JUL29
Decoding 4x4 keypad with AVR and 74C922
Keypad decoding or scanning using microcontroller is, lets face it - nothing new. The thing is that sometimes it can be a real pain when smaller microcontroller with not enough I/O pins is being used or when microcontroller has some more important task to do besides scanning the keypad.
Anyway, here is a project that scans 4x4 keypad using Atmel's 4+4 I/O pins (the usual method) and by using a special IC designed for that purpose: MM74C922. This IC is directly connected to keypad rows and columns with it's 4+4=8 pins, and on it's 4 digital output BCD pins it provides information about which key is pressed on keypad. Along with those 4 data pins it also has IRQ pin that can generate interrupt in microcontroller when key press is detected. Keypad scanning has never been easier!
Source: nevdull
JUL28
Compact fluorescent lamp schematics
Fluorescent lamps are very popular during these green days, even our Electra is giving them away for free after paying the electric bill.
They usually come in these color temperatures: Warm white (2700K), Cool white (4000K) and Daylight (6000K). Apart from those cheap fluo lamps that you can buy, there are also more expensive, branded ones. On this page, there is a big collection of most popupar (if not all) fluorescent lamps: Bigluz, Isotronic, Luxtek, Maway, Maxilux, Polaris, BrownieX, Philips Ecotone, Ikea, Osram Dulux El, Osram Dulux El, Eurolite and Sinecan 5, so fixing one does make sense when you can easily figure out what's wrong with it!
Source: Pavouk
JUL24
Adding RDS decoder to 1957' vintage radio
FM radio receivers usually don't have RDS decoder, but what about tube radio from year 1957?
This project is actually RDS decoder that is realised using TDA7330B RDS demodulator and ATtiny2313 microcontroller. Received and decoded RDS text is displayed on 2x16 HD44780 based LCD display with many options: displaying RDS time, displaying TA (traffic announcements) flag and scrolling 64 characters long RDS text. Here you can see integration of this RDS receiver into vintage tube radio receiver from year 1957.
Read on to see photos, how integration is accomplished and how to find discriminator output of your tube radio receiver.
Source: Edo Lelic
JUL23
Ceiling fan POV display
Just as we think we have seen enough of these POV displays, someone gets an idea of placing one on his ceiling fan.
This display is made out of 32 LEDs for each propeller's blade (5 in total) which means that some kind of multiplexing is used to connect those 160 LEDs to microcontroller. In this case, 8-bit shift registers 74HC595 that transform serial-in data into parallel-out data were used, and microcontroller is Atmel on Arduino platform. The good thing about this POV is that ceiling fan does not produce any noise as motors in every other POV display we have seen so far.
Source: UncleBone
JUL22
Automatic safe cracker
After finding an old safe with mysterious contents somewhere in the garbage, he tried opening it by listening to clicks (probably with a stethoscope) that dials supposably make, but with no luck at all. As manual brute force cracking is out of the question since it would take forever, he decided to build a machine to do it for him.
Author of this project connected servo motor to PC via Pololu servo controller and Arduino board. This safe cracking machine is attached to safe with some strong rare earth magnets. Safe's dial rotation is controlled via PC and servo is fitted with gears to enable at least two full dial's revolutions with only 180 degrees that classic servo can accomplish.
Source: Carlitos Contraptions
JUL16
Plasma ball with nixie tube
We have already seen what nixie tubes are commonly used for and in that case all digits in nixie must be functional. In this case it is not important to have a fully working nixie tube, but the glass casing must still be in one piece. The tube will be used for pretty unusual purpose - plasma ball.
Plasma ball is nothing else than a glass sphere (or any other shaped glass container) filled with low pressure gas equipped with electrode in the middle. For operation, high voltage high frequency signal is supplied to electrode and plasma filaments extend from it to the outer glass insulator. As a power source, Tesla coil can be used or as in this project a modified neon lamp driver.
Source: David Gustafik
JUL15
Nixie tube propeller clock
Although manufactured more than 30 years ago, nixie tubes are more popular than ever. Nixie tube is an electronic device for displaying mostly numbers and for its operation some 170 V is required. In the tube itself one can find set of numbers (cathodes) that glow with bright orange color because of the gas inside the tube. These days, these tubes are mostly used to build clocks because of it's unique non-boring retro look.
In this project a single-tube clock is made, but with a twist - POV is used to show all digits of clock at the same time. This is the same idea as in rotating POV LED display but instead of LEDs nixie tubes are used. Regardless of the fact that nixie tubes are extremely old technology, we all must agree that nixie tubes are one of nicest electronic components out there!
Source: Peter Csaszar
JUL14
Hacking wireless doorbell with brute force
Wireless doorbells are very popular today because of their easy setup and pretty low price. The only flaw is that we know all about how they operate. Frequency is 433.92 MHz and they use primitive signal encoding. Check out these extensive wireless doorbell reviews: top rated wireless doorbells.
Here we can see a device that consists of a 433.92 MHz transmitter module and a microcontroller that emulates pressing a button on bell's remote controller. The thing is that this "remote" is universal and it triggers every doorbell in range within a few seconds. Method used is brute-force that sends out all 2^12 or 4096 codes that original HT12-E produces. Now the only question is whether you are going to use this device to annoy all of your neighbourhood or to open their garage doors.
Source: Furrtek
