#FreePCB via Twitter to 2 random RTs

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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.

E-Paper clock in a Sick of Beige case

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Kevin Rye built this E-Paper clock and wrote a detailed explanation on his blog describing the build:

I still have to put the finishing touches on the code. Instead of having the display constantly update, I’d like to set an alarm on the DS3231 RTC to go off once a minute, and only update the display on alarm. Hopefully I’ll save some battery power that way. As of now, the battery only lasts a couple of days.   I built in a USB battery charger to make it easier to charge it.   I got my PCBs in from OSHPark and put it all together in an 80mm x 80mm Sick of Beige case. Check it out!

Via the forum.

Sick of Beige project case is available at Seeed for $3.

Open electroencephalography


Michael Paul Coder obtained his first printed circuit board from Olimex and started with the OpenEEG project years ago, but only recently started dabbling in the measurement of brain waves while dreaming. He’s managed to build a device which can comfortably record brainwaves during sleep. He’s taken that a step further and established the Lucid Scribe Database (LSDBase), a place for documenting the effects of lucidity on dreams. Anyone with a device compatible with the OpenEEG project can now upload to the Lucid Scribe Database project. (Source code for the OpenEEG plugin is available on GitHub.)

I designed a headband with a motion detector that is sensitive enough to pick up the heartbeat and can easily detect rapid eye movements. And I wrote a program that records my sleep and plays an audio track when it detects that I am dreaming. I can sometimes hear the songs in my dreams and act on that knowledge – by flying, for example.

The software he uses is known as Lucid Scribe.

There are volumes of information regarding the hardware, software and techniques utilized in this project available at LSDBase. A very interesting project.

A DIY vacuum fluorescent display driver

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Kerry Wong posted an update on his vacuum fluorescent display driver we covered earlier:

As I mentioned before, there are many driver chips (e.g. MAX6921, MAX6931) readily available for interfacing with VFDs. The driver circuit I am showing here is a bit more complex as it uses only the generic 74HC’s and discrete transistors.

The basic technique for driving a multiplexed VFD is very similar to that for driving a 7-segment LED display. The major difference is the voltage requirement for the control gates and segment. For a VFD, the driving voltage is typically between 20V and 30V instead of the TTL or CMOS logic level used for driving 7-segment LED displays. Thus we must employee some kind of voltage shifting circuitry to translate the logic level signal into the voltage required by the VFD.

ATtiny25 Basic VCO, RC oscillator overclocking and testing frequency pickup

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Alex over at InsideGadgets has posted an article describing how he built an ATtiny25 voltage controller oscillator (VCO):

I recently bought a Rigol DS1052E and have been playing around with the different functionality it has. Eventually I came to the point that I’d like to see what frequency does to various components and wanted to build a voltage controller oscillator (VCO).

Flipdot fun project

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Bertho shared his flipdot project in the forum:

For those of you who don’t know flipdots, these are mechanical discs (black/white or black/color) that flip with a (semi-)permanent magnet which can be polarized in either direction. A large current must be applied to a coil to flip the magnetic field and the disc will flip. Flipdots are available in 1×7 strips and in different sizes and colors. The direction of the current through the coil depends on which direction you want to flip. The current must be kept at 350mA for at least 450 micro seconds for the permanent magnet to reverse polarity.

Via the forum.

Check out the video after the break.

Continue reading “Flipdot fun project”

The Turbo Entabulator – a 3D-printable, fully mechanical computer

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Chris Fenton has released the files allowing you to build your own 3D printable mechanical computer.

This is is a simple, 3D-printable (caveat: It requires some springs, bearings, rubber bands, and nuts/bolts), fully-mechanical computer. It has 3, single-digit base-10 counters for memory, and processes a chain of 10-position punch cards. With the included program, it will compute the first few digits of the Fibonacci sequence.

You can find project details on Chris Fenton’s website.

App note: Protecting 1-wire 5V slaves from overvoltage

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Here is a tutorial from Maxim describing how to protect your 1-wire slave devices from overvoltage.

If an application requires writing to EPROM devices after deployment, 5V devices need to be protected from overvoltage exposure. This article explains how to have 1-Wire EPROMs and 5V 1-Wire devices on the same bus, if the 5V devices are protected from the programming pulse.

Free PCB Sunday: Pick your PCB

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We go through a lot of prototype PCBs, and end up with lots of extras that we’ll never use. Every Sunday we give away a few PCBs from one of our past or future projects, or a related prototype. Our PCBs are made through Seeed Studio’s Fusion board service.

This week two random commenters will get a coupon code for the free PCB drawer tomorrow morning. Pick your own PCB.

You get unlimited free PCBs now – finish one and we’ll send you another!

Don’t forget there’s free PCBs three times every week:

Continue reading “Free PCB Sunday: Pick your PCB”

How to ID your Arduino board


Which Arduino boards are commonly in use and how do you distinguish one from another? Alex Castle has posted a roundup of the most common Arduino boards on the market right now, with tips on how to distinguish between them based on processing capabilities, feature sets and form factor. This summary should be helpful to those new to the Arduino scene. You can find Alex’s post at Tested.com.

