Forum Diagram

Monday, November 3, 2014

HARTLEY OSCILLATOR

The Hartley Oscillator is characterised by an LC circuit in its collector. The base of the transistor is held steady and a small amount of signal is taken from a tapping on the inductor and fed to the emitter to keep the transistor in oscillation. The transformer can be any speaker transformer with centre-tapped primary. The frequency is adjusted by changing the 470p.

SAFELY DISCHARGE X CAPACITORS ELECTRONIC DIAGRAM

When the AC voltage is disconnected, CAPZero automatically and safely discharges the X capacitor by closing the circuit through the bleed resistors and directing the energy away from the exposed AC plug. This approach provides engineers with total flexibility in their choice of the X capacitor used to optimize differential- mode EMI filtering without worrying about the effect of the required bleed resistors on system no-load and standby power budget. The innovative design inherently meets international safety standards for all open and short-circuit fault tests, allowing CAPZero to be used before or after the system input fuse. CAPZero is suitable for all AC-DC converters with X capacitors that require very low standby power. It’s offered with 825- or 1,000-V MOSFETs to support a variety of power supply design needs. It is ideal for a wide range of applications, including PCs, servers/workstations, monitors and TVs, printers and notebooks, and appliances requiring EuP Lot 6 compliance and adapters requiring ultra-low no-load consumption. CAPZero devices are available now in an SO-8 package at $0.40 each for 10,000- piece quantities. [www.powerint.com]

Sunday, November 2, 2014

BURGLAR ALARM USING IC TIMER 555 556 ELECTRONIC DIAGRAM

BURGLAR ALARM USING IC TIMER 555/556 ELECTRONIC DIAGRAM

circuit diagram of burglar alarm using IC timer 555/556 is functioned as an alarm to prevent thief entering your house. The alarm would produce loud sound when a thin wire connecting resistor R1 with IC pin no 4 is broken. Thin fiber is used as the wire. The thinner the wire, the more responsive the alarm. This circuit needs 5-15V power supply, buzzer is used as a speaker. Here is the circuit schematic :

Parts list :

Resistor R1 : 10k
Resistor R2 : 68k
Resistor R3 : 1k
Polar capacitor C1 : 1uF/15 B
Capacitor C2-C3 : 0.01uF
IC Timer : NE555

AUDIO LEVEL METER ELECTRONIC DIAGRAM

It consists of only few components. IC LM3915 converts the audio analog voltage and display it to the LED. Here is the schematic :

Parts list :

Resistor R1 : 1k2
Resistor variable R2 : 10k
IC : LM3915
LED indicator LED1-LED10 : LED 5mm
12V power supply

4x25W CAR AMPLIFIER TDA7381 ELECTRONIC DIAGRAM

The extremely reduced components count allows very compact sets. The on-board clipping detector simplifies gain compression operations. The fault diagnostics makes it possible to detect mistakes during Car- Radio assembly and wiring in the car.

Absolute maximum ratings of IC TDA7295 IC

Operating supply voltage = 18 V
DC supply voltage = 28 V
Peak supply voltage (t = 50 ms) = 50 V
Output peak current Repetitive (duty cycle 10 % at f = 10 Hz) = 3 A
Output peak current Non repetitive (t = 100 µs) = 4A
Power dissipation, (Tcase = 70 °C) = 80 W
Junction temperature = 150 °C
Storage temperature = -40 to 150 °C

6 MILLION GAIN

6 MILLION GAIN

This circuit is so sensitive it will detect "mains hum." Simply move it across any wall and it will detect where the mains cable is located. It has a gain of about 200 x 200 x 200 = 6,000,000 and will also detect static electricity and the presence of your hand without any direct contact. You will be amazed what it detects! There is static electricity EVERYWHERE! The input of this circuit is classified as very high impedance.

source : http://www.talkingelectronics.com.au/projects/200TrCcts/200TrCcts.html

Saturday, November 1, 2014

400W Stereo Marshall Leach Amplifier

400W Stereo Audio Amplifier based on the original Marshall Leach involvement, but has made some improvements. Regarding the power supply voltage to the +-75V. VC comparing the performance of the modified Leach 700W/2R on one common board of both channels, as well as protection and control circuits for the fans. Compared to the 700W version a bit different in wiring. Because some things in the 700W version is completely tightened to perfection.

                                               700W version could criticize a couple of things:

1st very high gain output stage resulting in deterioration of signal noise distance. Therefore 700W version even more noisy.

2nd The absence of multipliers Ube bias current control and maintain temperature stability diagram. The 700W version of the thermal stabilization solved by a single transistor, which can sometimes cause a great loss due to power control is fast enough and has some delays. Therefore JPA400 added to this multiplier.

3rd Protection Error on board speakers, the amplifier is less comfortable and it is necessary to add this protection to the side somewhere special plate.

4th no possibility to correct the offset voltage of the amplifier output, this has a rather large weight in the differential pair of transistors and voltage level. Here this is solved by means of trimmer connected to the input Mark

5th The work points the individual stages are laid pretty low, it will also cause an increase in total harmonic distortion as well as intermodulačního distortion.

All this is in JAP400 removed. The input amplifier is Mark with adjustable offset voltage. Mark is mainly due Preamplified signal for generating the actual end-impedance amplifiers and separates. The differential amplifier is a classic symmetrical with the current 5 mA per couple, which is about 2.5 mA each transistor. Equally, shifted the operating point voltage amplifier to approximately 13 mA. This modified driver will provide enough power for generating terminal transistor and is hard enough. At the end of this time is five pairs of end-type transistor 2SC5200 / 2SA1943. Current policy is converted into the number of transistors. It has a negative slope and replicates the characteristics of SOAR terminal transistors. Current protection for amplitude limitation limits the end-around transistors 7A. As has been mentioned on the thermal stabilization of the multiplier is used Ube, is formed by two NPN and PNP transistors.

The board also includes an amplifier circuit for the fan control. This circuit ensures that the fan speed control depending on temperature. At the temperature to 65 ° C, fan runs for about 30%, it greatly reduces noise. After exceeding this temperature, the fans start running at 100% and lights to signal overtemperature. fans again at reduced power switch at about 42 ° C. Thermal protection is associated with protection of the speakers at cooler temperatures exceeding 80 ° C, the speaker is disconnected. On board is a relay switch that allows stereo / bridge mode, the indikovám LED on the front panel. The amplifier also includes an auxiliary power source to the main board, formed by transistor stabilizer. Due to higher electric circuit protection circuit and fan control. There is also an indicator of an excited, solved by the presence of the indicator signal and clip detector.

Technical parameters:

Output power:                      2x 400W/4R, 2x230W/8R
Minimum holiday zázěž:     4R
Slew rate: 45V/us
Bandwidth:                           8-150 000 Hz /-3dB
Maximum permissible voltage: +-75V
Filter Capacity:                    2 x 20G / 80V
Sensitivity DC protection:    + /-2V
Late connection:    2 seconds
Fusing end amplifier:            4 8 A / F
Input sensitivity for maximum excitation: 1V