Switching Regulator 3A

 

When compared to linear voltage regulators the switching voltage regulators are much
power efficient. In the case of linear voltage regulators the difference between the
input and output voltage is just wasted and for switching regulators there is almost no
such wastage and that’s why the switching regulators have great power efficiency ranging
up to 85% . In simple words, the switching regulator operates by taking small bits of
energy from the input voltage source and then transferring it to the output with the
help of a solid state switch and a control circuitry. Since the switching element is
either fully open or closed at any moment, no energy is wasted  across it. The control
circuit controls  the duty cycle of the solid state switch which in turn determines rate
at which energy is transferred to the output.
The electronic circuit given here is of a simple and low cost switching regulator using
the IC LM317 that can deliver up to 3A of current. The input voltage range of this
circuit is between 8 to 35V DC and the output voltage can be adjusted between 1.8 to 32V
DC. The output voltage can be adjusted by using the POT R
Notes.
Assemble the circuit on a good quality PCB.
C4 and C3  must be a solid tantalum capacitor.
Transistor T1 and IC1 require heat sinks.
L1 can be a 600uH inductor.

source: http://www.circuitstoday.com

20 Watt Amplifier & Voltage Level Detektor

This is just another 20W audio amplifier circuit , but this time based on the LM1875 audio amplifier IC from National Semiconductors. With a 25V dual power supply LM1875 can deliver 20W of audio power into a 4 ohm speaker. The LM1875 requires very less external components and has very low distortion. The IC is also packed with a lot good features like fast slew rate, wide supply voltage range, high output current, high output voltage swing, thermal protection etc. The IC is available in TO-220 plastic power package and is well suitable for a variety of applications like audio systems, servo amplifiers, home theatre systems etc.source :circuitstoday.com.

The circuit as explained by Rakesh:

The design came from the interest of finding a new technique of analog to digital conversion. The two types of ADC (Analog to Digital Converter) that inspired me in the development of this circuit are Flash Type ADC and Successive Approximation Type ADC.  The Flash Type ADC is the fastest ADC available in the market (highest sampling rate 120 Msps) but it uses a huge number of OP-AMPS. On the other hand Successive Approximation Type ADC uses fewer components but its speed is dependent upon the clock frequency provided to it. I was looking for a technique that can give a trade-off between this two, the result of which is this circuit.
Construction
The working of this circuit is similar to that of decimal fraction to binary fraction conversion. For this purpose, the circuit amplifies a signal and compares it to a reference voltage. The circuit can be divided into a number of stages. Number of stages can be increased or decreased according to need. Each stage contains two OP-AMPs(TL084).  One of them (OP-AMP at the left side) is used for comparison purpose. The other (OP-AMP at the right side) is used as a non-inverting amplifier with a fixed gain (EXACTLY 2). The input voltage is connected to the non-inverting pin/terminal of each OP-AMP. The digital output is obtained from the output of the comparing OP-AMP and the output of the amplifier OP-AMP is fed to the input of the next stage. To obtain a reference voltage, two resistors are used.
Working
An input voltage is applied. The OP-AMP used as a comparator compares the input voltage with the reference level. If it exceeds a certain reference level, the comparator output goes high and there is amplification along with subtraction operation is performed by the amplifying OP-AMP. If the input voltage is less than the reference voltage, only the amplification operation is performed. The output of the amplifier OP-AMP is inherited to lower stages.
The output of my interest is the outputs obtained from the comparator OP-AMPs. They together represent binary number.source :circuitstoday.com

Crossover Active Circuit

Crossover circuits are of two types, active and passive. Passive crossover circuit uses passive components only and they are very simple, but they waste a considerable amount of energy and also induce distortion. Active crossovers does not have the above said draw backs and they are a better option for HiFi audio systems. Active crossovers split the incoming complex audio signal into to two bands, a low frequency out and a high frequency out. These two bands a separately amplified by two power amplifier stages, one tuned to the low frequency band and the other tuned to high frequency stage respectively (bi-amping).
The cross over circuit given here uses LM833 National Semiconductors. LM833 is a dual operational amplifier especially designed for audio applications. The circuit requires four opamps and so two LM833 ICs are used here. The circuit can be divided into two parts, a high pass filter section and a low pass filter section. IC2b forms a first order Butterworth low pass filter circuitry and the low frequency out is available at its output pin (pin1). The high frequency out is available at pin 7 of IC1a. For the given components crossover frequency is 1KHz and it is according to the equation Fc = 1/(2pRC).

