Circuit described here is a four channel audio distribution amplifier. The input and all four outputs may be connected through the XLR jacks. The input accepts a balanced. Each of the four outputs provides line level balanced signal. On board Trimport provided to adjust the gain of each output channel and also Master gain adjust for input signal, Trim-pot can be replaced with 16mm Potententiometer, circuit required dual15 V DC supply (+/-15V DC). Circuit designed using low noise BA4560 Op-amp from ROHM.

Download PDF Document


  • Supply +/-15V DC (Dual 15V DC)
  • 4 Balanced Outputs Male XLR Connectors
  • 1 Balanced Input Female XLR Connector
  • 4 Trimmer-Pots (Output Gain Adjust)
  • 1 Trimmer-Pot (Master Input Gain Adjust)

Low Noise Dual Supply Voltage Operational Amplifier – BA4560

General-purpose BA4560 op-amp is suitable for any audio applications due to low noise and low distortion characteristics and are usable for other many applications by wide operating supply voltage range. BA4560R is high-reliability products with extended operating temperature range and high ESD tolerance.

Arduino 4 Channel Infra-Red Remote Controlled ON/OFF Switch

The project published here allows turning ON and OFF  lights fans using infra red remote.  Project consist 4 channel Nano relay shield, low cost infra-red remote.  The project can control Fan, AC lamps AC230V/AC110V or DC load upto 7Amps.


  • Supply 12V DC
  • Current consumtion 250mAmps ( When All Relays are in On State)
  • Relay Switch Load 7Amps AC /DC

Arduino Pins

  • 4 Relay: Arduino Pin D2, D3, D4, D5
  • Infra-Red Receiver TSOP1838: Arduino Pin D6

Arduino Code Github

Download Arduino Code

Download PDF Schematic

Download Infra Red Library

Decoding the IR code is important to pair any Infra-Red transmitter with the receiver, check bellow link to understand the decoding of IR signal from various infra-red remote protocols.

How to Setup the IR Remote ( Link)

Adafruit Receving and Decoding Infra Red Code (Link)

Infra-Red Code Decoder (Arduino Code)

#include <IRremote.h>

int IRPIN = 6;

IRrecv irrecv(IRPIN);

decode_results result;

void setup()
Serial.println(“Enabling IRin”);
Serial.println(“Enabled IRin”);

void loop()
if (irrecv.decode(&result))
Serial.println(result.value, HEX);

Arduino Code – 4 Channel IR Remote Controlled  On/Off Switch

* 4 Channel Arduino Infra Red Remote Controller with Relay
* Circuit diagram, PCB Layout and Arduino Code available on our website
* Code Author Ken Shirriff


#include <IRremote.h>

int RECV_PIN = 6;
String IRButton1 = “FD20DF”;//SWITCH 1
String IRButton2 = “FDA05F”;//SWITCH 2
String IRButton3 = “FD609F”;//SWITCH 3
String IRButton4 = “FD10EF”;//SWITCH 4
const int ledPin1 = 2;// Relay 1
const int ledPin2 = 3;// Relay 2
const int ledPin3 = 4;// Relay 3
const int ledPin4 = 5;// Relay 4

IRrecv irrecv(RECV_PIN);

decode_results results;
int button1 = 0;
int button2 = 0;
int button3 = 0;
int button4 = 0;

void setup()
irrecv.enableIRIn(); // Start the receiver
pinMode(ledPin1, OUTPUT);
pinMode(ledPin2, OUTPUT);
pinMode(ledPin3, OUTPUT);
pinMode(ledPin4, OUTPUT);

void loop() {
if (irrecv.decode(&results)) {
Serial.println(results.value, HEX);
BUTTONPRESSED = String(results.value, HEX);
Serial.print(“BUTTONPRESSED “);

//button 1
if (BUTTONPRESSED == IRButton1) {
if (button1 == 0) {
button1 = 1;
button1 = 0;
if (button1 == 1) {
digitalWrite(ledPin1, HIGH);

digitalWrite(ledPin1, LOW);

//button 2
if (BUTTONPRESSED == IRButton2) {
if (button2 == 0) {
button2 = 1;
button2 = 0;
if (button2 == 1) {
digitalWrite(ledPin2, HIGH);

digitalWrite(ledPin2, LOW);

