This project is an Arduino based network status monitor. Eric Ayars wanted a unit to serve as an early-warning system for network problems so he concluded using LED as signs. When the leds light green the system is fine, when the leds light red Arduino is detecting a problem and when the leds light yellow-orange the Arduino is unable to detect the system status. The unit is able to monitor 13 systems and the software requires two separate programs: one to run on the host machine and determine the status of the various machines on the network, one to run on the Arduino and control the lights based on the information it gets from the host. Check details on the link below.
Arduino Network-status indicator - [Link]
Eric Ayars build this simple Christmas-tree water-level sensor to monitor the amount of water available for his Christmas tree. The design is based around a ATTiny85 microcontroller and uses easy to find electronic components, like a buzzer, a resistor, a led and some batteries. If you want to know how to program ATTiny45/85 using the Arduino, read this nice MIT tutorial. [via]
Christmas-tree water-level sensor - [Link]
Bill uses a replica of the point contact transistor built by Walter Brattain and John Bardeen at Bell Labs. On December 23, 1947 they used this device to amplify the output of a microphone and thus started the microelectronics revolution that changed the world. He describes in detail why a transistor works by highlighting the uniqueness of semiconductors in being able to transfer charge by positive and negative carriers.
How the world’s first transistor works - [Link]
In this project we design low cost high performance programmable home security system using few LDR’s as an input sensors. When above sensor(s) get triggered system may dial the user specified phone number (using build-in DTMF generator) and activate the high power audio alarm and lights. All the parameters of DTMF generator, audio alarm and light interface are programmed through the RS232 serial interface.
Current firmware of this system presents interactive control system through the RS232 interface. This control system consist with the menu driven configuration options, self tests, system report generators, etc.
This system also contain 5W (with 4Ω speaker) audio alarm with three selectable tone configurations, which include Police siren, Fire engine siren and Ambulance siren.
This system uses a Microchip’s PIC16F877A as a main controller, LM339 as sensor interface, UM3561 as a tone generator and μPC2002 as a speaker driver (audio amplifier). LM7805, LM7812 and LM317 voltage regulators are used to obtain +5V, +12V and +3V respectively.
All the project source codes, schematic diagrams and PCB patterns are available in “http://elect.wikispaces.com/Programmable+Home+Security+Alarm+System” with terms and conditions of GNU GPL and Creative Commons – Attribution-ShareAlike 3.0 Unported license
Programmable Home Security Alarm System – [Link]
EL Wire, also known as Electroluminescent wire, is a stiff wire core coated with phosphor and then covered with a protective PVC sheath. When an AC signal is applied to it, it glows an aqua (blue green) color. Sometimes its covered with a colored plastic shell to make it appear another color. It looks a little like thin neon. Very bendable, it keeps its shape and you can curl it around your finger.
Electroluminescent wire tutorial – [Link]
This project is a PCB etching solution rocker that uses a servo motor to agitate the etching solution. The base is build from wood and the servo is controlled by a PIC 18F2620.
PCB Etching Solution Rocker – [Link]
This project is a wireless temperature and humidity sensor based on Sensirion SHT15 sensor and PIC18F1220. The unit is wirelessly sends the readings to a base station to display and log the data. The wireless link is implemented using XBee RF modules.
Wireless Temperature and Humidity Sensor – [Link]
This project is a solar irradiance meter based on TSL230R Light-to-Frequency converter and Amicus 18F25K20.
This chip features an “electronic iris” to facilitate measurements over a wide range of intensities. The photo sensor may be enabled in 3 stages to measure from near darkness (the glow of a computer monitor) to full-intensity sunlight. The output of the sensor is a pulse stream whose frequency is proportional to irradiance.
Solar Irradiance Meter - [Link]
Graham explores a popular method for charging NiMH cells – float charging.
Float charging has the advantage of keeping the cells fully charged and ready to use without the potential damage of long-term trickle charging or the cost of low-discharge cells. This approach works because NiMH cells do not have the memory problems associated with Nicads.
Float Charging NiMH Cells - [Link]
This project is a meter clock that is styled like a VU meter. The two meters are attached to servo motors and are controlled by a PIC 18F2550. The box is build by y first making a form, then laminating thin sheets of wood. Complete project documentation can be found on the link below. [via]
Meter clock in wooden box – [Link]