Monthly Archives: June 2015

EAGLE BOM generation script

via Dangerous Prototypes

bom-gen_001

Dilshan Jayakody writes:

This is a quick post about EAGLE parts list generation script which I was written to replace existing “part2html.ulp”. This script generates more organized and detailed BOM HTML file and it can directly replace “part2html.ulp”.

This script is tested with EAGLE 6.6.0, but it can also work with older versions of EAGLE software.
This script is available to download at github with usage details.

New products: RoboClaw 2x5A, 2x15A, and 2x30A motor controllers (V5)

via Pololu Blog

We’re now selling the latest V5 versions of the RoboClaw 2x5A, 2x15A, and 2x30A dual motor controllers from Ion Motion Control. Like the previous V4 RoboClaws, they can drive a pair of brushed DC motors at voltages from 6 V to 34 V, but the 2x5A now has a USB serial interface (in addition to TTL serial, RC, and analog inputs) like its larger siblings, and the 2x15A and 2x30A have a new heat sink design that should improve cooling. We expect to have updated documentation for the new versions soon.

Ion Motion Control RoboClaw 2×5A dual motor controller (V5).
Ion Motion Control RoboClaw 2×15A or 2×30A dual motor controller (V5).

Gates to FPGAs: TTL Electrical Properties

via Hackaday » hardware

On the path to exploring complex logic, let’s discuss the electrical properties that digital logic signals are comprised of. While there are many types of digital signals, here we are talking about the more common voltage based single-ended signals and not the dual-conductor based differential signals.

Simulated "Real Life"
Single-ended Logic Signal

I think of most logic as being in one of two major divisions as far as the technology used for today’s logic: Bipolar and CMOS. Bipolar is characterized by use of (non-insulated gate) transistors and most often associated with Transistor Transistor Logic (TTL) based logic levels. As CMOS technology came of age and got faster and became able to drive higher currents it began to augment or offer an alternative to bipolar logic families. This is especially true as power supply voltages dropped and the need for low power increased. We will talk more about CMOS in the next installment.

TTL rtl dtl

TTL was a result of a natural progression from the earlier Resistor Transistor Logic (RTL) and Diode Transistor Logic (DTL) technologies and the standards used by early TTL became the standard for a multitude of logic families to follow.

TTL Signal Voltage

When connecting two logic gates together there are essentially four voltages of interest: the high and low voltage that the gate’s output will produce, and the high and low voltage that the gate’s input is expecting.
Image2

TTL Output signal voltage specification:
Voltage Output High VOH 2.4V
Voltage Output Low VOL .4-.5V
TTL Input signal voltage specification:
Voltage Input High VIH 2V
Voltage Input Low VIL .8V

In short the output gate generates a slightly larger signal than required by the input gate; the difference between the output and input voltages allows for some loss of signal and/or the addition of some noise into the equation. This difference is often referred to as the noise margin.

TTL Voltage Compatibility

The TTL signal levels are usually the same, or very close for both “standard” 5 volt TTL and for low voltage 3.3 volt TTL, often referred to as LVTTL. While this would sound like they should then be able to connect together safely there is however a specification for most TTL/Bipolar logic families that states that the input signal cannot exceed the power supply by more than a few tenths of volts.  There is a  possibility that a 5 volt gate may generate more than 3.3 volts on its output, hence the problem.

3.3V TTL Feeding 5V TTL 5V TTL feeding 3.3v TTL

There are logic families such as 74AHCT that are tolerant of higher voltages than their power supply on their inputs, however this is a CMOS family and will be discussed in the next post.

Schottky Logic

Before I do a quick summary of the Bipolar/TTL families let me first explain what a “Schottky” family logic device is and where it gets its speed improvement from.

A transistor when used as a switch can go into a state known as saturation. Part of the definition of “transistor saturation” includes the state when both Base-Emitter and Base-Collector junctions are forward biased, however the property of interest here is that it is also slow to turn off as there is an excess of charge built up that has to be drained off first before the device starts to respond. A Schottky diode across the base-collector junction effectively holds the transistor right on the edge of being turned “on” and keeps excessive charge from building up. A transistor paired with a Schottky diode in a gate is often redrawn as shown above on the right.

