have two wires on ground (if you buy a whole 5 meter roll), so it’s a very easy hoookup. More strips can just have data and GND lines daisy chained, and power lines perhaps run in parallel, to avoid huge currents through the strips, although it might be possible to run 10 meters daisy chaining all four wires, especially if all the LEDs are not on at any one time.

Writing 255, 255, 255 to all LEDs yields a strip (5 meter) operating current of 2.3A (@ 12 volts). The total current divided by 150 (50 controller chips x 3 colors) yields about 15mA per LED so the strips should have a long lifetime at that current, since most superbright LEDs are usually rated at 20 mA or greater.

I cooked up five demo sketches to help users get going on using the library. There are some videos below (of uneven quality) showing the effects. There are some nasty flickers in some of them that just represent interference patterns between the video frequency and the update frequency of the LED’s. Needless to say, the LEDs don’t look like this to the human eye. Cyborgs though, will eventually be connoisseurs of visual phenomenon entirely invisible to people.

The Serial LED strips are in stock and in the shop here.

By Shawn Wallace on May 3, 2013.