source: http://www.circuitstoday.com

Ni-MH battery charger

This is the circuit diagram of a very powerful and efficient Ni-MH battery charger using IC LT4060 from Linear Technologies. In addition to Ni-MH batteries Ni-Cd batteries can be also charged by slightly modifying the circuit.For charging Ni-Cd batteries connect the CHEM pin (pin12) of the IC to +Vcc.Here the circuit is configured to charge 2 cells connected in series. By altering the connections of SEL0 and SEL1 pins, upto 4 batteries in series can be charged using this circuit. For charging a  single cell, connect SEL0 and SEL1 pins to GND. For charging two cells, connect SEL1 to GND and SEL0 to Vcc. For charging  three cells,  connect SEL1 to VCC and SEL0 to GND. For charging 4 cells, connect SEL0 and SEL1 pins to VCC. The circuit also features temperature based charge qualification.An NTC thermistor connected at the NTC pin (pin11) of the IC serves as the temperature sensor.

source: http://www.circuitstoday.com

Tachometer Circuit

ENGLISH  and  INDONESIAN
>< Here is a simple circuit that can be used as a tachometer. The circuit is basically a frequency to current converter which converts the incoming signal into a proportional current to drive the meter. The deflection on the ammeter will be proportional to the frequency of the incoming signal. For using this circuit as an automobile tachometer, the input terminal A should be connected to the spark plug cable and terminal B should be connected to the vehicles ground.
For calibrating the circuit, set R2 at 25K and R4 at 5K.Power up the circuit and feed the input terminal with a 60Hz square wave form your function generator. Adjust R2 so that the meter shows 0.36 mA (equal to 3600rpm). Now disconnect the input signal and adjust R3 so that the meter shows 0mA.Now connect the 60Hz signal again and if the meter does not show 0.36mA adjust R4.A completely calibrated circuit will show 0mA at 0Hz and 0.36mA at 60Hz.

>< Berikut adalah rangkaian sederhana yang dapat digunakan sebagai sebuah tachometer. Rangkaian ini pada dasarnya frekuensi untuk konverter arus yang mengubah sinyal yang masuk ke arus proporsional untuk mendorong meter. Defleksi pada ammeter akan sebanding dengan frekuensi dari sinyal yang masuk. Untuk menggunakan rangkaian ini sebagai tachometer mobil, terminal masukan A harus dihubungkan ke kabel busi dan terminal B harus terhubung ke tanah kendaraan.Untuk mengkalibrasi rangkaian, set R2 pada 25K dan R4 pada 5K.Power atas sirkuit dan pakan terminal input dengan bentuk gelombang persegi 60Hz fungsi generator Anda. Sesuaikan R2 sehingga meter menunjukkan 0,36 mA (sama dengan 3600rpm). Sekarang lepaskan sinyal input dan menyesuaikan R3 sehingga meter menunjukkan 0mA.Now menghubungkan sinyal 60Hz lagi dan jika meter tidak menunjukkan 0.36mA menyesuaikan sirkuit R4.A sepenuhnya dikalibrasi akan menunjukkan 0mA di 0Hz dan 0.36mA pada 60Hz.

source: http://www.circuitstoday.com

Update Terbaru

This circuit can be used to test whether mains voltage is present or not without having electric contact with mains line. The CMOS IC CD4033 is the heart of this circuit. The CD4033 consists of a 5 stage decade Johnson counter and an output decoder for converting the Johnson code to a 7 segment decoded output for driving 7 segment LED display.READ MORE...

Power saving LED lamp from your scrap box.
This circuit is designed by Mr Seetharaman Subramanian and we are very glad to publish it here. In this article he is showing a method to convert a broken/defunct CFL into a LED based power saving light.READ MORE...
 Here is a very useful lamp flasher circuit using the famous adjustable voltage regulator IC LM317T. LM317 can source up to 1A of current and so up to 12W lamps can be used with this flasher. Such a circuit finds huge application in automobiles.READ MORE...