App note: LLC DC DC reference design using dsPIC

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Here is a LLC DC DC converter reference design from Microchip using dsPIC digital signal processing capabilities for control.

As presented in this application note, resonant converters, LLC resonant converters in  particular, have all of the features mentioned above, resulting in a compact and highly efficient design. Their ability to keep the output voltage regulated, over a very wide input voltage range, contributes to reducing the overall system cost. The relatively simple architecture of these parts permits the implementation of control and supervision/management tasks with a small pin count dsPIC DSC from Microchip. Sophisticated control is possible, using the DSP capabilities of dsPIC DSC devices.

App note: Damage from a lightning bolt or a spark—It depends on how tall you are!

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Here’s an application note from Maxim describing how to protect printed circuit boards (PCBs) against ESD destruction:

Large steel buildings, automobiles, mountains, even people survive real atmospheric lightning. Humans can also create their own miniature lightning bolts (sparks) and survive. When those sparks reach an IC, however, major trouble results. In this tutorial, we will discuss ways to protect printed circuit boards (PCBs) against ESD destruction. We will show that analog parts with bigger geometries are the best to use to protect a field-programmable gate array (FPGA) with their small geometries. By taking these measures, the ICs in an FPGA remain more reliable and deliver consistent quality performance.

A similar version of this article appeared in the July 27, 2012 issue of Power Electronics Technology magazine

Online source lets you send and receive Enigma cipher comms


The Enigma machine was a World War II era encryption device used by the German army. It was the subject of substantial efforts by Allied cryptographers which finally resulted in the successful cracking of the code, which led to decryption of German military comms.

We found this website which allows you to encode and decode messages using an online version of the Enigma encryption engine. It’s sponsored by the Enigma World Code Group.

While the Enigma World site does not deal with the technical specifics of how the machine worked, you’ll want to check out their links page for other sites covering the technical aspects, including a link to a C++ library for simulating the Enigma machine.

App note: Modular-exponentiation timing with MAXQ30 microcontrollers

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Here is an article from Maxim on modular exponentiation, modular arithmetic accelerator (MAA) and lists typical times to execute various sized exponentiations:

The MAXQ1050, MAXQ1850, and MAXQ1103 are secure 32-bit microcontrollers that provide hardware support for performing modular arithmetic. This is done using an engine called the modular arithmetic accelerator (MAA). This application note gives typical execution times for various modulus sizes, key types, and optimization levels.

Universal digital timer based on MSP430

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SUF shared his new project the universal digital timer based on MSP430 in the project log forum:

I have an oven and a deep fryer at home. Both has the same type of digital timer in it. The timer has a two digit 7 segment display and two buttons with one drawback. It only beep when the time elapsed but unable to switch of the device.
I realized that I need a timer like this for various purposes with switching capability.
Here are the planed usage:

– Control the deep fryer above
– Small, desktop timer (it may requires LCD instead of LED display because of the battery operation)
– Control my (planed) UV lightbox what will used for PCB solder mask developing
– Soldering station watchdog

Turn a smart phone into a signal generator

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Jacob Beningo has written an article detailing how to turn a smart phone into a signal generator:

Signal generators are a handy thing to have around the lab. They are perfect for testing inputs on a new hardware design and verifying the behavior of a circuit before connecting all the pieces together. In recent years these lab tools have not only decreased in size but also in cost. The result has been a plethora of portable versions that now exist on the market.

For an engineer-on-the-go, this is very convenient but often times having to bring one more piece of equipment always seems to put the tool bag over the 50 pound limit. This is one reason why it is becoming popular to design lab equipment that can be plugged into a smart phone. Rather than carry around another device with a computer in it, utilizing the computing power and capabilities of the phone allows the device to be smaller, cheaper and weigh less!

Free PCB coupon via Facebook to 2 random commenters

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Every Friday we give away some extra PCBs via Facebook. This post was announced on Facebook, and on Monday we’ll send coupon codes to two random commenters. More PCBs via Twitter on Tuesday and the blog every Sunday.

Don’t forget there’s free PCBs three times every week:

Continue reading “Free PCB coupon via Facebook to 2 random commenters”

Sony Open SmartWatch project


Sony’s SmartWatch is an Android compatible watch based on an ARM Cortex-M3 CPU, STM32F205RGY6, from STMicroelectronics and includes Bluetooth capability and a touchscreen. It retails for around $100.

Previously, developers could create apps for SmartWatch with the Sony Add-on SDK, but Sony is now opening up the project to allow hackers to create and flash alternative firmware, by sharing technical details and instructions. Sony calls it their Open SmartWatch Project and the webpage contains links to a wealth of documentation including instructions on how to flash firmware, a hacker guide with links to datasheets and peripheral information, and a backup download of the factory stock firmware just in case you need to restart from scratch.

Week in (p)review June 14, 2013

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Here’s a summary of major developments over the last week. Free PCB Friday is coming up soon.

Coming up:

  • Free PCBs via Facebook on Friday
  • App notes on the weekend
  • Free PCB Sunday
  • 3D model on Monday
  • Eagle parts and tips on Tuesday
  • Free PCBs via Twitter on Tuesday
  • A new tutorial on Wednesday
  • Workshop video on Thursday
  • Weekly roundup and preview every Friday