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Friday, September 26, 2014

Using Serial Port PC Battery Charger Circuit Diagram

This is one of the porters of the series "battery chargers that will never do." It uses the serial port of a PC to power a battery charger. A serial interface port can not supply enough current to charge batteries more powerful, but low capacity battery Nickel Cadmium (NiCd), this circuit is more than enough.You could, for example, use the batteries in a radio and charge them while using the PC.

The three serial port connections TxD, DTR and RTS, when not in use, are -10 V and can provide a current of about 10 to 20 mA. The circuit shown supplies a charging current of about 30 mA. If you need to change the polarity of the charging circuit, then it is a simple job, just reverse the diodes and use of software, change door signs to 10 V. Those interested can also write a software routine that automatically recharges the batteries.

Serial Port PC Battery Charger Circuit Diagram

Tuesday, November 26, 2013

Stereo PC Speaker Powered USB Speaker

This is the circuit diagram of USB powered computer speaker, or it widely known as multimedia speakers for PCs. The circuit has single-chipbased design, low-voltage electrical power supply, compatibility with USB power from computer, simple heat-sinking, inexpensive, large flexibility and wide temperature tolerance.

At the heart of the circuit is IC TDA2822M. This IC is, actually, monolithic type in 8-lead mini DIP (Dual Inline Package). It’s designed for use as a dual audio power amplifier in battery powered sound players. Features of TDA2822M are very low quiescent current, low crossover distortion, DC source voltage down to 1.8 volts and minimal output power of approximately 450 mW/channel with 4 ohm loudspeaker at 5V DC supply input.

An ideal power amplifier can be basically described as a circuit which can supply audio power into external loads without having producing substantial signal distortion and without having consuming extreme quiescent current.

This circuit is powered by 5V DC source obtainable from the USB port of the Computer. When electrical power switch S1 is turned to ‘on’ position, 5V power supply is extended towards the circuit and power indicator red LED1 illuminates immediately. Resistor R1 is actually a current surge limiter and capacitors C1 and C4 work as buffers.

How the circuit works..?

The operation of the circuit is very simple. Audio signals from the Computer audio port or headphone port are fed towards the amplifier circuit via R2 and C2 (for left channel), and R3 and C3 ( forright channel). Potensiometer VR1 used as the volume controller for left (L) channel, while potensiometer VR2 used to control the volume level of right (R) channel. Pin 7 of TDA2822M receives the left channel sound signals and pin 6 receives the right channel signals by way of VR1 and VR2, correspondingly. Amplified signals for driving the left and right loudspeakers can be obtained at pins 1 and pin 3 of IC1, correspondingly. Components R5 and C8, and R6 and C10 form the classic zobel network.

Construct the circuit on a medium size, general purpose PCB and enclose inside a appropriate case. It really is recommended to utilize a socket for IC TDA2822M. The external connections ought to be made working with suitably screened wires for improved result.

source: http://circuitdiagram.net/usb-powered-stereo-computer-speaker.html