This is a simple and easy to construct digital dice circuit. The circuit is based on a single IC, CD4060B.The dice consists of six LEDs marked D1 to D6.The number of LEDs glowing indicates the numeral.READ MORE...

Here is a simple dancing light circuit based on NE555 (IC1) & CD4017 (IC2) .The IC1 is wired as an astable multivibrator to provide the clock pulses for the CD4017.

READ MORE...

Power Saving Led Lamp

Power saving LED lamp from your scrap box.
This circuit is designed by Mr Seetharaman Subramanian and we are very glad to publish it here. In this article he is showing a method to convert a broken/defunct CFL into a LED based power saving light.
The  is just a LED lamp circuit that can be operated from the mains voltage. A string of five LED is driven using a capacitive transformer less power supply. In the circuit 0.47uF/400V Polyester capacitor C1 reduces the mains voltage. R1 is a bleeder resistor which drains the stored charge from C1 when the AC input is switched OFF. Resistors R2 and R3 limits the inrush of current when the circuit is switched ON. Diodes D1 to D4 forms a bridge rectifier that rectifies the reduced AC voltage and C2 acts as a filter capacitor. Finally Zener diode D1 provides regulation and the LEDs are driven.

source: www.circuitstoday.com

Tester Voltage Circuit

 

This circuit can be used to test whether mains voltage is present or not without having electric contact with mains line. The CMOS IC CD4033 is the heart of this circuit. The CD4033 consists of a 5 stage decade Johnson counter and an output decoder for converting the Johnson code to a 7 segment decoded output for driving 7 segment LED display. A 10cm long insulated copper wire connected to the clock pin (pin1) of the IC serves as the sensor. The sensor wire has to be placed in the vicinity of the mains wire to be tested. When there is no voltage in the mains line, no voltage will be induced in the sensor wire and the display will show a random digit. When there is voltage in the mains line, a small voltage will be induced in the sensor wire due to electromagnetic induction and this voltage is sufficient enough to clock the CMOS IC CD4033. Now the display will count from zero to nine and repeat.
Circuit diagram.
Notes.
The circuit can be assembled on a Vero board.
Use 9V PP3 battery for powering the circuit.
Use a 10cm insulated wire as the sensor.
The IC must be mounted on a holder.
Switch S1 can be a miniature ON/OFF switch

source: http://www.circuitstoday.com/

Lampu Flash LM317

Here is a very useful lamp flasher circuit using the famous adjustable voltage regulator IC LM317T. LM317 can source up to 1A of current and so up to 12W lamps can be used with this flasher. Such a circuit finds huge application in automobiles. The frequency of the flashing depends on the value of resistors R1 to R3 and capacitors C2 to C4.With the given values; the flashing rate is around 5 flashes per second.
Circuit diagram.
Notes.
The circuit can be assembled on a Vero board.
Use 12V DC for powering the circuit.
Use a proper heat sink with the IC1

Read more: http://www.circuitstoday.com/lamp-flasher-using-lm317#ixzz1PqKIZZXd

Dancing Light

 

Here is a simple dancing light circuit based on NE555 (IC1) & CD4017 (IC2) .The IC1 is wired as an astable multivibrator to provide the clock pulses for the CD4017.For each clock pulse receiving at the clock input (pin14) of IC CD4017, the outputs Q0 to Q9 (refer pin diagram of CD 401) becomes high one by one alternatively.The LEDs connected to these pins glow in the same fashion to give a dancing effect.The speed of the dancing LEDs depend on the frequency of the clock pulses generated by the IC1.
Circuit diagram with Parts list.
Notes.
Assemble the circuit on a good quality PCB or common board.
The ICs must be mounted on holders.
The speed of the dancing LEDs can be adjusted by varying POT R2.
The capacitor C1 must be rated 15V.
Using different color LEDs could produce a better visual effect

