Here’s a good app note from Maxim on writing real-time clock code to get a stable system operation.
With the use of proper device initialization and code sequencing, accurate timekeeping and clock alarm operations become a more manageable task.
App note: Water and condensation safe touch sensing with the NXP capacitive touch sensors
App note (PDF) from NXP on water and condensation resistant capacitive touch sensors.
This application note explains the unique auto-calibration feature of the touch sensor family from NXP and provides guidelines for enhanced water and condensation safe operation, focusing on applications with capacitive touch buttons.
Recommended usage of Microchip serial RTCC devices
Another good app note from Microchip, a guidance in using the Microchip RTCC family of devices (PDF):
This application note provides assistance and
guidance in using the Microchip RTCC family of
devices. This application note covers both the I
2C™
(MCP794XX) and SPI (MCP795XXX) family of
devices. These recommendations are not meant as
requirements, however, their adoption will lead to a
more robust overall design. The following topics are
discussed:
• Basic Design Considerations
•VCC Supply
• Backup Supply options
• Input Pins
• Output Pins
• Crystal Selection
• Recommended Schematics (Appendix B-D)
Simple link budget estimation and performance measurements of Microchip sub-GHz radio modules
Assessing the link budget with this app note (PDF) from Microchip:
This application note describes a simple link budget
analysis, measurement and techniques to evaluate the
range and performance of wireless transmission with
results, and uses developed models to estimate the
path loss for short range Microchip Sub-GHz modules
using MRF89XA and MRF49XA radios both for indoor
and outdoor environment. Hence, an attempt is made
to provide designers with an initial estimate on wireless
communication system’s performance. The
performance parameters include range, path loss,
receiver sensitivity and Bit Error Rate (BER)/Packet
Error Rate (PER) parameters which are critical in any
communication.
Garage door signal hacking using RTL-SDR and TI Chronos watch
Students Ido Livneh and Gil Freidlin from Tel Aviv University have been experimenting with garage door opener signals using the TI Chronos watch and RTL-SDR dongle. Their technique involves using the SDR along with HDSDR software to acquire and record the signal, which is then analyzed using Python based tools and encoded for loading onto the Chronos RF wristwatch.
The project report is available as a 23 page PDF download.
Via RTL-SDR.com.
Arduino based waveform generator
Hemal Chevli made this Arduino based waveform generator. He wrote a post on his blog detailing its assembly:
Finally, after sitting in the TODO list for a long time, I’ve made a basic wavefrom generator based on arduino, made using this instructable as reference. I had an enclosure laying around which has incorrect dimensions for the project in which it was supposed to be used. The instructable had the sch for Waveform generator shield, I modified it a bit so its a stand alone system. I had to carefully plan the layout as it uses too many resistors, The DAC is done using R-2R network of 10k and 20k, in place of 20K I used two 10k in series. the output of DAC network goes to LM386 audio amp. Below are some build and testing pictures. It can generate 4different types of waves, sine, pulse,sawtooth and triangle, with frequency and amplitude control, and pulse width control for the pulse wave form. For each wave the corresponding LED lights up.
Check out the video after the break. Continue reading “Arduino based waveform generator”
Naze32 on Mini quad setup quadcopter
Oscar Liang wrote a post on his blog detailing how to setup a Naze32 Flight contoroller on his mini quad:
I have finally decided to swap out the KK2.1.5 with the Naze32 on my FPV250 mini quad. I have to say IMHO after a couple of test flight, the Naze32 Flight controller does perform better than the KK2.1.5, in this case. It doesn’t wobble as much when descents, and in high wind. It feels very locked in even in self level mode (horizon mode), unlike the KK2 it shows little but annoying vibrations in this mode. More importantly, I like working with the multiwii, which allows me to connect the FC to my phone through Bluetooth, so I can change the settings (PID and so on) a lot easier.
NSA XKeyscore tool targets Linux users
Apparently the US NSA believes that users of Linux in general, and readers of online ezine Linux Journal in particluar are extremists. According to this article on the NDR.de Panorama blog, internet users whose searches contained terms related to the TAILs (The Amnesic Incognito Live System) software program or Linux Journal had their internet traffic flagged for further scrutiny.
The investigation discloses the following:
Two servers in Germany – in Berlin and Nuremberg – are under surveillance by the NSA.
Merely searching the web for the privacy-enhancing software tools outlined in the XKeyscore rules causes the NSA to mark and track the IP address of the person doing the search. Not only are German privacy software users tracked, but the source code shows that privacy software users worldwide are tracked by the NSA.Among the NSA’s targets is the Tor network funded primarily by the US government to aid democracy advocates in authoritarian states.
The XKeyscore rules reveal that the NSA tracks all connections to a server that hosts part of an anonymous email service at the MIT Computer Science and Artificial Intelligence Laboratory (CSAIL) in Cambridge, Massachusetts. It also records details about visits to a popular internet journal for Linux operating system users called “the Linux Journal – the Original Magazine of the Linux Community”, and calls it an “extremist forum”.
The source code portion containing the XKeyscore rules can be downloaded from NDR.de.
[Happy Independence Day to our readers celebrating what little is left of liberty, freedom and justice in the USA.]
Free PCB coupon via Facebook to 2 random commenters
Every Friday we giveaway 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:
- Free PCB Sunday. The classic. Every week, get free PCBs right here on the blog comments
- Tweet-a-PCB Tuesday. Follow us and get boards in 144 characters or less
- Facebook PCB Friday. Free PCBs while you wait for the weekend
- Check out our video on how we mail PCBs worldwide.
