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26 Sep 2010

Last week I had a big flood in my house. A water tube broke in the middle of the night making lots of damage. Wooden floor, furniture, small electronic appliances, all damaged due to the water. This made me think on a project that would sense water on the floor and trigger an alarm.

The detector should be able to sense water and trigger an alarm. Also it should be small and battery operated. Battery’s voltage should be checked also.

Flood Detector – [Link]

26 Sep 2010

This tutorial shows how to use the Timer1 module inside PIC12F683 as an asynchronous counter to compute the frequency of an external clock source. The external clock is connected to the GP5/T1CKI port of PIC12F683 and the measured frequency value is sent to a PC through serial port to display on an hyperterminal window. A 555 Timer IC operating as an astable multivibrator is used as the external clock source. The Timer1 module is 16-bit so it can count up to 65535. If the Timer1 is turned ON for 1 sec, the maximum frequency it can measure is 65535 Hz. Any frequency higher than this will create Timer1 overflow. An interrupt service routine is also written to demonstrate how to detect the overflow and take appropriate action. This concept can be extended to measure higher range frequencies.

How to measure frequency of an external clock source using PIC – [Link]

25 Sep 2010

This is a 9V power supply which will work even on power failure. It uses a rechargeable battery and regulators. A transformer with 15-0-15 AC volts output is required.

Battery Backup Supply – [Link]

25 Sep 2010

The 555 Astable generates a clock for this circuit, an oscillator giving a square wave output at pin 3 which is counted by 4017 to give a running lights effect.

The decade counter-divider CD4017 has 10 outputs, for every low to high transition at the clock input, rising edge, the counter advances one LED. After going one full circle the the first LED lights again and it goes on. You can vary the value of R2 100K Linear potentiometer to make LEDs run fast or slow.

Running Lights with CD4017 – [Link]

25 Sep 2010

FreePCB is a free, open-source PCB editor for Microsoft Windows, released under the GNU General Public License. It was designed to be easy to learn and easy to use, yet capable of professional-quality work. It does not have a built-in autorouter, but it can use the FreeRoute web-based autorouter at www.freerouting.net. Some of its features are:

  • 1 to 16 copper layers
  • Board size up to 60 inches by 60 inches
  • Uses English or metric units (i.e. mils or mm) for most functions.
  • Footprint libraries courtesy of Ivex Design International, PCB Matrix and the IPC.
    Copper fill areas
  • Footprint Wizard and Footprint Editor for creating or modifying footprints
  • Imports and exports PADS-PCB netlists
  • Exports extended Gerber files (RS274X) and Excellon drill files
    Design rule checker
  • Autosave

FreePCB open-source PCB editor – [Link]

25 Sep 2010

TinyCAD is a program for drawing circuit diagrams commonly known as schematic drawings. It supports standard and custom symbol libraries. It supports PCB layout programs with several netlist formats and can also produce SPICE simulation netlists.

TinyCAD for schematic drawings – [Link]

25 Sep 2010

The Ether Card is a basic Ethernet interface for use with the Carrier Board. The ENC28J60 chip is used to drive the on-board RJ-45 connector, including two status LEDs. It can connected to the JeeNode (and many other similar boards, such as Arduino and RBBB) via the SPI bus.

EtherCard – cheap Ethernet module with ENC28J60 – [Link]

25 Sep 2010

This project is a servo tester based on PIC16F690 and with code written in C. The timing loop is a crude one relying on a simple tight loop, so the pulses are not massively accurate.The board has four modes of operation, selected using TACT switches with the status indicated on LEDS built into the switches .

Servo Tester Module – [Link]

25 Sep 2010

This project is a slide-show forward/backward button in the size of a USB-key.

Those old slide-projector had normally a handy button with a cable where you could advance to the next slide or go one back. I was looking for something like that. I have tried to use a USB wheel mouse but it is not the same. You click accidentally on the wrong button and you get a context menu or you scroll too many slides at once.

A USB slide show presenter – [Link]

25 Sep 2010

This project is a 555 timer based PWM controller features almost 0..100% pulse width regulation while keeping the oscillator frequency relatively stable. The frequency range from about 170 to 200 Hz. Check schematic on the link below.

Simple PWM controller – [Link]





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