source: http://www.circuitstoday.com

Digital Dice Light

This is a simple and easy to construct digital dice circuit. The circuit is based on a single IC, CD4060B.The dice consists of six LEDs marked D1 to D6.The number of LEDs glowing indicates the numeral.
The heart of this circuit is 14 stage binary ripple counter IC CD4060B.The IC also has a built-in oscillator. The oscillator output (here 2 KHz) is used to clock the binary ripple counter. The counter increments by one in its natural count sequence each time it is clocked. The oscillator in initially inhibited as long as the pushbutton switch S2 is not pressed. The counter outputs will be in logic zero state and all the six LEDs will be ON.As the push button S2 is pressed, oscillator is enabled and the counter starts counting. The counter outputs (pin 4, 5 & 7) changes from 000 to 101 and then resets to 000 to repeat the sequence. After 101 the counter does not advances to 110 because of R3, D7 & D8.When the counter just advances from 101 to 110 the diodes D7 & D8 become reverse biased and makes the reset pin (pin 12) high to reset the counter.
The counter counts as long as the push button switch S2 is pressed. Also the micro buzzer will sound as long as the IC is counting. When the push button switch S2 is released, the counting is stopped and holds the existing state to represent the random number.Circuit diagram with Parts list.
Notes.
Switch S1 is the ON/OFF switch.Switch S2 can be a push button switch.Buzzer K1 is a piezo buzzer.The circuit can be powered from a 9V PP3 battery.The IC must be mounted on a holde

source: http://www.circuitstoday.com

Battere Charger 24 volt

This lead acid battere charger circuit is designed in response to a request from

Mr.Devdas .C. His requirement was a circuit to charge two 12V/7AH lead acid batteries in

series.Anyway he did not mentioned the no of cells per  each 12V battery. The no of

cells/battery is also an important parameter and here I designed the circuit assuming 

each 12V battery containing 6 cells. When two batteries are connected in series, the

voltage will add up and the current capacity remains same. So two 12V/7AH batteries

connected in series can be considered as a 24V/7AH battery.

The circuit given here is a current limited lead acid battery charger built around the

famous variable voltage regulator IC LM 317. The charging current depends on the value

of resistor R2 and here it is set to be 700mA. Resistor R3 and POT R4 determines the

charging voltage. Transformer T1 steps down the mains voltage and bridge D1 does the job

of rectification. C1 is the filter capacitor. Diode D1 prevents the reverse flow of

current from the battery when charger is switched OFF or when mains power is not available.

Notes.

Assemble the circuit on a good quality PCB.

T1 can be a 230V primary, 35V/3A secondary step down transformer.

If 3A Bridge is not available, make one using four 1N5003 diodes.

LM317 must be fitted with a heat sink.

R2 = 0.85 ohm  is not a standard value. You can obtain it by combining a 6.2 ohm and 1

ohm resistors in parallel.

F1 can be a 2A fuse.

To setup the charging voltage, power ON  the charger and hook up a voltmeter across the

output terminals and adjust R4 to make the voltmeter read 28V. Now the charger is ready

and you can connect the batteries.

This charger is specifically designed for two 12V/7AH/6 cell lead acid batteries  in

series OR a  24V/7AH/12 cell lead acid battery.

Read more: http://www.circuitstoday.com/24v-lead-acid-battery-charger-circuit#ixzz1Pls7sC8t

Skema Bel Musik

This circuit produces a musical tone whenever someone touches the touch point designated as TP in the circuit. The circuit works from two AA cells and produces enough sound.
The circuit uses IC UM 3481 commonly used in musical circuits. The IC contains a ROM with 512 musical notes, tone generator, rhythm generator, modulator, run off control, oscillators, frequency divider and preamplifiers,.  So a very few number of components is  required for this circuit.C1 and R1 act as  the timing components for  the built in oscillator. The transistor Q1 is used for driving the loud speaker. The base of the transistor Q2 is used as the touch point to trigger the musical bell.
Notes.
The circuit can be assembled on a general purpose PCB.
Use two AA cells in series for powering the circuit.
The speaker can be 2 W, 8 Ohm.

