Optical Reflective Line Sensor for Robotics and No Contact Surface Sensing QRE1113

The sensor circuit helps to sensing the line for robotics application and  no contact surface sensing. The mini line sensor provides analog voltage output and can work with 3.3V and 5V DC. Analog output voltage is proportional to IR reflected to the senor. Resistor R1 controls the current  to IR LED, R2 provided as pull up resistor. Sensor contains Infra-Red led and photo transistor detector.

Download PDF Schematic


Schematic Line Sensing Sensor QRE1113



PCB layout QRE1113 Optical Sensor




Pin Configuration

10 LED Bar-Graph Display- 10 Segment Bar-Graph Voltmeter Arduino Nano

Turns on a series of 10 Segments of LEDs based on the value of an analog sensor. This is a simple way to make a bar graph display. This method can be used to control any series of digital outputs that depends on an analog input. Trimmer Potentiometer and Analog joystick used to test the code.


  • 10 3MM LEDs
  • 470 E Series Resistor to limit the current to LED
  • 5K Ohms Trimmer Potentiometer/10K Joystick used to test the code


Video Available Here







Arduino Code 10 LED Bar-Graph Display / Bar-Graph 5 Voltmeter 

LED bar graph

Turns on a series of LEDs based on the value of an analog sensor.
This is a simple way to make a bar graph display. Though this graph uses 10
LEDs, you can use any number by changing the LED count and the pins in the

This method can be used to control any series of digital outputs that depends
on an analog input.

The circuit:
– LEDs from pins D2 through D11 to ground
-Trimmer Potentiometer 5K on A0


// these constants won’t change:
const int analogPin = A0; // the pin that the potentiometer is attached to
const int ledCount = 10; // the number of LEDs in the bar graph

int ledPins[] = {
2, 3, 4, 5, 6, 7, 8, 9, 10, 11
}; // an array of pin numbers to which LEDs are attached

void setup() {
// loop over the pin array and set them all to output:
for (int thisLed = 0; thisLed < ledCount; thisLed++) {
pinMode(ledPins[thisLed], OUTPUT);

void loop() {
// read the potentiometer:
int sensorReading = analogRead(analogPin);
// map the result to a range from 0 to the number of LEDs:
int ledLevel = map(sensorReading, 0, 1023, 0, ledCount);

// loop over the LED array:
for (int thisLed = 0; thisLed < ledCount; thisLed++) {
// if the array element’s index is less than ledLevel,
// turn the pin for this element on:
if (thisLed < ledLevel) {
digitalWrite(ledPins[thisLed], HIGH);
// turn off all pins higher than the ledLevel:
else {
digitalWrite(ledPins[thisLed], LOW);



L298 Dual/Single DC Motor Driver Shield Arduino Nano

Dual Motor L298 H-Bridge Control project can control two DC motors OR single motor with 2X current. The circuit is designed around popular dual H-Bridge L298 from ST. This board can be configured to drive a single motor with high current rating also. This can be achieved with the help of jumpers on the board. An onboard 5V regulator can take a maximum of 18V of DC input. Should you wish to drive this board with higher voltage then 18V, you will need to connect a external 5V regulated source to the logic circuit. For this you will need to remove J-5V. This board can fit in any small toy or robot due to small size and very low profile. L298 IC is mounted under the PCB in horizontal position to make board small and low profile to fit any small robot. On board 5V regulator can be used to power up external Micro-Controller board as well as internal logic supply.




Motor supply: 7 to 46 VDC
Control Logic Input: Standard TTL logic level
Output DC drive to motor: up to 2 A each (Peak)
On Board 5V Regulator (Close J-5V to Use On Board 5V Regulator)
Enable and direction control pins available
External Diode Bridge for protection
Heat-sink for IC
Power-On LED indicator
Header Connector for Inputs and PWM
On Board PCB Solderable Jumpers for Enable
Screw terminal connector for easy input supply (PWR) / output (Motor) connection


L298 to Arduino Nano Connections>I1>D4,I2>D5,E1>D6,I3>D9,I4>D10,E2>D11




4 Channel Relay Driver Shield For Arduino Nano



Quad Channel Relay Board Arduino Nano Shield is a simple and convenient way to interface 4 relays for switching application in your project.


     Input supply 12 VDC @ 170 mA

     Output four SPDT relay

     Relay specification 5 A @ 230 VAC

     Trigger level 2 ~ 5 VDC from Arduino I/O D2,D3,D4,D5 Digital Lines

     Power Battery Terminal (PBT) for easy relay output and aux power connection

     LED on each channel indicates relay status

Applications: Robotics, Electronics projects, Industrial controls, Microwaves Oven, Fans, DC Motor, AC Lamp, Solenoids Remote Controls etc.

Relay Load (Contact Capacity of Relay)


  •     7 A @ 230-250 VAC
  •     10 A @ 120 VAC
  •     10 A @ 24 VDC
  •     CN1 – CN4 Connector : Relay 1 to 4 (S1 to S4) Output (Normally Open/Normally Close)
  •     CN5 Connector : Control Signal Input, Trigger 2 to 5 VDC and Supply Input 12 VDC
  •     D2,D4,D6,D8 : Relay On/Off LED Indication
  •     CN6 , CN7 12V DC Input





Universal Dual Op-Amp Development PCB & Schematic using THT Components

The Universal Op-Amp Development board is a general purpose blank circuit boards that simplify prototyping circuits for a variety of Op-Amp circuits. The evaluation module board design allows many different circuits to be constructed easily and quickly.

Universal Dual Operational Amplifier (Op-Amp) board is designed to aid in the evaluation and testing of the low voltage/low power and some precision operational amplifiers. This board will accommodate Dual op amp that are assembled in a 8 Pin Dip package. This board is designed to use single or dual amplifiers. Many different circuits can be made such as inverting, non-inverting, differential-In amplifiers and low-pass, band-pass, band reject, or notch second order filters. The amplifier can be powered with single or dual supplies. These circuits can be configured without any modifications to the board, all that is necessary is to select the correct resistors and capacitors. The other optional components can be left open or shorted depending on the configuration desired.

Power is applied to the Header connector pins labeled VCC,-VEE, GND, If a single supply is used, then -VEE should be connected to GND.

This board mainly support lots of Texas instruments Op-Amps, On Semi, Analog Devices

List Of Op-Amps Can be use

  • OPA2350
  • OPA2340
  • LM358
  • LF422






Inverting Operational Amplifier Circuit ( Universal Op-Amplifier Development Board)

This is most widely used operational amplifier circuit.  It is an amplifier whose closed-loop gain is set by R27 & R18. It can amplify AC or DC Signal.

Non Inverting Operation Amplifier ( Universal Op-Amplifier Development Board)

This simple circuit is a non-inverting Operation Amplifier can be made using universal Op-Amplifier Development Board. Output voltage has same phase as the input voltage ( For DC Input)


What is STEM

Science + Technology + Engineering + Math

STEM encompasses fields that are collectively considered the core technological underpinnings of an advanced society. Co-founders, Melissa and Lavanya, are mechanical engineers with a passion for promoting STEM literacy for all. They believe in exciting students about STEM through fun, hands-on experiences where real learning occurs.