Puretus has been working on a high resolution capacitance meter:
One day I was looking for methods to measure capacitances of cap components. Even though it is pretty trivial now with my new Brymen multimeter, I ran into this design by Roman Black which turned out to be very well explained and in terms of learning this looks an interesting project to build. I was hoping that Roman would have included source code for the PIC16F628.
Bob writes:
I found an old EEPROM chip in my spare parts collection, the 93LC46B. The data sheet says it communicates using 3-wire serial I/O, and can store 1024 bits organized either as 8- or 16-bit words.
Next was the question of how to wire the bus pirate to the chip. I liked the idea of plugging some headers into a breadboard
These give the Bus Pirate’s clips something to grab onto.
Then, I wasn’t sure if I needed to create a separate power supply. Turns out one can simply power the chip directly from the Bus Pirate’s 3.3V connector. This is undoubtedly one of the reasons the Bus Pirate is such a well-regarded tool.
Get your own handy Bus Pirate for $30, including world-wide shipping. Also available from our friendly distributors.
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”
Here’s a summary of major developments over the last week. Free PCB Friday is coming up soon.
Coming up:
Recently the forum is flooded with people that are experiencing troubles with the Buspirate v3.6. Pieter in the forum was no exception. He first tried the Buspirate on his Windows 8.1 and Vista machine and went to the forum after finding out hise buspirate didn’t respond to anything. The supportteam in the forum suspected the PIC was not programmed or counterfeit FTDI chips were used. In the mean time Pieter tried the buspirate on more different machines and was dazzled it did work on a Crunchbang (Debian flavour) workstation. He investigated it further and tracked the error down to the latest FTDI driver (2.08.30), after de-installing and installing an earlier version of the driver (2.08.28) (scroll down to find the older version).
More info about the process on his blog and please report if this also works for you.
John Boxall over at Tronixstuff has a series of Arduino tutorials. This chapter fifty-five of a series will show you how to use the SIM900 GSM modules with Arduino:
The goal of this tutorial is to illustrate various methods of interaction between an Arduino Uno (or compatible) and the GSM cellular network using a SIM900 GSM shield, with which you can then use your existing knowledge to build upon those methods.
We’ll be using a SIMCOM SIM900 GSM module shield. (If you’re looking for tutorials on the Spreadtrum SM5100 modules, start here). There must be scores of Arduino shields or modules using the SIM900, so as you can imagine each one may be a little bit different with regards to the hardware side of things – so we’re assuming you have an understanding of how hardware and software serial works as well as supply voltages and the hardware side of the Arduino world.
Ian Johnston wrote a post on his blog detailing his bench power supply build:
My workshop has a couple of bench power supply’s, one is an old Farnell TOPS 3D 3-rail tracking job, and the other is a 3-rail CSI CSI3005XIII with Constant Current functions. The farnell is all analogue but has no constant current control, it has current limiting only. The CSI is good but doesn’t allow you to preset the constant current setting and thats what I want. So, rather than buy another PSU I thought i’d design and build my own, something thats directly suited for me and my projects.
Franci has written this tutorial describing the process used to convert a mouse into an Arduino web cam. In addition to the Arduino, all you need are an Ethernet shield, an optical mouse with ADNS-5020 sensor and a 10K ohm resistor. “An optical mouse uses a small camera that records the surface to calculate movements of the mouse. In this tutorial I will show you how to display the video signal of this camera in your browser. The mouse I took apart was an old Logitech RX 250 which contains ADNS-5020 optical sensor. This sensor records 15×15 pixel images in grayscale. It also calculates X-Y movements of the mouse.”
Via the contact form.
Boris Landoni from Open Electronics has designed and built another Christmas project the Spherebot, an open-source robot to draw on spherical objects:
Let’s create a plotter to decorate Christmas Tree balls with writing and drawings.
This machine: a printer, or better to say a plotter, which will draw with a marker on spheres at will, derived from models transformed into G-code files. The machine is easily doable with a few 3D printable pieces (we’ll provide the relative models in a special Thingiverse page) and a control board which is the same of the 3Drag. A computer will be needed for the appropriate printing software.
