Fluke/Philips PM66xx frequency counter OCXO upgrade

Posted on Thursday, May 5th, 2016 in open source by DP | No Comments


Dan Watson documented on his blog an OCXO upgrade board he designed for the Fluke/Philips PM66xx line of frequency counters:

My counter came with the standard XO timebase option, which has fairly poor specs for stability and drift. It is difficult to trim precisely with the single-turn trimmer capacitor on the board. For most testing in my lab I use an external reference from a GPSDO, but it is still nice to have an accurate timebase available in the counter if I need to take it somewhere and do testing away from the bench.
Previously I posted about an OCXO upgrade I made for my Racal-Dana 1992. The fun of designing a similar upgrade for the Philips counter was one of my motivations for purchasing it. My upgrade board is roughly equivalent to the original PM9691 OCXO module, and it should be compatible with any Fluke/Philips counter that is capable of using that option.

More details at The Sync Channel blog.  Project files available at Github.

Developing an IR remote and Software controller

Posted on Thursday, May 5th, 2016 in Arduino, DIY, infrared by DP | No Comments


Hardware Hacks has published a new build, a DIY Infrared remote for speaker:

The idea is simple, we capture the IR signal from a remaining speaker remote and record the commands that get transmitted. We did this by connecting up our IR Receiver to the Arduino, the receiver has 3 pins and from left to right GND, +5V, SIGNAL and using the Arduino IRRemote library. Run the Examples > IRRemote > IRrecvDumpv2 example. (see image below with the IR Receiver connected to a Arduino Uno (for prototyping, you can use the Arduino nano, but you’ll have to upload/reset the sketches when testing) If this is running correctly, point the speaker remote at the receiver and press a button – When the IRReceiver gets any data it will flash with the on board red LED, so you know it’s working. Open the Arduino serial monitor and you should see an output of the data it has received.

Project info at Hardware Hacks site.

Via the contact form.

Lockitron Bolt teardown

Posted on Wednesday, May 4th, 2016 in Teardowns by DP | No Comments

The crew from Fictiv wrote in to let us know about their special edition teardown video of Lockitron Bolt, which includes insights from the co-founder on material decisions, engineering insights, prototype development, and lots more.

More details at Fictiv blog.

Via the contact form.

#FreePCB via Twitter to 2 random RTs

Posted on Tuesday, May 3rd, 2016 in Free PCBs by DP | No Comments


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.

Philips T8 LED tube teardown

Posted on Tuesday, May 3rd, 2016 in Teardowns by DP | No Comments

In a previous post Electronupdate did a teardown of a 48″ T8 Cree LED tube, this time a 48″ T8 Philips LED tube.


3V3/30V DC/DC converter using SN6505A

Posted on Tuesday, May 3rd, 2016 in Chips, DIY by DP | No Comments


Robert Gawron made a 3V3/30V DC/DC converter using SN6505A:

Recently I’v got my samples of SN6505A, it’s a really nice IC, so I decided to make a simple DC/DC converter to get familiar with it. What I like in this chip is that it can operate on input voltage as low as 2,5V – that makes it great for battery devices. It’s also nice, that it’s a very minimalist design – on primary side all what is needed is decoupling capacitor. One disadvantage is that it doesn’t have a feedback loop.
To increase efficiency, SN6505A can operate with more developed versions of transformers, but I used the simplest configuration – one coil on each side.

Project info at Robert Gawron’s blog.

HOW-TO: Add live websites to GIT without interruptions or security risks

Posted on Tuesday, May 3rd, 2016 in #liveupdates, how-to, site by Ian | 3 Comments


Over at the DEV site we’ve been using GIT repositories hosted at to push (deploy) changes to the live server instantly. It’s way slicker than uploading changed files by FTP, which has no roll back if something goes wrong. It also solves one of our China internet problems: routing to Bitbucket is much more reliable than to our servers in Germany.

It is finally time to merge the DEV site with the main Dangerous Prototypes sites – the blog got a new theme yesterday. When we started updating the rest of the site it seemed much easier and safer to put it in GIT too. There are a lot of tutorials about deploying websites with GIT, but none completely covered the process to safely put existing websites into GIT with no interruptions and maximum security.

Updating folder structure

We’re starting off with a legacy folder structure rooted in early cloud services and personal ignorance. The web root is at /var/www/. Other parts of the site (/forum, /docs) sit in subfolders of the root:


Using a Bus Pirate to connect to a Raspberry Pi

Posted on Tuesday, May 3rd, 2016 in Bus Pirate, how-to, R-Pi by DP | No Comments


Scott Dixon describes on his website how he used the Bus Pirate to connect to a Raspberry Pi:

The other day I found myself with a Rasberry Pi that I wanted to use but I had forgotten my FTDI UART cable. What I did have is my Bus Pirate v3.6 and I found it was pretty easy to use it’s transpartent UART bridge macro to connect to the Pi.

More details at 0x20 homepage.

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

Simple crystal tester

Posted on Monday, May 2nd, 2016 in RF, testing by DP | No Comments


Dilshan Jayakody writes:

This is simple Colpitts oscillator to test commonly available passive crystals which range between 2MHz to 27MHz. This unit must connect to an oscilloscope and/or frequency counter to get the frequency of the crystal.
This circuit is design to work around 9V to 12V DC power source. Both 2SC930 transistors can replace with any high speed NPN transistor such as 2SC829, 2SC933, etc.

More details at Dilshan Jayakody’s blog.

Inside card sorters: 1920s data processing with punched cards and relays

Posted on Monday, May 2nd, 2016 in vintage by DP | No Comments


Ken Shirriff did an in-depth write-up of the punched card sorter:

Punched card sorters were a key part of data processing from 1890 until the 1970s, used for accounting, inventory, payroll and many other tasks. This article looks inside sorters, showing the fascinating electromechanical and vacuum tube circuits used for data processing in the pre-computer era and beyond.

