Type K Thermocouple Sensor Amplifiers with Cold Junction Compensation Using AD595-AD594

The sensor project is based on AD595 IC from Analog devices.  AD595 is a complete instrumentation amplifier and thermo-couple cold junction compensator on a monolithic chip. It combines an ice point reference with a pre-calibrated amplifier to produce a high level (10 mV/°C) output directly from a thermo-couple signal. Pin-strapping options allow it to be used as a linear amplifier-compensator or as a switched output set point controller. It is amplify its compensation voltage directly, thereby converting it to a stand-alone Celsius transducer with a low impedance voltage output. The AD595 includes a thermo-couple failure alarm that indicates if one or both thermo-couple leads become open. The alarm output has a flexible format which includes TTL drive capability.

NOTE : Refer AD595 Data sheet for supply input and other information, The circuit works with single supply, same board also support AD594 IC which can support type J sensor.


  • Supply 15V DC
  • Supports Type K Thermocouples
  • Provides 10 mV/Centigrade

Download PDF Schematic


What is Thermocouple??

A thermocouple is an electrical device consisting of two dissimilar electrical conductors forming electrical junctions at differing temperatures. A thermocouple produces a temperature-dependent voltage as a result of the thermoelectric effect, and this voltage can be interpreted to measure temperature. Thermocouples are a widely used type of temperature sensor

What is Type K Thermocouple Sensor??

Type K Thermocouple (Nickel-Chromium / Nickel-Alumel): The type K is the most common type of thermocouple. It’s inexpensive, accurate, reliable, and has a wide temperature range. Type K thermocouples usually work in most applications as they are nickel based and exhibit good corrosion resistance. It is the most common sensor calibration type providing the widest operating temperature range. Due to its reliability and accuracy the Type K thermocouple is used extensively at temperatures up to 2300°F (1260°C). This type of thermocouple should be protected with a suitable metal or ceramic protection tube, especially in reducing atmospheres. In oxidizing atmospheres, such as electric furnaces, tube protection is not always necessary when other conditions are suitable; however, it is recommended for cleanliness and general mechanical protection. Type K will generally outlast Type J because the JP wire rapidly oxidizes, especially at higher temperatures.

Type K Thermocouple Range

  • Thermocouple grade wire, –454 to 2,300F (–270 to 1260C)
  • Extension wire, 32 to 392F (0 to 200C)


AD595 Output Voltages


Various Type K Temperature Sensors



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);



High Voltage Low EMI Power Supplies for AC Inverters and VF Drives, Brush-Less Motor Drivers

The high voltage high current low EMI, power supply circuit published here is intend use for AC inverters and VF drives,AC servo driver, brushless dc motor driver, IPM (Intelligent Power Module) , high voltage DC brushed motor drivers and various other circuit required high voltage DC supply.   Capacitor has been selected for AC power input up to 250V AC however capacitor voltage and value can be alter as per DC output required.  Bridge rectifier can handle current up to 25Amps and need large heat sink for full load. Onboard transformer used as EMI fliter.

  • AC Supply input up to 250V V AC
  • Maximum DC Output 400V DC and 10Amps.
  • DC Supply Output will depend on input supply
  • Fuse for Short circuit and over current protection
  • Fuse as per your application requirement Maximum 10Amps Fuse
  • NTC provided for inrush current
  • DC Bus has bleeding resistor








Heat Activated Cooling Fan Controller Circuit Using LM393-LM358 & LM35 Temperature Sensor

Heat activated cooling fan controller ( Thermal Activated Cooling Fan Driver Circuit) is a simple project which operates a Brush-Less fan when the temperature in a particular area goes above a set point, when temperature return normal, fan automatically turns off. The project is built using LM358 Op-amp ( Use LM393 instead for good performance) ,  and LM35 temperature Sensor. Project required 12V DC supply and can drive 12V Fan. This project is useful in application like Heat sink temperature controller, PC, heat sensitive equipment, Power supply, Audio Amplifiers, Battery chargers, Oven.

The SMD SO8 LM35 used as temperature sensor, LM358 act as comparator provides high output when temperature rise above set point, high output drive the Fan trough driver transistor. The LM35 series are precision integrated-circuit temperature devices with an output voltage linearly-proportional to the Centigrade temperature. The LM35 device has an advantage over linear temperature sensors calibrated in Kelvin, as the user is not required to subtract a large constant voltage from the output to obtain convenient Centigrade scaling. The LM35 device does not require any external calibration or trimming to provide typical accuracies of ±¼°C at room temperature. Temperature sensing range 2 to 150 centigrade. LM35 provides output of 10mV/Centigrade.

NOTE :  It is  advisable to use LM393 Comparator instead of LM358 as it will provide better results.