source circuitstoday.com

Sirine 2 Transistor

Here is the circuit diagram of a simple two transistor alarm circuit that can be operated from a 9V PP3 battery. Here the two transistors are wired to form an oscillator whose frequency increases when switch S2 is pressed and decreases when S2 is released. In order to attain this the base of Q1 is biased from an RC circuit comprising of R2 and C1.When S2 is pressed C1 is charged through the resistor R2.As the voltage across the C1 increases the time constant decreases and this results in an increases in the frequency. When S2 is released capacitor discharges and the frequency of the tone decreases. The sound heard from the speaker will be almost like that of a siren.
Notes.
The circuit can be assembled on a Vero board.
Use a 9V PP3 battery for powering the circuit.
Switch S2 can be a miniature push button switch.
The type no of transistors are not very significant here

Read more: http://www.circuitstoday.com/two-transistor-siren#ixzz1PiqIUanY

UP DOWN counter circuit

UP DOWN counter circuit
    

This is the circuit diagram of a very simple up down counter that can be used of a large number of applications. The circuit is based on the IC CD40110BE which is a CMOS decade up/down counter. For ICs are used here. Common cathode seven segment display is connected to the 7-segment output of each IC.Display connected to the IC1 represents the lowest number and display connected to IC4 represents the largest number. Synchronous counting is achieved by connecting BORROW and CARRY pins of the preceding stage IC to the CLK DOWN and CLK UP of the next stage IC. For UP counting trigger pulse must be given to the pin7 of IC1 and for down counting trigger pulse must be given to the pin9 of IC1.The RESET pins of all IC are shorted and they have to be connected to ground during normal operation. Connecting the RESET pins to positive supply using the  switch S1 resets the counter.
Notes.
The circuit can be powered from a 9V PP3 battery.
All 7 segment displays must be common cathode type.
Resistors R1 to R28 must be 680 Ohm ones.
R29 and R30 can be 10K ones.
Switch S1 can be  a SPDT switch

Read more: http://www.circuitstoday.com/up-down-counter-circuit#ixzz1PiluR9AT

Display 0-9 circuit

Static 0 to 9 display
    

The circuit shown here is of a simple 0 to 9 display that can be employed in a lot of applications. The circuit is based on asynchronous decade counter 7490(IC2), a 7 segment display (D1), and a seven segment decoder/driver IC 7446 (IC1).
The seven segment display consists of 7 LEDs labelled ‘a’ through ‘g’. By forward biasing different LEDs, we can display the digits 0 through 9. Seven segment displays are of two types, common cathode and common anode. In common anode type anodes of all the seven LEDs are tied together, while in common cathode type all cathodes are tied together. The seven segment display used here is a common anode type .Resistor R1 to R7 are current limiting resistors. IC 7446 is a decoder/driver IC used to drive the seven segment display.
Working of this circuit is very simple. For every clock pulse the BCD output of the IC2 (7490) will advance by one bit. The IC1 (7446) will decode this BCD output to corresponding the seven segment form and will drive the display to indicate the corresponding digit.
Notes.
The circuit can be assembled on a perf board.
Use 5V DC for powering the circuit.
The clock can be given to the pin 14 of IC2.
D1 must be a seven segment common anode display.
All ICs must be mounted on holders

Read more: http://www.circuitstoday.com/static-0-to-9-display#ixzz1PinPUJKV

15 Watt Audio Amplifier

The circuit shown here is of a simple Class-B audio amplifier based on opamp TL082,
transistors TIP141 and TIP142. LM833 is a dual opamp with high slew rate and low
distortion particularly designed for audio applications. This audio amplifier circuit
can deliver 15 watt audio output into an 8 ohm speaker at +12/-12V DC dual supply.
Both opamps in the IC are used here. IC1a is wired as a buffer and capacitor C3 does the
job of input DC decoupling. Ic1b is wired in the inverting mode and it provides negative
feedback. Complementary power transistors TIP41 and TIP42 are wired in the Class B push
pull scheme and they drives the loud speaker. Diode D1 provides 0.7V bias voltage for
the push pull pair and capacitor C2 protects the 0.7V bias voltage across D1 from heavy
voltage swings at the IC1b’s output.
Notes :
The audio amplifier circuit must be assembled on a good quality PCB.
Use a holder for mounting IC1.
Use a +12/-12V dual supply for powering the amplifier.
Potentiometer R2 can be used as a volume control.
Raising the power supply voltage will increase the output power. Anyway note the
following points.
TIP42 and 41 can handle only up to 6A.
Maximum supply voltage IC1 can handle is +16/-16 V DC
Read more: http://www.circuitstoday.com/15w-class-b-audio-amplifier#ixzz1PgCb5tTk

Switching regulator dan Step Down circuit

Switching regulator .
   