TTL Logic Families

74 Original TTL – Some parts still around.
74LS Low Power Schottky – Good compromise speed vs power/noise and inexpensive.
74S Schottky – The sledge hammer of the early TTL, speedy but a heavy lift.
74AS Advanced Schottky – When you really to go really fast.
74ALS Advanced Low Power Schottky – Fast and low power, however not without noise considerations due to the speed in which the signal changes (slew rate).
74F Fairchild Advanced Schottky TTL – Fast and low power, a little less noisy than ALS in my experience.
74L Low Power – Not widely used.
74H High Speed – An early compromise for more speed, not widely used.

Here you can see the bipolar TTL based families. Some of the families above are also able to sink and source a lot of current which we will also compare to their CMOS counterparts in the future.

Glitch Quiz

Lastly if you remember the last post which covered Basic Logic, I asked about a risk of a glitch in the circuit shown below on the left. The glitch would arise when “D” changes state because in theory there is a time when one equation, known as a term, has stopped being true before the other term has become true. In fact the D signal itself is not needed as the two sets of terms were otherwise identical

example1-resized example2

Looking at the circuit on the right; have we gotten rid of the possibility of the glitch since the terms are no longer otherwise equal?


Filed under: Featured, hardware, slider

#FreePCB via Twitter to 2 random RTs

via Dangerous Prototypes

KHOS-2-3-4-5-6P Every Tuesday we give away two coupons for the free PCB drawer via Twitter. This post was announced on Twitter, and in 24 hours we’ll send coupon codes to two random retweeters. Don’t forget there’s free PCBs three times a every week:

  • Hate Twitter and Facebook? Free PCB Sunday is the classic PCB giveaway. Catch it every Sunday, right here on the blog
  • Tweet-a-PCB Tuesday. Follow us and get boards in 144 characters or less
  • Facebook PCB Friday. Free PCBs will be your friend for the weekend

Some stuff:

  • Yes, we’ll mail it anywhere in the world!
  • Check out how we mail PCBs worldwide video.
  • We’ll contact you via Twitter with a coupon code for the PCB drawer.
  • Limit one PCB per address per month please.
  • Like everything else on this site, PCBs are offered without warranty.

We try to stagger free PCB posts so every time zone has a chance to participate, but the best way to see it first is to subscribe to the RSS feed, follow us on Twitter, or like us on Facebook.

Naturebytes wildlife cam kit

via Raspberry Pi

Liz: The wildlife cam kit has landed. If you’re a regular reader you’ll know we’ve been following the Naturebytes team’s work with great interest; we think there’s massive potential for bringing nature to life for kids and for adults with a bit of smart computing. Digital making for nature is here.

Naturebytes is a tiny organisation, but it’s made up of people whose work you’ll recognise if you follow Raspberry Pi projects closely; they’ve worked with bodies like the Horniman Museum, who have corals to examine; and with the Zoological Society of London (ZSL). Pis watching for rhino poachers in Kenya? Pis monitoring penguins in Antarctica? People on the Naturebytes team have worked on those projects, and have a huge amount of experience in wildlife observation with the Pi. They’ve also worked closely with educators and with kids on this Kickstarter offering, making sure that what they’re doing fits perfectly with what nature-lovers want. 

Today’s guest post is from Naturebytes’ Alasdair Davies. Good luck with the Kickstarter, folks: we’re incredibly excited about the potential of what you’re doing, and we think lots of other people will be too.

We made it! (quite literally). Two years after first being supported by the Raspberry Pi Foundation’s Education Fund and the awesome folk over at Nesta, we finally pressed the big red button and went into orbit by launching the Naturebytes Wildlife Cam Kit – now available via Kickstarter.
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This is the kit that will fuel our digital making for nature vision – a community of Raspberry Pi enthusiasts using the Pi to help monitor, count, and conserve wildlife; and have a hell of a lot of fun learning how to code and hack their cam kits to do so much more – yes, you can even set it up to take chicken selfies.

We’ve designed it for a wide range of audiences, whether you’re a beginner, an educator, or a grandma who just wants to capture photos of the bird species in the garden and share them with her grandchildren – there’s something for everyone.

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This was the final push for the small team of three over at Naturebytes HQ. A few badgers, 2,323 coffees, 24 foxes,  and a Real Time Clock later, we signed off the prototype cam kit last week, and are proud of what we’ve achieved thanks to the support of the Raspberry Pi Foundation that assisted us in getting there.