//button 3
if (BUTTONPRESSED == IRButton3) {
if (button3 == 0) {
button3 = 1;
button3 = 0;
if (button3 == 1) {
digitalWrite(ledPin3, HIGH);
digitalWrite(ledPin3, LOW);

//button 4
if (BUTTONPRESSED == IRButton4) {
if (button4 == 0) {
button4 = 1;
button4 = 0;
if (button4 == 1) {
digitalWrite(ledPin4, HIGH);
digitalWrite(ledPin4, LOW);

irrecv.resume(); // Receive the next value


Arduino 4 channel on-off (toggle) switch

Arduino based 4 channel toggle switch using 4 relays, 4 tactile switches, an Arduino Nano, the circuit required 12V DC, the relay can handle load up to 7Amps 230V DC or 7Amps/30V DC.

Download Arduino Code

Download PDF Schematic

Download Code>>>> Github




int SWITCH1 = A3;
int SWITCH2 = A4;
int SWITCH3 = A5;
int SWITCH4 = 7;

int RELAY1 = 5;
int RELAY2 = 4;
int RELAY3 = 3;
int RELAY4 = 2;

//States for RELAY-1 and SWITCH-1

int state1 = HIGH; // the current state of the output pin
int reading1; // the current reading from the input pin
int previous1 = LOW; // the previous reading from the input pin

//States for RELAY-2 and SWITCH-2

int state2 = HIGH; // the current state of the output pin
int reading2; // the current reading from the input pin
int previous2 = LOW; // the previous reading from the input pin

//States for RELAY-3 and SWITCH-3

int state3 = HIGH; // the current state of the output pin
int reading3; // the current reading from the input pin
int previous3 = LOW; // the previous reading from the input pin

//States for RELAY-4 and SWITCH-4

int state4 = HIGH; // the current state of the output pin
int reading4; // the current reading from the input pin
int previous4 = LOW; // the previous reading from the input pin

// the follow variables are long’s because the time, measured in miliseconds,
// will quickly become a bigger number than can be stored in an int.
long time1 = 0; // the last time the output pin was toggled
long time2 = 0;
long time3 = 0;
long time4 = 0;

long debounce1 = 200; // the debounce time, increase if the output flickers
long debounce2 = 200;
long debounce3 = 200;
long debounce4 = 200;

void setup()
pinMode(SWITCH1, INPUT);
pinMode(SWITCH2, INPUT);
pinMode(SWITCH3, INPUT);
pinMode(SWITCH4, INPUT);

pinMode(RELAY1, OUTPUT);
pinMode(RELAY2, OUTPUT);
pinMode(RELAY3, OUTPUT);
pinMode(RELAY4, OUTPUT);


void loop() {

reading1 = digitalRead(SWITCH1);
reading2 = digitalRead(SWITCH2);
reading3 = digitalRead(SWITCH3);
reading4 = digitalRead(SWITCH4);

// if the input just went from LOW and HIGH and we’ve waited long enough
// to ignore any noise on the circuit, toggle the output pin and remember
// the time
//Condition Relay 1
if (reading1 == HIGH && previous1 == LOW && millis() – time1 > debounce1) {
if (state1 == HIGH)
state1 = LOW;
state1 = HIGH;

time1 = millis();

//Condition Relay 2
if (reading2 == HIGH && previous2 == LOW && millis() – time2 > debounce2) {
if (state2 == HIGH)
state2 = LOW;
state2 = HIGH;

time2 = millis();

//Condition Relay 3
if (reading3 == HIGH && previous3 == LOW && millis() – time3 > debounce3) {
if (state3 == HIGH)
state3 = LOW;
state3 = HIGH;

time3 = millis();

//Condition Relay 4
if (reading4 == HIGH && previous4 == LOW && millis() – time4 > debounce4) {
if (state4 == HIGH)
state4 = LOW;
state4 = HIGH;

time4 = millis();

digitalWrite(RELAY1, state1);
digitalWrite(RELAY2, state2);
digitalWrite(RELAY3, state3);
digitalWrite(RELAY4, state4);

previous1 = reading1;
previous2 = reading2;
previous3 = reading3;
previous4 = reading4;

Multi-Output Power Supply (Output 12V, 5V, 3.3V, 1.2V to 10V)

The multi-output power supply is a very useful project for hobbyist, the small module provides 12V, 5V, 3.3V, and 1.2 V to 10V adjustable from 15V  to 30V 3A DC input. If you have a spare laptop power adapter can help as an input power source. Can power many Arduino projects. The project has been designed using LM2576ADJ, LM317-ADJ Regulator.