Switching regulators work by drawing small amounts of energy from the input source and transferring it step by step to the output. This task is attained by using an electronic switch (operating at a predetermined frequency) which works like a gate between the input energy source and the output. This gate controls the amount of charge that is transferred to the output load. The output voltage of the switching regulator depends on how much time the switch is maintained closed. If the OFF time of switch is long then less energy will be transferred to the output load and so the average output voltage will a be low. If the OFF time of switch is short then more energy will be transferred to the output load which results in a better average output voltage.The schematic of a basic switching regulator is shown below.
Schematic of a simplified switching regulator circuit
When switch S1 is closed capacitor Cout is charged and when switch S1 is open the Cout discharges through the load. The duty cycle of the S1 determines how much energy is transferred to the output load. In simple words the capacitor Cout serves as a filter which converts the pulse waveform from the switch in to a steady voltage. The output voltage will be always a function of the input voltage and the duty cycle of the switch.
Schematic of a practical switching regulator
The schematic of a practical switching regulator is shown above. This circuit has two additional components, a Schottky diode D1 and an inductor L1. These two components are present in almost all switching regulator circuits and they drastically improves the performance of the circuit. Let us see how the diode and inductor improves the performance of the regulator circuit.
When switch S1 is closed the inductor L1 opposes the rising current by creating an opposing electromagnetic field and this makes the diode D1 reverse biased and it behaves like an open switch. When switch S1 is made open the electromagnetic field that was induced in the inductor L1 will be discharging and this creates a current in the reverse polarity. This makes the diode D1 forward biased and it will remain in the conducting stage until the field in the inductor becomes zero. In simple words this action is similar to the charging and discharging of the output capacitor. Thus the combined effect of the inductor and diode improves the filtering capability of the output capacitor and so the circuit efficiency is improved.
uA78S40 based switching regulators.
Here are two switching voltage regulator circuits using uA78S40 IC from On Semiconductors. The first one is a step down converter while the second one is an inverting converter.
uA78S40 is a switching regulator IC that can be used for a variety of applications. The uA78S40 is an integrated switching regulator circuit which has built in circuitries for voltage reference with temperature compensation, oscillator with duty cycle control, high capacity switching element, an independent operational amplifier and independent diode. When voltages excess of 40V or output currents excess of 1.5A are required external switching transistors must be used. The features of uA78S40 include wide temperature range, adjustable output voltage (from 1.5V to 40V), peak output current of 1.5A, 80dB load regulation, 80dB line regulation, wide supply voltage range ( from 2.5V to 40V), very low standby current etc. The applications of this IC include step up converters, step down converters, inverting converters etc. The uA78S40 is available in a 16 pin DIP plastic package.

Step down converter circuit.

    
Step down regulator using uA78S40
The circuit shown above is of a switching step down converter using uA78S40. The input voltage can be 25V DC and the output voltage is 5V @500mA. Ct is the timing capacitor for the internal oscillator while C3 is the input filter capacitor.C3 must be rated above 25V while C2 can be rated anything higher than 10V. The instantaneous output voltage (that is the voltage across output capacitor Cc) is fed back to the inverting input of the internal opamp using the resistor network comprising of R1 and R2. R2 and R1 can be used for setting the output voltage. Using the external rectifier diode D1 improves the overall efficiency of the circuit. If you need to use the internal diode of the IC instead of D1 then omit D1 and restore the track shown dotted.

source  www.circuitstoday.com

Dual Power Supply dan inverting convert circuit

Dual supply for this circuit.

