Tuesday, March 25, 2014

CCFL Tester Circuit For LCD Screens

Lcd's cover a wide range of applications including led tv's to cmputer monitors, PDAs, digital monitors and much more. LCD backlight mainly consists of a light source, diaphragm, light leading board and a plastic frame.  Cold-cathode fluorescent lamps (CCFLs) have a phosphor coated glass cylinder with cathodes at each end. The CCFL inverter accepts a low-level DC input voltage and provides a high-level AC output to run the backlight CCFL tube. Here's a CCFL tester circuit that often needed to check a faulty LCD backlight circuit for finding the dead components.

Guitar Preamplifier Circuit Using IC TL071

Here is the circuit of a electric guitar preamplifier based on IC TL071.The pickup device has a transducer on one end and a jack on the other end. The jack can be plugged into a preamplifier circuit and then to a power amplifier system.

The mechanical vibrations from low frequency bass to a certain extent of high frequency is picked up by a guitar or violin pickup device and converts them into an electrical signal, which can then be amplified by an audio amplifier. This circuit diagram of guitar pre amplifier has two output options - one to a power amplifier and other one could fed to a headphone.

Friday, March 14, 2014

150mW Crystal AM Transmitter

Here is the circuit of a medium power crystal based amplitude modulation (AM) transmitter that can deliver 100-150mW of radio frequency (RF) power.

Tuesday, February 25, 2014

1Hz Clock Generator Circuit Using COB

Let's familiarize with a COB - chip on board device by building a precision 1Hz clock generator. Circuits that usually generate 1Hz clock makes use of ICs with variable capacitors but they are not very precise. ( micro controller based one should be precise but it costs large ). better accuracy can be obtained by a COB found inside a digital clock, which is cheaply available in the market.

Sunday, February 23, 2014

Simple Laptop Audio Amplifier Circuit

When it comes to laptop sounding, most of the laptops currently in the market has very low sound output (laptops like DELL XPS is an exception). If you need more powerful sound, you need to amplify the sound output from the laptop. Here's a simple amplifier circuit making use of the SANYO LA4440 IC which is ideal for low power audio applications because it gives better sound clarity and less distortion.

Laptop audio amplifier circuit

Fortunately the circuit diagram is very simple and even a beginner can assemble and debug it. The circuit is built around the previously mentioned LA444o IC and a few components. The amplifier is a dual channel one with 6W for each channel. So a 10 W speaker would be very sufficient. Connect pins 2, 6 and ground of IC1 to the stereo jack which is to be used with the laptop.

LED Running Display Using NE555

Here's a circuit to build a led based running display using easily available general purpose timer IC NE555 and a popular decade counter IC CD4017. This display consist of 24 LED's of four layers. The NE555 is wired as an astable multivibrator whose output triggers CD4017 counter.

Wednesday, January 29, 2014

Simple Adjustable DC - DC Converter

It's easier to generate DC from AC mains supply using a transforme and some diodes but the difficult part comes when we need to regulate the supply to feed sensitive devices such as mobile phones. Here's a versatile DC to DC coupler that 'll give you regulated fixed dc output voltages like 5V to charge mobile phone, 12V for external hard drives etc. You may use a 19V laptop adapter to route various voltages such as 5V , 6V, 12V from it.
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