Improving DCF77 reception over longer distances
While working on their open source hardware Nixie Tube Clock, guys over at the Electronics-Lab.com are also working on DCF77 time synchronization part.
The DCF77 transmitter is located in Germany (Frankfurt) and they are trying to receive the signal from a distance of more than 1500 km away. They did some interesting testing with different antenna sizes and posted their results online: "It seems that antenna selection affects received signal quality, bigger length and better tunning plays significant role in reception in long distances form DCF transmitter. So if you plan to use a DCF receiver on long distances, look for a better antenna."
Source: Electronics-Lab.com Blog
3-axis accelerometer with MMA7361L and PIC
If you are looking for a 3-axis accelerometer IC for your next project, take look at the Freescale MMA7361L. It is very simple to use by connecting it to ADC input of your favorite microcontroller and reading analog values which represent value of currently applied G-force.
Here is a very nice looking evaluation board that is built around PIC16F887 microcontroller. It connects to USB for power and has an LED display for all three axes.
Be sure to check out the video of this board in action.
Source: Viktors DIY
If you have a habit of misplacing your keys you might want to consider building this Bluetooth enabled key finding keychain.
It is based on low power consumption MSP430 microcontroller from Texas Instruments and a Bluetooth module. It has a rechargeable Li-Ion battery inside with a dedicated charging IC. The BT module is made to be always discoverable and after connecting to it the keychain starts to beep. Then you can look for your keys by listening to the buzzer. There is also a mobile application for the phone that should be used to connect to the keychain.
Now all you need to do is make sure you don't lose your phone.
Source: Kernel Hacks
Turntable Photography Equipment - published
A friend asked me if I could build him a device that would allow him to take photos of his products in 360 degrees.
That kind of photo is actually an animation that consists of several photos of the same product but from different angles. It means that we need a device that can be controllable and that could take pictures on even intervals.
How Reed Switches are Made
Reed switch has two contacts which are usually normally open and when it gets affected by nearby magnetic field the contacts close and make a closed circuit. Reed switch can also be used to make a relay. This is done by adding a wire coil around the reed switch. When coil is energized it creates a magnetic field which causes reed switch to close (or open).
Be sure to check the video of reed switch manufacturing!
Time manipulator DCF77
This is not actually a time manipulator, but it is a DCF77 signal spoofer that is used to manipulate time on DCF77 synchronized clocks. DCF77 is a system that works on low frequencies and it constantly transmits real time clock information over 77.5kHz at 50kW from Frankfurt am Main.
So, here is a device that will "overwrite" the original DCF77 signal and force all clocks around it to synchronize to custom preset time and date. It has ~6W transmitter and is based on ATmega16.
You can see this device in operation in video after the break.
Source: Matthias Franz, HB9EFY
Mini 4-channel Logic Analyzer with Atmega8
This is a mini Logic Analyzer that can be used to "look" at logic levels of digital signal for analysis purposes. For example, it can be used to analyze digital signals coming out of various sensors, IR receivers or communication ICs.
It is built around Atmega8 AVR microcontroller, has 4 input channels and can capture signals of up to 400kHz. Data is displayed on Nokia 3310 LCD (84x48 pixels) with backlight. Take look at the presentation video after the break.
Schematics and source-code are published on the project page.
Source: Vassilis Serasidis
GSM Phone Jammer Circuit Schematics
Here is a very simple plan to make a "dirty transmitter" that is also known as Cell Phone Jammer.
It is based on NE555 as simple noise-maker whose output is fed to a single transistor oscillator. The oscillator is designed to operate between 800MHz and 2GHz which happens to be the frequency span used for GSM phones. The frequency of operation is set with a trim-capacitor.
The battery should last no longer than 1 hour and the range of jamming is around 10-15 feet.
Source: Laszlo Kirschner