Diagram Plus guide

The designer of this circuit had fitted two (waterproof) loudspeakers in his bathroom and connected them to the stereo system in the living room via a long cable. Naturally, this promptly led to the desire to be able to use the remote control unit from the bathroom. Commercially available extension sets for this purpose were judged to be unsatisfactory, primarily because they require an additional IR transmitter diode to be fitted in front of the amplifier. Although the repeater shown here requires a length of coaxial cable, it provides a simpler, and above all more reliable, solution to the problem. The signal transmitted by the remote control unit is received by IR receiver IC2, and the (nearly) open-collector output of T1 is connected to the RC5 bus of the stereo system.

This proved to work excellently with Philips equipment, and it will probably also work with equipment from other manufacturers with a few small modifications. Voltage regulator IC1 is used here to allow the supply voltage to range from 8V to 30V, and diode D1 provides protection against a reverse-polarity supply voltage connection. A nice side benefit arose from the fact that the loudspeakers in question (Conrad models) have transparent cones and protection grilles with rather large openings. This made it possible to fit the tiny circuit, which was built on a piece of prototyping board, to the frame of one of the speakers, behind the cone. The whole arrangement is thus hidden, but the remote control still works perfectly if it is aimed towards the speakers.

The AN7147 Dual 5.3-watt Audio Power Amplifier from Panasonic is listed as a ‘replacement type’ so hopefully will be around for some time to come. Together with some extra components, it can represent a simple surround-sound system requiring no opamps or a negative voltage supply. As shown by the circuit diagram the basic stereo amplifier is changed into a surround-sound system by a trick called ‘adding feedback from the opposite channel’. When surround sound is required, the negative feedback signals supplied by C13-R3 and C12-R4 are fed to the inputs of the ‘other’ amplifier. The resulting phase difference causes the surround effect. If surround sound is not required, the effect can be disabled by pressing push-button S1.

Circuit diagram :

5.3W Amplifier With Surround System Circuit Diagram

This causes the bistable built around IC2.A and IC2.B to toggle and drive transistors T1 and T2 such that the above mentioned negative feedback signals are effectively shunted to ground. A high-efficiency LED and a 3.3-kΩ series resistor (R14) should be used to make sure the maximum output current of the CMOS 4001 device is not exceeded. The amplifier should not be loaded with impedances smaller than 3Ω. The AN7147 will typically supply up to 4.3 watts into 4 Ω. The SIL-12 case needs to be cooled wit a small heatsink of about 6 K/W or better. The quiescent current is modest at just 19 mA.

Source : www.extremecircuits.net

Most dimmers use pulse width modulation (PWM) to control the amount of power that is delivered to the lamp. Those that come bundled with a switch faceplate control the firing angle of a Triac on the 240V mains side. These work fine with resistive loads but may not be suitable for inductive loads such as low-voltage halogen lamp transformers. This circuit also employs PWM but it switches at a high frequency (22kHz) on the low-voltage side of the lamp transformer. This high frequency also simplifies EMI filtering. Furthermore, because this circuit is isolated from the mains by the transformer, it is relatively safe to build and install.

IC1 is a standard 555 astable oscillator with a high duty cycle. It produces a narrow negative-going pulse at its pin 3 output approximately every 45µs (ie, the frequency of oscillation is about 22kHz). These pulses trigger IC2, another 555 timer, this time wired as a variable monostable. IC2s pin 3 output is normally low which means that its internal discharge transistor is on and the 1nF capacitor on pins 6 & 7 is discharged. However, when the monostable is triggered (by IC1), its output goes high, the internal discharge transistor turns off and the 1nF capacitor charges via VR1 & VR2 until it reaches 2/3Vcc.

At this point, the output at pin 3 switches low again. Each time pin 3 of IC2 goes high, it turns on power Mosfet transistor Q1 which in turn switches on the lamp. Potentiometer VR2 is used to control the time it takes the 1nF capacitor to charge to the threshold voltage and thus sets the width of the output pulses. At maximum resistance, the pulse width is 55ms. This is longer that the 45ms period of oscillator IC1, and so IC2s pin 3 output is high for 100% of the time and the lamp operates with maximum brightness. Now consider what happens if the monostables period is shorter than the astables.