   
A  +15V/-15V dual supply for powering this tone control circuit is shown below. Bridge D1 can be made using four 1N4007 diodes.  This supply is unregulated and its quite fine for this circuit. Anyway  if you need to have a regulated one please inform me.
Power supply for tone control circuit
Notes.
Circuit can be assembled on a vero board or perf boad. Any way a PCB is the best option.
Use +15/-15V DC dual supply for powering the circuit.
IC1 TL072 must be mounted on a holder.
By changing the value of R1 and R2 the voltage gain (Av) of the preamplifier stage can be changed

Read more: http://www.circuitstoday.com

Inverting converter circuit.
    
Inverting converter circuit using uA78S40
An inverting converter is a circuit which reverses the polarity of a given input voltage. For example if 5V DC is applied at the input of an inverting converter, the output voltage will be -5V DC. A 15V inverting converter circuit using uA78S40 is shown above. Ct (in the circuit C1) is the timing capacitor for the ICs internal oscillator, C3 is the input filter capacitor and C2 is the output filter capacitor. Both C2 and C3 must be rated at least 25V. Resistors R1 and R2 forms a feedback network which feed backs a portion of the output voltage to the non inverting input of the Ics internal comparator. R2 and R1 can be used to set the output voltage. Transistor Q1 is the external switching transistor. The collector terminals of the internal driver and switching transistors are shorted and connected to the base of the external switching transistor through resistor R3.

Notes.
uA78S40 must be mounted on a holder.
Peak output current of uA78S40 is 1.5A.
1N5822 is a 3A Schottky diode. Do not replace it with an ordinary PN junction diode.
Vout = 1.25 (1+ (R2/R1)) for step down converter.
Vout = (1.25R2) / (R1) for inverting converter.
Switching Regulator Vs Linear regulator.
The controlling element for a linear regulator is an active device ( either a BJT or FET) operating inside its active region.In a linear regulator the difference between the input voltage and output voltage is dissipated as heat by the controlling element. This reduces the power efficiency. The controlling element requires a larger heatsink .

For a switching regulator the controlling element which is an electronic switch (a transistor or thyristor) has only two states, either ON (completely conducting) or OFF (completely open). This means that no power is wasted across the switching element and this result in better power efficiency. A well designed switching regulator can have up to 85% efficiency. The controlling element requires a smaller heatsink.

Tone control circuit

Tone control circuit

   
This is just another circuit designed by Mr. Seetharaman Subramanian and time it is a high quality passive tone control circuit that has an overall gain of around 25 with 20dB boost and cut. This circuit needs minimum number of components, is very cost effective and most of the components required can be found from you junk box. Even though an opamp which is an active element is used in the circuit, the tone control section is entirely passive and that’s why the circuit is named so.
The circuit consists of two parts. Firstly an op-amp based preamplifier stage and secondly a passive Baxandall tone control circuitry. The preamplifier stage is a non inverting amplifier based on TL072. R2 is the feedback resistor which together with resistor R1 sets the gain of this stage and with the stated values it is 23. Voltage gain in the non-inverting mode is expressed using the equation Av= 1+ (R2/R1). Value of R3 (Rin) is taken as approximately equal to the output impedance of TL072. C2 is the input DC decoupling capacitor and it also sets the low frequency cut off limit. R4 is the offset minimizing resistor which reduces the effect of output offset voltage on the output of the amplifier and its value is taken as approximately equal to R1||R2. The preamplifier stage is powered using +15/-15 dual supply. Capacitor C3 couples the preamplifier stage with the tone control stage.
The tone control stage is a passive Baxandall tone control circuit that can produce a 20dB cut or boost. POT R6 is used for controlling the bass while POT R9 can be used for controlling the treble. POT R10 serves as the volume controller while POT R11 can be used to adjust the balance. Resistor R8 provides some isolation between the bass control and treble control stages.
Passive Baxandall tone control circuit: Also known as James Network is a circuit for independently adjusting the bass and treble for high quality audio applications. The circuit is entirely based on passive components and the performance is very superior. In many older passive tone control circuits there was much interaction between the two controls and there was a great deal of asymmetry. Such problems are completely eliminated in Baxandall tone control circuit.
Seetharaman’s words about the circuit: Iam just enclosing you the TL072 (TL062 or 82 also can be used) passive tone control with 20dB boost and cut with a overall gain of around 25. you can also give an overall feedback if required, from output to TL072 inverting input through suitable resistance.

source   www.circuitstoday.com