Inductance Capacitance Meter

We all know that the most troublesome components in electronics are inductors and capacitors. Usual ones have high tolerance, time has an effect on them and their cost can be quite big. Besides that, i believe there are other people like me, who have boxes full of salvaged components from things that couldn’t be repaired. Now, from those components, you can measure capacitors and inductors with the tool presented in this project.

The L/C meter presented has a pretty good accuracy, +/- 1% of reading +/- 0.1pF or +/- 10nH. The measurement method is not the usual one but it’s very interesting, first the microcontroller measures the frequency of the oscillator, then measures the frequency of the oscillator with an added known capacitor and last time it measures the frequency of oscillation with the unknown component added.

In my opinion this method is a good approach if you can measure the frequency accurately. If we look at the equations described in the project that gives us the value of the unknown component we observe it only depends on those three frequencies and the value of the added capacitor. So we have only one element in our equation that isn’t measured, Ccal which can be chosen to be a higher quality capacitor with low tolerance and thus each time you calibrate the meter the frequencies are measured again and the calculations will be more accurate in case some component from the oscillator changed its value a bit because of temperature for example.

Another good function it that it can show you the difference between two components, very useful for matching. The oscillator is done using a LM311 comparator with the resonant circuit in the positive feedback loop. The microcontroller used is a PIC16F84, the assembler code is available as well as the hex files and schematic.

Inductance/Capacitance Digital Meter: [Link]

April 21st, 2008

Blu-Ray Laser Pointer

 Blu-Ray Laser Pointer on a piece of paper

We all know the Sony Blu-Ray replacement drive assembly for the PS3 and the Blu-Ray Laser phaser project i mentioned in a past article. So we know its possible to build a Blu-Ray Laser with one of these modules, but what makes this project better than others ? It seems the author payed a little more attention to details and added a current-limited power supply opposed to the simple resistor based design. The project also features rechargeable Li-Ion batteries with charging jack on the back and a protection circuit module for Li-Ion batteries. So you can see now that this project brought many improvements to the original one.

Blu-Ray Laser Pointer: [Link]

Ethernet based Security System sends you an Email when the alarm goes off

The need for security systems is growing every day. These days every institution has an alarm system, and people houses are beginning to catch up. One of the features included in most security systems is the sms notification, which the author thinks is not as reliable as Ethernet Notification system because GSM networks can have a congestion at the time the alarm.

Well i disagree with the author, and i think the SMS notification is much more reliable than Ethernet, in fact from my experience Ethernet Networks tend to fail more often that GSM networks. So if you’re thinking of building a security system, i would suggest a SMS notification system instead of an ethernet one, in my opinion sms is more reliable.

Ethernet based Security System sends you an Email when the alarm goes off: [Link]

MAX6953 LED Matrix or development board

The MAX6953 from Dallas Maxim is a compact cathode-row display driver that interfaces a microprocessor (like PIC or AVR) to four 57 dot matrix LED display trough an I2C compatible serial interface. The Max chip includes some nice features like:

  • low-power shutdown mode
  • segment blinking
  • test mode that forces all LEDs on
  • 16-Step digital brightness control

This project can be considered both a led matrix controller and a development board for MAX6953. The project presents only the max6953 and the led matrix, if you want it to display anything, you’ll also need to stick a microcontroller in there and write some code. You might want to check this other article 507 LED Matrix which has everything included.

MAX6953 LED Matrix or development board: [Link]

April 21st, 2008

Blinking LED at 230V

 Blinking LED at 230V

Before working with project like this, that use high voltage, take serious precautions, because 230V is lethal. Now lets get to the circuit, which is not much of a circuit, just 2 resistors, 1 capacitor, 1 diac and the LED. The capacitor charges by the diode and the resistor. When the voltage on the capacitor achieves 30V the diac “releases” the electrical tension and the capacitor empties thorough the diac, LED blinks. The blinking time depends on the capacitor. There are various applications for this circuit, most in signaling something, but its not always necessary to use 230V so i would suggest not using this circuit unless its necessary.

Blinking LED at 230V: [Link]

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