More details at Ken Shirriff’s blog.

Check out the video after the break.


Free PCB Sunday: Pick your PCB

Posted on Sunday, May 1st, 2016 in Free PCBs by DP | 22 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:


App note: The 2-Channel serial audio interface: A tutorial

Posted on Sunday, May 1st, 2016 in app notes by DP | No Comments


A pretty older application note about the serial audio interface by Cirrus Logic. Link here (PDF)

It may come as a surprise to those trying to make their initial investigation into audio systems design that there is a de-facto standard for transferring audio data within a system. Despite the differing naming conventions used within the industry, these apparently different interfaces are essentially identical. For the sake of simplicity, we will use the term Serial Audio Interface (SAI) in this discussion. The Serial Audio Interface is by far the most common mechanism used to transfer two channels of audio data between devices within a system; for instance, from the analogto-digital converter to the Digital Signal Processor (DSP) and then the digital-to-analog converter.

App note: The LM4935 headset and push-button detection guide

Posted on Sunday, May 1st, 2016 in app notes by DP | 1 Comment


Another headset plug-in detection from Texas Instruments. Link here (PDF)

The headset detect circuitry can differentiate between mono, stereo, mono with microphone, and stereo with microphone headsets. It can operate while the LM4935 is placed into low current standby mode, which promotes extended battery life. In standby mode, it consumes no extra current, if the headset has not been inserted into the headset jack.

App note: Differences between ATmega328/P and ATmega328PB

Posted on Sunday, May 1st, 2016 in app notes by DP | No Comments


Differences between ATmega328/P and ATmega328PB (PDF!) application note from Atmel:

This application note assists the users of Atmel® ATmega328 variants to understand the differences and use Atmel ATmega328PB.
ATmega328PB is not a drop-in replacement for ATmega328 variants, but a new device. However, the functions are backward compatible with the existing ATmega328 functions. Existing code for these devices will work in the new devices without changing existing configuration or enabling new functions. The code that is available for your existing ATmega328 variants will continue to work on the new ATmega328PB device.
The ATmega328PB is the first 8-bit Atmel AVR® device to feature the successful Atmel QTouch® Peripheral Touch Controller (PTC).
For differences in errata, typical, and electrical characteristics between ATmega328 variants and ATmega328PB, refer to the specific device datasheets.

App note: MSP430 32-kHz crystal oscillators

Posted on Sunday, May 1st, 2016 in app notes by DP | No Comments


MSP430 32-kHz crystal oscillators (PDF!) application note from Texas Instruments:

Selection of the right crystal, correct load circuit, and proper board layout are important for a stable crystal oscillator. This application report summarizes crystal oscillator function and explains the parameters to select the correct crystal for MSP430
ultralow-power operation. In addition, hints and examples for correct board layout are given. The document also contains detailed information on the possible oscillator tests to ensure stable oscillator operation in mass production.

DIY 32ch FPV 5.8ghz LCD

Posted on Friday, April 29th, 2016 in, DIY by DP | No Comments


Spikey made his own DIY 32ch FPV 5.8ghz LCD with Dirty Board PCB’s:

If you’re like me, you don like buying stuff that’s ready-to-go, but rather build one yourself. We usually spend more money, but it’s way more satisfying I really didn’t want to buy an overly expensive FPV LCD receiver, so I made my own DIY 32ch FPV 5.8ghz LCD, that is compatible with EVERY transmitter on the market now.

More info at Spikey’s project page.

Teardown: A couple of laptop batteries (aftermarket vs original)

Posted on Thursday, April 28th, 2016 in Teardowns by DP | No Comments


Viktor writes:

 I’ve recently opened up a few laptop batteries and decided to take some pictures. Keep reading if you’ve ever wondered just how different the Chinese aftermarket batteries are compared to the originals.

More details at Karosium homepage.

Bus Pirate v3.8 free PCB build

Posted on Thursday, April 28th, 2016 in builds by DP | No Comments


@MegaLabs08 tweeted picture of his free Bus Pirate v3.8 PCB build. 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.

Building a 32K RAM Board

Posted on Thursday, April 28th, 2016 in DIY by DP | No Comments


Glitch has posted details on his build of a RAM board for the Challenger III:

With a quantity of 495 prototype boards in hand, it was time to build up a RAM board for the Challenger III. My implementation uses a single 32K x 8 static RAM in DIP packaging, which is split up into eight 4K segments, each of which can be enabled or disabled individually. It’s also expandable to 64K and beyond due to a few design decisions.

Project info at Glitch Works homepage.

Raspberry Pi web server using flask to control GPIOs

Posted on Wednesday, April 27th, 2016 in R-Pi, tutorials by DP | No Comments


Rui Santos from Random Nerd Tutorials writes:

In this project you’ll create a standalone web server with a Raspberry Pi that can toggle two LEDs. You can replace those LEDs with any output (like a relay or a transistor).
In order to create the web server you will be using a Python microframework called Flask.

More details at Random Nerd Tutorials homepage.

Check out the video after the break.


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Recent Comments

  • ian: No, that's exactly how it should be :) Sorry about missing names on comments, the theme is being reworked as we speak.
  • J. Peterson: Nice writeup. It looks like some of the formatting for your command examples needs some missing newlines?
  • Geert Jordaens: I'm not sure what kind of licensing I have to add since it is a fairly straight forward implementation of the adaptive Huffman Decoding. For...
  • erich: For anyone interested, I've added some c++ code for adaptive huffman decoding in the git repository.
  • Sjaak: I would add some more protection in the used trigger file (on the serverpilot site) then not using a standard name :) hopefully they use...