Continue reading “Free PCB coupon via Facebook to 2 random commenters”
Week in (p)review July 04, 2014
Here’s a summary of major developments over the last week. Free PCB Friday is coming up soon.
- Bus Pirate v3.8 free PCB build
- Check out Geir Andersen’s solder paste dispenser, and Diogoc’s Hakko T12 soldering controller in the project log forum
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
Bus Pirate v3.8 free PCB build
Iñigo built a 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.
Video: Retrocomputing and machines that made the Net
CircleCitycon 2014 was held in Indianapolis, Indiana in June, 2014. Pete Friedman gave this presentation on the Unix and Unix-like systems that formed the early internet, and how they can provide interesting historical and technical perspectives for the modern hacker.
Remotely flash a weather station with a custom MSP430F5529 bootloader
Tml over at the 430h forum writes:
This project is fully functional and I use it to remotely reflash my weather station. I just push the new application image onto the web server, then the application working on the target device downloads it, parses and puts onto the flash and then lets the bootloader to the rest.
Via 43oh.
DIY 3D printer project
Nerdipedia documented a 3D printer build, called Huey:
This is not a general purpose 3D printer. It is the size of a small chest freezer and has a expected build volume over 200 litres. It uses eight drive motors and may require a lot of setting up compared to printrbot or similar.
The parts are mostly printed on my printrbot.
Unlike most repraps Huey has a stationary bed. Therefor the printhead must move in X,Y and Z dimensions.
Provided motors have enough motor torque and power this should scale up to be even larger.
You can find the build log here.
Check out the video after the break.
OpenBuilds Open Source Embroidery machine
sausagePaws over at OpenBuilds shared his open source embroidery machine project:
A simple Embroidery machine using an XY belt and pinion drive to drive a hoop under a standard sewing machine. Needle timing, machine power and stepper control are all provided by a PIC processor. A tablet provides the higher level formatting required for communicating with the PIC chip.
Via Open Electronics.
Check out the video after the break. Continue reading “OpenBuilds Open Source Embroidery machine”
Simple xtal oven for accurate clocks
From the comments on our earlier HP 5350B OCXO repair post, a temperature controlled OCXO xtal oven:
This is a very simple and easy to make temperature controller and heater to be attached to a xtal (crystal). The xtal is normally used to clock a microcontroller (PIC or ATMEL etc).
Normally xtals provide an accurate clock to 50 or 100 PPM (parts per million) making them useful for real-time clocks, like in your wristwatch. However their frequency output changes with temperature.This circuit keeps the xtal at a constant temperature – commonly called a “xtal oven” also called an “Oven Controlled Xtal Oscillator” or “OCXO”. Hence the xtal error is reduced to 1 – 10 PPM and the clock will keep almost perfect time.
This circuit can be built with very common cheap parts and means you don’t have to find or buy an expensive xtal oven.
Coupled with my 1-sec PIC timer algorithm HERE you can use ANY value of xtal to build a very high accuracy clock.
Via the comments. Thanks Nerd Ralph!
RFID reader for BuildBrighton door pt II
Chris Holden has written an article on their new door entry system at BuildBrighton:
The basic idea is this:
- A keyfob is presented to the reader and the serial number read from it.
- The keyfob number is displayed on the character LCD.
- This is sent (via the ethernet module) to a URL to validate the serial number and the web site returns data to say who the key belongs to
- If data is successfully received from the website, it is stored in the local eeprom chip
- If there is a fault and no data can be received from the ‘net, the eeprom is searched, looking for a matching keyfob number. If a match is found in eeprom, the data is read out and handled as if it had just come from the website.
- If the keyfob belongs to a valid user, their name is displayed on the character LCD and a relay is activated to open the door.
- If the serial number is not recognised, a “not recognised” message is displayed in the lower part of the LCD display.
Check out the video after the break.
XMega series: Clock system
Shawon Shahryiar’s second post of the XMega series is about the clock system, he writes:
There are several clock sources that XMega micros can use as clock. These are both internal and external clock sources. As stated earlier, clocks are not set by fuse settings unlike traditional Mega AVRs, they are controlled by software and the outputs from these sources can be multiplied using the internal Phase Locked-Loop (PLL). Thus there’s a wide range of clocks available in the XMega and it’ll not be needed to shut down and reprogram the XMega just to change its clock – a great relief from meddling with fuse settings. Some port pins can also output the system clock frequency. Literally there’s no need to depend on external quartz crystals which are not available in all frequencies.
Via Embedded Lab.
HP 5350B OCXO repair
Kerry Wong fixed his HP 5350B OCXO. He documented the whole process on his blog:
Last time, I did a teardown of an HP 5350B microwave counter. And as I mentioned in my teardown, the oven-controlled crystal oscillator (OCXO) did not appear to be working as the OVEN indicator would not go off even after hours of use but the counter appeared fully functional otherwise. So I decided to disassemble the crystal oven and see if this problem can be fixed.
Find an HP 5350B microwave counter teardown here.
DIY solder paste dispenser
Geir Andersen over at LetsMakeRobots has designed and built this cool solder paste dispenser:
As I’m doing SMD prototypes I wanted to do reflow soldering instead of hand soldering and needed a solder paste dispenser.
The professional ones are not that expensive but you need an air compressor and I was trying to avoid that extra cost and noise. So I came up with this design.
It uses a PICAXE M14 microcontroller and ULN2003 Darlington driver to run the 28BYJ-48 stepper motor. As a stepper the 28BYJ-48 sucks with its gear ratio, but for this purpose it is cheap and has lot of torque. For my type of work and one-off prototypes it works great.
Via the forum.
Check out the video after the break.