App note: Energy Harvesting reference design user’s guide

in app notes by DP | 0 comments


An application note from Silicon Labs on energy harvesting reference design user’s guide(PDF!):

The purpose of this reference design is to demonstrate an ultra low power wireless sensor, powered from an energy harvesting source. This application is typical of systems which wake periodically to measure and transmit results. Since it is powered from an energy harvesting source, no batteries need to be replaced for the life of the system (life expectancy is greater than 15 years or 7000 mA-H) and the wireless node can be designed with a very thin profile (battery height is 0.17 mm). The system consists of two components: a wireless Sensor node and an EZRadioPRO® USB Dongle. The Sensor Node uses a Silicon Labs Si1012 wireless MCU. The Dongle uses a Silicon Labs C8051F342 MCU and a Silicon Labs Si4431 radio.

DIY active differential probe characterization

in measurement, oscilloscope by DP | 0 comments


An 1GHz active differential probe project by Daniel Kramnik:

This project was an ultra high input impedance (0.5pF||30MΩ or better) high bandwidth differential oscilloscope probe designed, built, and revised over the course of two weekends for the 2014 MakeMIT hardware hackathon. It can be built for about $30 in parts, plus the cost of etching or sending out a PCB and (optionally) 3D printing a chassis. A list of downloads necessary to build a complete probe is available at the bottom of this page. The project was in the top 10 the first week, advancing the team to the second week, where it took second place.
The objective of the project was to provide hobbyists with an affordable means to make high speed measurements, in which respect I would call it a great success. I was able to use the probe to measure various data converter waveforms from my digital oscilloscope project that I had otherwise been unable to get good data on.

Free PCB coupon via Facebook to 2 random commenters

in Free PCBs by DP | 2 comments


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.  The coupon code usually go to Facebook ‘Other’ Messages Folder .  More PCBs via Twitter on Tuesday and the blog every Sunday.

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

Continue reading →

Posted in Free PCBs | Tagged | 2 Comments

Week in (p)review January 23, 2015

in week in review by DP | 0 comments


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
  • Free PCBs via Twitter on Tuesday
  • Weekly roundup and preview every Friday

DIY PSU console

in DIY, power supply by DP | 0 comments


Simon wrote a post on his blog detailing his DIY PSU console assembly:

If I was going to build a power supply display add on, I decided to add some current limiting to it as well – but it had to be simple, cheap, and work with the panel meters. Yes you can get similar Ammeters on eBay they are more suited to the 10A range, where I want to measure 10’s to 100’s of milliamps.
And seeing as I’m designing something, I thought I’d also add a feature that a lot of current limited (at least at the low end) miss – a method of adjusting the current limit *WITHOUT* having to short your rails.


Bus Pirate v3.8 free PCB build

in builds, Bus Pirate by DP | 0 comments


Tommi of Mikropure documents his experience building the free Bus Pirate v3.8 PCB. The Bus Pirate is an open source hacker multi-tool that talks to electronic stuff.

If you build a free PCB we’ll send you another one! Blog about it, post a picture on Flicker, whatever – we’ll send you a coupon code for the free PCB drawer.

Get your own handy Bus Pirate for $30, including world-wide shipping. Also available from our friendly distributors.


Audible frequency chirp sonar with the Stellaris Launchpad

in ARM, hacks by DP | 0 comments


Jason Bowling writes:

Over the last year I’ve been working towards an underwater sonar system for ROVs and surface boats. In order to learn the basic signal processing required to detect the echoes, I initially got a simple sonar working in air with a desktop conferencing USB speaker/mic running on Windows. A writeup, including source, is here. That article describes the algorithms used in detail and would be a good read if you want the details of how this works.
The next logical step seemed to be to get it working on a microcontroller. There are plenty of low cost ultrasonic sonar modules available that work really well in air, but the idea was to work towards getting a sonar that worked in water. There are currently no low cost sonar modules for hobby use in water.