Rupert Hirst writes, “After the success using the Midas MCOB21605G1V 1602 OLED display in my previous article. My next challenge would be connecting the module to my i2C backpack custom PCB, Using the PCF8574 i2c IC”
Davide Gironi has posted a DS1307 library for AVR Atmega:
The DS1307 serial real-time clock (RTC) is a low-power, full binary-coded decimal (BCD) clock/calendar.
This library set and get year, month, day, hour, minute and second from this RTC.
Setup parameters are stored in file ds1307.h
This library was developed on Eclipse, built with avr-gcc on Atmega8 @ 1MHz.
Chirag Nagpal writes:
I have created a laser pointer cotrolled through a PC mouse using an arduino and two servo motors. For getting the position of the mouse on the screen I’m running a small python script on the PC that uses the xlib library to get the current position of the mouse . This is then sent to the arduino over the USB, to control the servos. The full documentation is on my website
Via the contact form.
The App Inventor group at MIT have unveiled App Inventor2. You may be familiar with the App Inventor project when it was previously featured. (At that time it was known as Google App Inventor.) Essentially it helps you build Android apps using a graphical interface which is useful for quick coding and debugging, and is especially helpful to new developers unfamiliar with coding.
Those familiar with the original app inventor will find a number of important changes including that App Inventor is now entirely in the browser. Previously to run App Inventor you needed to install and run a Java file called the Blocks Editor. Now, the Blocks Editor is just a different mode in your project that is viewed from the browser. Also all blocks are available on the left side. There is no longer a need to switch between Built-In, My Blocks, and Advanced drawers. The source code file is now a “.aia” file instead of a “.zip” file
For complete information on using App Inventor2 visit the project’s MIT homepage.
Telford Dorr shared a tutorial on how to apply a precision voltage to the AtMega Aref pin without accidentally blowing up the processor.
There’s a better way: feed the Aref pin resistor with an op-amp, and connect the op-amp negative feedback input directly to Aref. The op-amp will generate whatever output voltage is needed (within its limits, of course) to keep its negative input pin the same as its positive input pin (tied to a stable reference voltage), and thus, the Aref voltage the same as the stable reference.
Via the contact form.
Tom of Numato Lab writes:
We made a failed attempt to design and build a FPGA development board with DDR SDRAM last year. But this year we tried again and successfully built and tested a Spartan 6 FPGA board with DDR SDRAM. This board was built using KiCad and other open source tools. And best of all, this design is 100% open source as well.
More details about the board and links to downloadable design files at Numato.cc
Kerry writes:
In part 1 of this series of blog postings, I showed my preliminary design of a dual tracking linear power supply. In part 2, I showed the completed design and also the finished power supply circuits. And as promised last time, I have made a couple of videos showing the measurements of a few key parameters and will share the results here.
While you don’t hear quite as much as you did a few years ago about Asterisk, the free, open source framework for building communications applications, there’s still an active community developing and extending the code. The software essentially allows you to run your own VOIP Private Branch Exchange (PBX) on your home computer.
The crew at Raspberry Asterisk has developed a project which allows Asterisk to run on the Raspberry Pi using their custom firmware known as RasPBX. Their website also has links to modified versions of this code which provide BeagleBone Black support and additional features including “Preconfigured VoIP trunks, Flite text-to-speech engine as well as Google’s TTS and STT interfaces, free CallerID Name lookups for incoming calls, Voice Dialing with speech-to-text (STT) capability as well as Speed Dials, Yahoo News and Weather reports with text-to-speech (TTS) translation of the Yahoo news feeds, Telephone Reminders and Hotel-Style Wakeup Calls.”
For program details and download links, visit Raspberry-Asterisk.
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:
Some stuff:
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.
Michael Rubitschka writes:
Today I received a Agiltent 34461A Truevolt multimeter from Xtest.at the Austrian Agilent distributor.
I plan to write some articles about this multimeter and especially about features which imho separates it from it’s competition.
I am a Hewlett Packard / Agilent fan but I will try hard to be as unbiased as possible,…
A very interesting feature for me is the histogram display. I enjoyed the online demo’s about this feature and after unpacking the meter I had to try this feature immediately.
Raj just finished his mini LED Christmas tree project:
My two and a half year old son loves toys with flashing lights. For this Christmas I thought of making a mini LED Christmas tree for him. This project uses 22 multi-color LEDs which are driven by a PIC12F683 microcontroller using the Charlieplexing technique. The details of the build procedure is described in the following sections.