In this case, each time IC1s pin 3 output goes low, pin 7 of IC1 also goes low and discharges IC2s 1nF timing capacitor via D3. This retriggers the monostable. As a result, IC2 is triggered at a 22kHz rate and produces variable width pulses depending on the setting of VR2. Its output in turn pulses Q1 to control the lamp brightness. D2 isolates IC1s timing circuitry from IC2s. VR1 is used to set the minimum lamp brightness when VR2 is at minimum resistance. If this control is not required, VR1 can be replaced with a 1.8kO resistor. The 220µF capacitor on pin 5 of IC2 provides a soft-start facility to prolong lamp life.

Initially, when power is first applied, the 220µF capacitor is discharged and this lowers the threshold voltage (which is normally 2/3Vcc). That in turn results in shorter pulses at the output. As the 220µF capacitor charges, the threshold voltage gradually increases until the circuit operates "normally". For the prototype, Q1 was a BUK553-60A, rated at 60V, 20A & 75W. Q1s maximum on-state resistance is 0.1O, so switching a 4A lamp load results in a maximum power dissipation of 1.6W. The bridge rectifier comes in at around 5W and so both should be mounted on suitable heatsinks.

The power dissipation in the bridge rectifier can be reduced by using power Schottky diodes rated at 5A or more. The output of 555 timer IC2 is capable of directly driving several Mosfets (up to four in tests). Note, that if the Mosfet is going to be some distance from the 555, it will be necessary to buffer it. Power for the control circuitry is derived from 3-terminal regulator REG1 which produces an 8V rail. This in turn is fed from the output of the bridge rectifier via diode D1.

30 minutes operation, Blinking LED signals 6 last minutes before turn-off

The purpose of this circuit is to power a lamp or other appliance for a given time (30 minutes in this case), and then to turn it off. It is useful when reading at bed by night, turning off the bedside lamp automatically in case the reader falls asleep... After turn-on by P1 pushbutton, the LED illuminates for around 25 minutes, but then it starts to blink for two minutes, stops blinking for two minutes and blinks for another two just before switching the lamp off, thus signaling that the on-time is ending. If the user want to prolong the reading, he/she can earn another half-hour of light by pushing on P1. Turning-off the lamp at users ease is obtained by pushing on P2.

Circuit Diagram:

A Bedside Lamp Timer Circuit Diagram

Parts:
Resistors
R1 = 1K
R2 = 4K7
R3 = 10M
R4 = 1M
R5 = 10K

Capacitors
C1 = 470µF-25V
C2-C4100nF-63V

Semiconductors
C1 = 470µF-25V
C2-C4 = 100nF-63V
D1-D4 = 1N4002
D5 = 5mm. Red LED
IC1 = CD4012
IC2 = CD4060
Q1 = BC328
Q2 = BC547

Miscellaneous
P1,P2 = SPST Pushbuttons
T1 = 9+9 Volt Secondary 1VA Mains transformer
RL1 = 10.5V 470 Ohm Relay with SPDT 2A 220V switch
PL1 = Male Mains plug
SK1 = Female Mains socket

Circuit operation:

Q1 and Q2 form an ALL-ON ALL-OFF circuit that in the off state draws no significant current. P1 starts the circuit, the relay is turned on and the two ICs are powered. The lamp is powered by the relay switch, and IC2 is reset with a positive voltage at pin 12. IC2 starts oscillating at a frequency set by R4 and C4. With the values shown, pin 3 goes high after around 30 minutes, turning off the circuit via C3. During the c6 minutes preceding turn-off.

The LED does a blinking action by connections of IC1 to pins 1, 2 & 15 of IC2. Blinking frequency is provided by IC2 oscillator at pin 9. The two gates of IC1 are wired in parallel to source more current. If required, a piezo sounder can be connected to pins 1 & 14 of IC1. Obviously, timings can be varied changing C4 and/or R4 values.

Source : www.extremecircuits.net

Circuit Diagram:

 Active High Pass Filter Circuit Diagram

This is active high pass filter circuit for 327Hz frequency using LM741. It will use to build Harmonic at 3 of 130.81 frequency have the value at least. More than the frequency Fundamental 30 dB, for output be sawtooth wave form for use in sound of music way system Electronic design will use the circuit filters three rank frequency. By have 3 dB you slopes can use Op-amp IC number LM741 or number LF351it will meet the frequency well.

Source: ElecCircuit