Check out the video after the break.

Continue reading →

Electric imp-controlled 120VAC relay switcher

in DIY by DP | 0 comments


An  electric imp-controlled 120Vac relay switcher project by Dillon Nichols:

 I updated my old GitHub project, Elec-Imp-Relay, to include my new code for the web app and electric imp files. The main index.html page is very basic and uses Google’s Web Starter Kit as the basis. Lines 9-13 allow the web app to be added to the iPhone Home Screen as an app and includes the link to the image I created from a coffee cup and the electric imp logo. Line 13 includes a link to the project because I am hosting the web app from GitHub pages and I need to specify the location of this particular icon. I used Google’s style sheets for the app with slight modifications and they include code for all the possible functions.

The source code is available on Github.

#FreePCB via Twitter to 2 random RTs

in Free PCBs by DP | 0 comments

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.

Hacker Camp Shenzhen vol 4: 182 degrees open for registration!

140405-IMG_20140405_162505-W600 Hacker Camp Shenzhen volume 4: “182 degrees” is on! Join us from Thursday April 1 to Saturday April 3, 2015 for fun, food and 3 solid days of electronics tours in Shenzhen China and beyond.

Tickets are available now. Come to the world’s electronics capital and experience Shenzhen like a local hacker. Tour the famous Huaqiangbei electronics markets with people who live in the neighborhood, figure out what to eat and how to get around.

This camp we’re adding an oft requested factory tour! Take our own party bus to a few factories around Shenzhen. Exact factory visits will be determined by you! We’ll take requests and try to include something for everyone.

Saturday we’ll explore electronics and tools markets most foreigners could never find: Yihua and the massive Shajing.


  • Optional: Tuesday March 31 – Dinner at Szechuan place
  • Optional: Wednesday April 1 – Tour of Dongmen market & sign street, copy mall, early arrival dinner at Japanese Secret Location
  • Thursday April 2 – How to survive Shenzhen, Huaqianbei tour, hot pot dinner
  • Friday April 3 – Factory tours, BBQ dinner
  • Saturday April 4 – Tour of Yihua and Depu markets, Hacker shaokao

That’s just an overview. See the full Hacker Camp Shenzhen schedule here. You can expect nightly dinners and parties all week. Be sure to give yourself a few days to explore the market on your own after the camp!


Tickets for the camp cover bus rental, materials, meeting room, a translator, a set of PCBs, and 3 bottles of Tsing Tao (Ching Dao) per dinner. There’s only 20 tickets available and we expect they will sell out fast. Or maybe it’ll be a small intimate group. Who knows! We’re excited to see you there!

  • Student/Starving Artist ticket – $250
  • Normal ticket – $300
  • Supporter ticket – $400 (your name on the site and schedule of every future camp)

We also include allowance for Paypal fees, wire transfer fees, and currency conversion. Hacker Camp Shenzhen is a “no profit” event, meaning we’re lucky to break even.

Where to stay, visas, how to get there

City Inn is the recommended hotel, but be prepared for really bad internet and no WIFI. Check out the Hacker Camp mini-site and our Shenzhen survival guide. Be sure to get WeChat and join the Shenzhen Hacker group chat after you buy a ticket!

SIM card provided

We’re traveling to places an hour or so north of Shenzhen, there are no taxis and nobody speaks English. Everyone must have a working SIM card with data, and this camp we’ll provide them!

Can’t make this one?

Hacker Camp Shenzhen volume 5: “Pun TBD” will be in June 2015, just prior to Shenzhen Maker Faire.

Hacker Camp Shenzhen mailing list!

Don’t miss out, signup to be notified about upcoming hacker camps in Shenzhen!