  • Output 1:  12V 1.5Amp
  • Output 2:  5V-500mA
  • Output 3  3.3V-500mA
  • Output 4:  1.2V-10V 500mA
  • Input 15V-30V DC OR DC Jack for Laptop SMPS 19V DC (3Amps)

Download PDF PCB Layout

Gerber File for This Project Available On Request

Schematic LM2576ADJ, LM317-ADJ

Arduino Nano 4 Channel Relay Shield

The Relay Shield is a module with 4 mechanical relays that provides you an easy way to control high voltage using Arduino Nano. 4 Channel Relay Arduino Nano shield contains onboard 4 relays, TSOP1838 Infra-Red Sensor, NRF24L01 RF transceiver module, 4tactile switches.  The circuit described here can be used for many applications like the infra-red remote controller, RF remote controller, 4 channel toggle switch.

Download PDF Document


  • Supply 12V DC
  • 4 Relay with Normally Open/ Normally Closed Switch
  • The relay can handle 7Amps 230V AC or 30V DC
  • On-Board TSOP1838 Infra-Red Receiver
  • On Board 4 Tactile Switches
  • On-Board NRF24L01 RF Module



Hi-End Headphone Amplifier for DACs Differential Signal input

Simple stereo headphone amplifier for audio DACs required a differential signal. The circuit works with dual +/-5V DC supply, the project can drive load 16 Ohms to 600 Ohms. Headphone amplifier provides output 50mW into 32 Ohms. Signal for the right channel and left channel input is applied to the amplifier through connectors CN1and CN3, respectively. The source such as an audio analyzer or audio digital-to-analog converts (DAC). The positive input from the source connects to the pin labeled I1+/I2+, the negative input from the source connects to the pin labeled I1-/I2-, and the ground connection from the source connects to the center pin of CN1 and CN3, labeled GND. Output connections are provided through the use of the CN2, CN4 provided to power up the board, D1 power LED. OPA1688 or OPA1622 op-amps are good for the applications.

Download PDF Document


  • Supply Input +/-5V DC
  • Load 16 Ohms to 600 Ohms (32 Ohms Ideal)
  • Output Load 50mW into 32 Ohms Headphone
  • Frequency Response 20 Hz to 20 kHz

3 Amps power operational amplifier using lm675

Power operational board can drive high current load up to 3Amps, the board helpful to drive Dc Motor, solenoid, Lamp, LED and industrial application. The project built around LM675 power op-amp from texas instruments. All resistors are 1%. Refer datasheet of LM675 for further information.

I Output= VIN X 2.5amps/volt

i.e Iout=1A when VIN=400mV

Trimmer Pot for Max Rout

Download PDF PCB Layout

The LM675 is a monolithic power operational amplifier featuring wide bandwidth and low input offset voltage, making it equally suitable for AC and DC applications.

The LM675 is capable of delivering output currents in excess of 3 amps, operating at supply voltages of up to 48V. The device overload protection consists of both internal current limiting and thermal shutdown. The amplifier is also internally compensated for gains of 10 or greater.


  • 3A Current Capability
  • AVO Typically 90 dB
  • 5 MHz Gain Bandwidth Product
  • 8 V/μs Slew Rate
  • Wide Power Bandwidth 70 kHz
  • 1 mV Typical Offset Voltage
  • Short Circuit Protection
  • Thermal Protection with Parole Circuit (100% Tested)
  • 16V–48V Supply Range ( +/-12 To 24V DC)
  • Wide Common-Mode Range
  • Internal Output Protection Diodes
  • 90 dB Ripple Rejection


Original Circuit from Texas Instruments Data Sheet

1 2 3 55