Ajoy built a TV pattern generator for the Open 7400 Logic competition. Using 74C14 Shmitt inverters to generate various timing signals, he later combines them using a few NAND 74C00 gates to get a B&W TV video signal generator by CCIR-B standards. A full write up explaining the operation of his circuit, along with the schematic is available.
Via the contact form.
Opossum over at 43oh has released a tiny version of the C printf() function for use in MSP430s where memory space is at a minimum.
Via 43oh.
Bertho entered his Lights out game into the Open 7400 Logic Competition.
After working out the math behind lights out, Bertho decided to make his own using only logic chips. The object of the game is to turn the lights off by using a + shaped mask.The board automatically generates random patterns over a 5×5 LED matrix, and by adding a solvability test into the design he insured that each random pattern is solvable.
He also added a replay option, so the user can have multiple reruns at completing the game. A manual pattern input is available for users who want to solve their own patterns. Check out the video of the game in action below.
Via the contact form.
R-B built a heart rate measurement from fingertip circuit. He also provided all the design files, and general theory of it’s operation:
This project describes a microcontroller based heart rate measuement system that uses optical sensors to measure the alteration in blood volume at fingertip with each heart beat. The sensor unit consists of an infrared light-emitting-diode (IR LED) and a photodiode, placed side by side as shown below. The IR diode transmits an infrared light into the fingertip (placed over the sensor unit), and the photodiode senses the portion of the light that is reflected back. The intensity of reflected light depends upon the blood volume inside the fingertip. So, each heart beat slightly alters the amount of reflected infrared light that can be detected by the photodiode. With a proper signal conditioning, this little change in the amplitude of the reflected light can be converted into a pulse. The pulses can be later counted by the microcontroller to determine the heart rate.
Reminder to all those interested in entering their projects into our Open 7400 Logic Competition: You only have two days left to send your entry in.
Entering
Entries can be posted on in our forum, on your personal blog, or even a handy how-to site like Instructables. When you’re ready, please submit a link to your project via the contact form.
Prizes
Foxit built himself a free Schazamp’s breakout board for the Bus Pirate.
Via the contact form.
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.
Drewmerc bough a 2in1 soldering station and decided to use the hot air gun to bend some plastic for a Bus Pirate case. After a trial and error learning exercise he succeeded in finishing his case.
Via the forum.
Get your own handy Bus Pirate for $30, including world-wide shipping. Also available from our friendly distributors.
MD Schmidt developed an online utility for viewing graphs stored by the DSO Nano. It was made to be used with BenF’s firmware mod that allows, amongst other things, DSO Nano to save it’s waveforms in xml format on a SD card. The online utility takes the xml file and displays the waveforms.
Open-source energy monitoring system is being developed.
This is a project to develop and build open-source energy monitoring, control and analysis tools for energy efficiency and distributed renewable microgeneration.
The design uses the Arduino to read pulse signals from the utility meter to get information about overall consumption. It also uses current transformers to read consumption details from independent lines, and temperature sensors to get temperature readings.
The information will be displayed on a wireless graphic LCD display, or accessed from a internet connection provided by the Ethernet or WiFi. The system will be accompanied by emoncms software which will provide data analysis for the user. Check out a demonstration of the system in the video below.
Seeed Studio is getting into the Halloween spirit, they are giving away blinking buttons to any purchaser from 8th to 17th of October. They are also rewarding first 50 Halloween themed pictures to be posted on their flickr account with a pirate head wrist strap.
There is also a Halloween contest:
This is a competition to see who can build the best and coolest Halloween-related stuff. Basically, you can build anything Halloween-related (e.g. costumes, pumpkins, monster masks whatever) that is enhanced with electronics in whatever way you think fit.
Via contact form.
In this video Jeri Ellsworth demonstrates her design of a Continuously Variable Slope Delta (CVSD) audio compression codec in an FPGA. She was in need of a replacement for a damaged HC-55564 IC from (where else) a pinall machine and reverse engineered the chip, coding up a replacement in a Xilinx FPGA on a Papilio One dev board.
Chris added another entry to the Open 7400 Logic competition: TTL Tilt Sensor.
His device works by converting accelerometer analog outputs into digital signals via 3×4 comparators, 6 are used for the X-axis and 6 for the Y-axis. From then on discrete logic chips are used to convert the different signals into various positions on a 8×8 dot matrix LED display. Since the dot matrix display only allows for one row of LEDs to be on at one time, he used a demultiplexer that cycles trough the rows in succession while maintaining persistence of vision for the user.
He made his schematic available, as well as lots of information and theory about its function. Check out the video of the device in action below.
Via the contact form. Continue reading “7400 competition entry: TTL Tilt Sensor”
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:
You can get IR Toy v2 for $22.05, including world wide shipping.
Rossum built an e-book reader for the microtouch. He wanted to use the common e-book format epub. But unfortunately since the format is actually a compressed set of text, html links and images, it was too much for the 8-bit microcontroller to handle.
To overcome this he developed a transcoding tool (epubgrider) to decompress the data, and format it so the device could handle it. Once the book is transcoded it is saved to a microSD card which the device reads and displays via the firmware he developed. Check out the video of it below.
Via HackaDay.
Fcobcn built a free PICqueño PCB. The device is functional with USB power only, as he left out the external power supply circuitry.
Follow some of our other PICqueno build videos.
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.
TitanMKD has finished up his USB host driver for Android open accessory on EvalBot. He added an external power supply for host applications that can now draw up to the 500mA specified by the USB standard. He also provided an example of it communicating with the DemoKit.
Adam submitted his Open 7400 Logic competition entry, a 16 button keypad that outputs the hexadecimal value in a 4 bit binary equivalent.
Adam wrote
This is a handy device for prototyping, etc… It’s a hexadecimal keypad (0..9, A..F) that outputs the hexadecimal value on 4 digital binary lines (one nibble). It has both active high and active low output (so it’ll work for any system), as well as active high and active low strobe outputs for when the data is on the lines. I also added an on/off switch for convenience.
Via the forum.
Maurício developed a Arduino based project for controlling devices in your home over the web. The site is in Portuguese but the video has English captions. The project uses the ethernet shield to allow you to interface with the Arduino over the web, which in return controls relays.
How to turn on lights, and various home appliances is demonstrated in the video, as well as how to get rid of useless garage door remotes. All of this is done via a smartphone with internet access. He has provided the source code for the firmware.
Carl Nobile has developed and released an Arduino library covering the HC-SR04 ultrasonic sensor. He writes: “It features timing, metric conversion, and standard deviation methods, plus a few support methods. It is written in C++ to conserve the namespace. The conversion formula can be easily modified to optimize the accuracy of conversion at different distances for inches and centimeters. Multiple buffers of different lengths can be created for determining standard deviation.
Look at the code and examples to understand how the library works. The standerd deviation code can be removed from the compilation resulting in a significant savings of resources. To do this comment the #define COMPILE_STD_DEV definition in the header file.”
You can download this library from cnobile’s Freshmeat webpage.
The backwoods logger mini from Big mess o’wires is a thermometer and altimeter for logging your cross country hikes. It is an updated version of the backwoods logger classic. A production test run of pre-assembled units is available for sale. All the PCB files, as well as the source code are available.
It measures temperature and air pressure, elevation is derived from the change of pressure. The sensor information, as well as graphs over time are displayed on a OLED display. It also has a screenshot function to save current data on the display for latter review. Using one AAA battery it can go up to 5 months before a recharge or replacement is needed.