We also get the very privileged opportunity of appearing in this follow-up guest blog, and my, how things have changed since our first appearance back in September 2014. We thought we’d take you on a quick tour to show you what we’ve changed on the kit since then, and to share the lessons learnt during our R&D, before ending with a look at some of the creative activities people have suggested the kit be used for. Suggest your own in the comments, and please do share our Kickstarter far and wide so we can get the kits into the hands of as many people as possible.

Then and now – the case.

Our earlier prototype was slick and thin, with a perspex back. Once we exposed it to the savages of British weather, we soon had to lock down the hatches and toughen up the hinges to create the version you see today. The bird feeder arm was also reinforced and a clip on mechanism added for easy removal – just one of the lessons learnt when trialing and testing.

The final cam kit case:

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The final cam kit features:

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Schools and Resources

A great deal of our development time has focused on the creation of a useful website back end and resource packs for teacher and educators. For Naturebytes to be a success we knew from the start that we’d need to support teachers wishing to deliver activities, and it’s paramount to us that we get this right. In doing so, we tagged along with the Foundation’s Picademy to understand the needs of teachers and to create resources that will be both helpful and accessible.

Print your own

We’ve always wanted to make it as easy as possible for experienced digital makers to join in, so the necessary 3D print files will now be released as open source assets. For those with their own Pi, Pi cam and custom components, we’ve created a developer’s kit too that contains everything you need to finish a printed version of the cam kit (note – it won’t be waterproof if you 3D print it yourself).

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You can get the Developer’s Kit on Kickstarter.

The Experience

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Help us develop a fantastic experience for Naturebytes users. We hope to make a GUI and customised Raspbian OS to help users get the most from the cam kit.

It’s not much fun if you can’t share your wildlife sightings with others, so we’re looking at how to build an experience on the Pi itself. It will most likely be in the form of a Python GUI that boots at startup with a modified Raspbian OS to theme up the desktop. Our end goal is the creation of what we are calling “Fantastic Fox” – a simple-to-use Raspbian OS with pre-loaded software and activities together with a simple interface to submit your photos etc. This will be a community-driven build, so if you want to help with its, development please contact us and we’ll get you on board.

Creative activities

This is where the community aspect of Naturebytes comes into play. As everyone’s starting with the same wildlife cam kit, whether you get the full complete kit from us or print your own, there are a number of activities to get you started. Here are just a few of the ones we love:

Participate in an official challenge

We’ll be hosting challenges for the whole community. Join us on a hedgehog hunt (photo hunt!) together with hundreds of others, and upload your sightings for the entire community to see. There will be hacking challenges to see who can keep their cams powered the longest, and even case modification design competitions too.

Identify another school’s species (from around the globe!)

Hook up a WiFi connection and you’ll be able to share your photos on the internet. This means that a school in Washington DC could pair up with a school in Rochdale and swap their photos once a day. An exciting opportunity to connect to other schools globally, and discover wildlife that you thought you may never encounter by peeking into the garden of school a long way away.

Build a better home (for wildlife)

It’s not just digital making that you can get your hands into. Why not build a garden residence for the species that you most want to attract, and use the camera to monitor if they moved in (or just visited to inspect)? A great family project, fuelled by the excitement of discovering that someone, or something, liked what you build for them.

Stamp the weather on it

There’s an official Raspberry Pi weather station that we love – in fact, we were one of the early beta testers and have always wanted to incorporate it into Naturebytes. A great activity would be connecting to the weather station to receive a snapshot of data and stamping that on to the JPEG of the photo your camera just created. Then you’ll have an accurate weather reading together with your photo!

Time-lapse a pond, tree or wild space

It’s fantastic to look through a year’s worth of photographic data within 60 seconds. Why not take a look at the species visiting your pond, tree or a wild space near you by setting up a time-lapse and comparing it with other Naturebytes users near you?

We’d love to hear your ideas for collaborative projects – please leave a note in the comments if you’ve got something to add!

 

The post Naturebytes wildlife cam kit appeared first on Raspberry Pi.

DIY laser diode driver | Constant current source

via Dangerous Prototypes

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GreatScottLab’s instructable on how to make your own constant current source and how to get a ‘burning’ laser diode:

In this project I will show you how I extracted a laser diode from a DVD Burner which should have the power to ignite a match. In order to power the diode correctly I will also demonstrate how I build a constant current source which delivers a precise and steady current to the load.

Check out the video after the break.