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.
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.
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:
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.
Over at the DEV site we’ve been using GIT repositories hosted at BitBucket.org 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:
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.
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.
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.
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:
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.
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.
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.
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.
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.
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.
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.
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.