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25 Jan 2008


PC can display CPU fan speed via simple application. Another option is to go to BIOS menu and read fan speed value. But if you want to have stand alone device that measures CPU cooler fan speed so here it is. It is a PIC16F627 based fan tester with four 7 segment LED displays.

CPU fan sends tachometric pulses via separate wire and can be calculated as RPM. PIC captures and calculates the time by using two timers/counters. One captures pulses and another calculates elapsed time. For instance, by capturing the amount of pulses within the period of 1 second would yield the frequency at which the fan spins, e.g. 60Hz. To convert to RPM it is a simple matter of multiplying the frequency in Hz by 60, which in this case yields to 3600 RPM. Schematic is simple – the most components are used for interfacing LED displays. They are controlled via BCD converter and transistor keys. Fan pulse wire connects directly to PIC pin via pull-up resistor as amplitude of fan pulses is same as PIC power supply – 5V.

Stand alone CPU cooler fan speed tester – [Link]

25 Jan 2008


RFID cards are commonly used in many areas like access control, security, and for other identification purposes. One of simplest cards to read are HID ISOProx that don’t use any encryption. Their carrier frequency is 125 kHz.

Hardest part in this reader project is the reader itself as it has to power the tag with magnetic field and sense the transmitted signal. For this series resonance of 150 kHz circuit – antenna is used. Signal from antenna is passed through low pass and band pass circuits and then to PIC comparator, where RFID FSK pulses are detected and decoded. Latest ASM source can be seen here. Probably RFID reader could use more advanced microcontroller than PIC16F628A for more efficient signal reading by using interrupt based compare capture module as this one already uses it for 150 kHz carrier signal generation. [via]

RFID reader based on PIC microcontroller – [Link]

25 Jan 2008


If you are a rocket modeling hobbyist and need simple and reliable rocket timer with adjustable time this project is for you. Timer can be set from 1s to 15s by using 4 dip switch IC. Depending on switch binary position 2^4=16, the time is set when second stage of rocket has to be ignited.

Project is based on common PIC16F84 running at 4MHz. MICROCHIP TC4422 is used to control the voltage and current to the “igniter”. Timer also has two failsafes to avoid accidental ignition. Device is powered from 9V battery and is small size as weight is critical in rocketing. Program is written in assembly language. [via]

Simple 1s to 15s rocket timer – [Link]

25 Jan 2008


George has a great page of DC motor tips, he writes –

A small DC motor generates torque by creating an interaction between a fixed and rotating magnet field. The fixed field is supplied by high energy permanent magnets. The rotating field is created by passing a DC current through several different windings on the armature (rotating part) and timing which winding is powered through a device called a commutator. Power is applied to the armature by brushes which ride on the commutator.

To understand how a motor responds to load, the motor itself is modeled by dividing it up into three major components. These components are the ideal motor, a back-EMF generator and parasitic resistance. These parts are really not physically separable, but for modeling purposes this is convenient.

Small DC motor tips – [Link]

25 Jan 2008


Here’s a massive page on Molex connections and how to do terminal pin crimping, worth a read and a bookmark.

Molex connectors and terminal pin crimping explained – [Link]

25 Jan 2008


Mikes writes in –

Since Make is all about great hardware projects, I figured I’d let you know about a project that aims to develop a fully VGA compliant video card in true open source fashion. Kerneltrap now has an interview online about the motivations behind the project, when the card will be available and what it’s performance will be. With the first prototype already working after just a few months of development, it’s a matter of time before developers can get their hands on one of these. [via]

Low cost open source VGA compatible video card – [Link]

25 Jan 2008


Mathieu writes –

I whipped up a little interface yesterday, to connect an Arduino to a Radio Control Transmitter. This can be used to send commands from the Arduino to the transmitter, which will mix them with the manual input and radio them to the radio-controlled model.

The Arduino is sending commands (PPM-encoded series of servo-position pulses) to the RC transmitter (a Multiplex Royal Evo 12, in this case), which mixes them with manual input and radios them to the radio-controlled model.

You can see on the transmitter’s display that channels 1, 2, 4 and 5 are broadcasting values while the sticks are centered. If I had video, you could see them change over time under the Arduino’s control.

Arduino to radio-control transmitter interface – [Link]

25 Jan 2008


The folks from Libelium sent in their Arduino contest, looks interesting –

It is a contest for everyone who believes in Open Hardware and enjoys hacking with Arduino. It is the time to show what you have done and share it with the Community! There are 3 different categories:

  • Common life hacks. Have you designed a remote-pets-feeder? A gadget for watering your plants? A GPS navigator for your bike? Or anything that makes your life easier?
  • Art hacks. Artistical installations, interactive objects… just show the limits of your imagination.
  • Robotics.

The winner of each category will get one GPRS/GPS Module for Arduino. One of the exclusive and limited edition for Arduino whe are going to release. It will let Arduino to connect to the mobile networks, make and receive phone calls, send and receive sms’s!, give the GPS coordenates… A new level of modules for Arduino. [via]
Arduino contest – [Link]

25 Jan 2008


Dubbed the “Flying Stick Camera,” it uses kinetic energy built up by rubbing the stick together between one’s hands like it’s smaller toy variant. The difference is that the Flying Stick Camera stores that energy and actually flies up into the air like a helicopter. When the energy is dissipated, it auto-rotates back down to the ground. Meanwhile, while it’s soaring high above one’s head, the Flying Stick will snap off an array of digital shots at a preset interval. And with face detection built into the digital design, the subject is always in focus.

Flying Stick Cam – [Link]

24 Jan 2008


Anykits manufactures and supplies a large variety of Do It Yourself (DIY) electronic kits and modules for various applications. They also offer components, prototyping supplies and other related product accessories. The cool think is that they provide a PDF “magazine” with open source designs. Be sure to check it out!

Anykits electronic kits + Open Source Circuits – [Link]





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