Wiring Material: 1

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Friday, October 17, 2014

1 W Home Stereo Amplifier Rise

This is a one watt home stereo amplifier module project using the KA2209 IC from Samsung, which is equivalent to the TDA2822. It operates from 3-12V DC & will work from a battery since the dormant current drain is low. It requires no heat sink for normal use. The input & output are both ground referenced. Maximum output will be obtained with a 12V power supply & 8 ohm speaker, however it is suitable for driving headphones from a supply as low as 3V.

The Specifications of the home stereo amplifier :

D.C. input : 3 – 12 V at 200 – 500 mA max
Idle current : approx. 10 mA
Power output : > 1 Watt max. 4-8 ohms, 12V DC
Freq. Resp. : approx. 40 Hz to 200 kHz, 8 ohm, G=10
THD : < 1 % @ 750 mW, 4-8 ohm, 12V
Gain : approx. x10 (20 dB) OR x100 (40dB)
S/N ratio : > 80 dB, G = 20 dB
Sensitivity : < 300 mV, G = 20 dB
Input Impedance : approx. 10 k ohm

Description

The gain is adjustable from ten to 100, i.e. twenty to 40 dB. Start with feedback resistors R1 and R3 of 1k ohm, this will give a gain of ten which ought to be adequate for most applications. In case you need more gain, you can remove resistors R1 and R3.This will give a gain of about 100, or 40 dB.The input attenuation can be adjusted by the potentiometer which can be used as a volume control. The IC gain ought to be kept as low as necessary to accomplish full output, with the in put potentiometer and your signal source at maximum.

1 W Home Stereo Amplifier Circuit Diagram

Voltage Gain = 1+ R1/R2 = 1+R3/R4, however the maximum gain with no outside feedback is about 100, or 40dB. (GdB = 20log Gv)

This will keep the signal to noise ratio as high as feasible. Additional gain provided by the amplifier will reduce the S/N ratio by a similar amount, since the input noise figure is constant. Other values for R1 and R3 of between 1k and 10k ohm can be used if an intermediate gain level is necessary.

If driving a pair of headphones, you may also need a 100 ohm resistor in series with each output to reduce the output level, depending on headphone impedance & sensitivity. Make positive you start with the volume right down to check. Numerous headphones may be driven from the amplifier in the event you wish, since most headphones have at least 16 ohm impedance, or more often 32 ohm.

There are only a few outside parts, the IC contains most of the necessary circuitry. R1,R2 and R3,R4 are the feedback resistors. C1 provides power supply decoupling. C2 and C3 are the input coupling capacitors, which block any DC that might-be present on the inputs. C4,C5 block DC in the feed back circuit from the inverting inputs, and C6,C7 are the output coupling capacitors. C8, R5 and C9,R6 act as Nobel networks providing a high frequency load to maintain stability at frequencies where loud speaker inductive reactant may become excessive. The pot provides adjustable input level attenuation.

Sunday, October 12, 2014

Power Supply 5V 1 3 3A by LM2575

POWER1 is a switched power supply specially designed for use with modern single board computers. The mechanical dimensions match exactly those of the SBC ZWERG11A. Due to the small mechanical dimensions and the modern design, POWER1 can be used in all applications requiring a regulated voltage of 5 Volts DC, up to 3 Amperes. Voltage regulation is done with a component from National Semiconductor, known as “simple switcher”. Regarding the amount of extra components one can really call the design “simple”, yet resulting in a reliable and low-cost power supply.

Saturday, October 4, 2014

1 5 Volt Tracking Transmitter

The current draw for this tracker is 3.7mA, so the 1.5V button cell will last awhile. What the heck am I suppose to hear you ask? When your circuit is working you should see the LED flash quite fast. Take your FM radio and search for the low-beat humbe-humbe-humbe-etc equal to the flash of the LED (probably around the 100Mhz). Found it? If that position is interferering with a radio station you can fine-tune it with the variable capacitor.

If you like to have the tracker around the 88Mhz you can do that by spreading the windings from the home-made coil just a bit (1/2 a millimeter or so). Anyways, play with it and learn. It is a nice project. The 12-inch antenna can be anything, it is not really that critical. I used a piece of 22 gauge flexible wire. I havent checked the range but will do that shortly.

* For stability, use a NPO types for C2 & C4.
* Resistance tolerance for R1 should be 1 or 2%.
* Frequency range is the usual 87-109Mhz on the FM dial.
* The coil is made from 22 ga hookup wire, like the solid Bell phone wire. Leave the insulation on.
* The LED is the High Brightness type for maximum illumination.

Partlist
C1= 100uF electrolytic capacitor
C2= .01uF disc capacitor
C3= 4 to 40 pF trimmer capacitor
C4= 4.7 pF trimmer capacitor
L1= 0.1 uH, 6 to 8 turns of 22 gauge hookup wire close wound around a 1/4" diameter non-conductive core, such as pencil
IC1= LM3909 LED flasher
LED1= Red LED
Q1= 2N3904 NPN silicon transistor
R1= 10K
Antenna= 10 to 12 inches of hookup wire