USB interfacing for AVR microcontrollers

in AVR, USB by DP | 0 comments


Ralph Doncaster  writes:

Since the release of V-USB, dozens of projects have been made that allow an AVR to communicate over USB. USB data signals are supposed to be in the range of 2.8 to 3.6V, so there are two recommended ways to have an AVR output the correct voltage. One is to supply the AVR with 3.3V power, and the other is to use 5V power but clip the USB data signal using zener diodes. Most implementations of V-USB, like USBasp, use the zener diodes. I’ll explain why using a 3.3V supply should be the preferred method.

Free PCB Sunday: Pick your PCB

in Free PCBs by DP | 83 comments


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 →

Posted in Free PCBs | Tagged | 83 Comments

App note: EMI and ESD filtering of audio interconnects

in app notes by DP | 1 comment


App note(PDF) on NUF2441FC EMI and ESD filter chip from ON Semiconductor.

The continued ever-increasing integration of more functions into personal electronic devices such as cell phones has made electronics manufacturers demand more integrated functions to reduce part count and save board space. Cell phone manufacturers have also driven component manufacturers to produce more efficient parts to increase the battery life on cell phones. Quite often though this is done at the cost of added sensitivity to ESD. Concurrently, as data rates and clock speeds increase the need to filter Electromagnetic Interference (EMI) also needs to be resolved. The ON Semiconductor NUF2441FC was designed to provide both ESD protection and EMI filtering for headset and speaker phone lines in cell phones with low line losses. This dual function component reduces part count and significant board space in a Flip-Chip package offer excellent performance at a low cost.

App note: Analog switches solve many problems within a cell phone

in app notes by DP | 0 comments


Applications(PDF) of analog switches inside a cell phone by ON Semiconductor.

Analog switches have been available since the 60’s as a component for systems designers. With the advent of ASICs and ASSPs, many designers have not experienced the real value of these devices. Today’s designers may be familiar with the venerable MC14066, a workhorse that has been around for 30 years or more. The device consists of 4 independent switches that provide bilateral capabilities when “ON” and nearly infinite impedance when “OFF”.

Enter the single gate solution: On Semiconductor now offers a low voltage, single version of the 4066 in a one gate package. The MC74VHC1G66DFT2 is a single switch (SPST) occupying less than 4.5 mm 2 package, specified from 2.0-5.5 V and offers < 25 ohms resistance when turned “ON” and almost infinite impedance when turned off. Interestingly, the device can pass/stop either a digital or analog signal. Digital signals get passed with <1.0 ns delay, and very nearly no change in the signal. Analog signals get passed with less than 0.1% distortion and the device has a –3.0 dB point of >100 MHz. Several more devices were added to the portfolio including SPST, SPDT, dual SPST, DPDT, 2:1 Mux, dual DPDT functions. These are all available in tiny packages from 2.1 x 2.0 mm to 3.0 x 3.0 mm.

App note: Li-Ion/Polymer Shunt battery charger system with low battery disconnect

in app notes by DP | 2 comments


Li-Ion/Polymer Shunt battery charger system with low battery disconnect (PDF!) app note from Linear Technology:

The LTC®4071 allows simple charging of Li-Ion/Polymer batteries from very low current, intermittent or continuous charging sources. A near zero current low battery latching disconnect function protects even the lowest capacity batteries from deep discharge and potentially irreparable damage. The 550nA to 50mA operating current makes charging possible from previously unusable sources. With its low operating current the LTC4071 is well suited to charge low capacity Li Ion or thin film batteries in energy harvesting applications. The unique architecture of the LTC4071 allows for an extremely simple battery charger solution, requiring just one external resistor.

App note: 1-Wire communication with PIC microcontroller

in app notes by DP | 0 comments


An application note (PDF!) from Microchip on 1-Wire communication with PIC microcontroller:

This application note introduces the user to the 1-Wire® communication protocol and describes how a 1-Wire device can be interfaced to the PIC® microcontrollers.
1-Wire protocol is a registered trade mark of Maxim/Dallas Semiconductor.
A software stack for the basic, standard speed, 1-Wire master communication is provided with this application note along with an example application