  • Supply 12V DC 1Amps
  • Fan 12V DC , 500mA
  • Range : 2 °C to 150 °C
  • Open Collector Output
  • It can drive PC fan
  • Onboard preset to set the Fan trigger level
  • Onboard Power LED
  • Onboard Output LED
  • Output Driver Transistor
  • Header Connector for Supply and Fan
  • PCB dimensions 59.85 mm x 12.70 mm

Watch Video of the project available here







LM35 Temperature Sensor

The LM35 series are precision integrated-circuit temperature devices with an output voltage linearly-proportional to the Centigrade temperature. The LM35 device has an advantage over linear temperature sensors calibrated in Kelvin, as the user is not required to subtract a large constant voltage from the output to obtain convenient Centigrade scaling. The LM35 device does not require any external calibration or trimming to provide typical accuracies of ±¼°C at room temperature and ±¾°C over a full −55°C to 150°C temperature range. Lower cost is assured by trimming and calibration at the wafer level. The low-output impedance, linear output, and precise inherent calibration of the LM35 device makes interfacing to readout or control circuitry especially easy. The device is used with single power supplies, or with plus and minus supplies. As the LM35 device draws only 60 µA from the supply, it has very low self-heating of less than 0.1°C in still air. The LM35 device is rated to operate over a −55°C to 150°C temperature range, while the LM35C device is rated for a −40°C to 110°C range (−10° with improved accuracy). The LM35-series devices are available packaged in hermetic TO transistor packages, while the LM35C, LM35CA, and LM35D devices are available in the plastic TO-92 transistor package. The LM35D device is available in an 8-lead surface-mount small-outline package and a plastic TO-220 package.


LM358 Op-Amp

These devices consist of two independent, high-gain frequency-compensated operational amplifiers designed to operate from a single supply or split supply over a wide range of voltages.

LM393 Comparator

These devices consist of two independent voltage comparators that are designed to operate from a single power supply over a wide range of voltages. Operation from dual supplies also is possible as long as the difference between the two supplies is 2 V to 36 V, and VCC is at least 1.5 V more positive than the input common-mode voltage. Current drain is independent of the supply voltage. The outputs can be connected to other open-collector outputs to achieve wired-AND relationships.

LM293A devices are characterized for operation from −25°C to +85°C. The LM393 and LM393A devices are characterized for operation from 0°C to 70°C. The LM2903, LM2903V,

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





Mini DC Motor Speed and Direction Controller for Low Voltage Motors Using L293D & 555 Timer


Project has been designed around L293 H-Bridge for Bidirectional motor operations, & 555 Timer IC which has been used as PWM generator for speed control. L293 is capable of continuous output current 600mA. Operating voltage 5V DC. Specially designed for low voltage Mini motors. Great control on speed via onboard preset, while direction is controlled by changing jumpers settings. PWM Duty cycle range 20% to 90% . Great kit can be used in science projects, toys, mini motor speed controllers, robotics, model-making.

DC Motor Speed and direction controller project based on L293D H-Bridge and 555 Timer IC. 555 Generate PWM and L293D works as output driver. The 293D provides bidirectional drive current up to 600mA a voltage from 5V to 12V. L293D includes the output clamping diodes for protections.


  • Supply 5 to 12 V
  • Inhibit facility/enable
  • PWM Frequency 5KHz Maximum
  • High Noise immunity
  • Over temperature protection
  • Capable of delivering output current up to 600 mA per channel
  • The control/interface lines are accessible with Berg connector
  • Header connector for motor and supply connection
  • PR1 : Preset Speed Adjust
  • SW1 : 3Pin Jumper and Closer for Direction change
  • CN1 : DC Motor Supply input 5V to 12V DC





The L293 and L293D devices are quadruple high-current half-H drivers. The L293 is designed to provide bidirectional drive currents of up to 1 A at voltages from 4.5 V to 36 V. The L293D is designed to provide bidirectional drive currents of up to 600-mA at voltages from 4.5 V to 36 V. Both devices are designed to drive inductive loads such as relays, solenoids, DC and bipolar stepping motors, as well as other high-current/high-voltage loads in positive-supply applications.

Each output is a complete totem-pole drive circuit, with a Darlington transistor sink and a pseudo- Darlington source. Drivers are enabled in pairs, with drivers 1 and 2 enabled by 1,2EN and drivers 3 and 4 enabled by 3,4EN.



Pro Audio Microphone Pre-Amplifier Using INA217 and OPA2137

Its simple Tiny Pro-microphone Pre-Amplifier using INA217 instruments amplifier and OPA2137 op-amp. Circuit has been designed using SMD components, 3 Pin female XLR connector has been used for direct micro-phone input.

The board has been design around INA217 low distortion, low noise instrumentation amplifier. The INA217 is ideal for low-level audio signals such as balanced low-impedance microphones. Many industrial, instrumentation, and medical applications also benefit from its low noise and wide bandwidth. Unique distortion cancellation circuitry reduces distortion to extremely low levels, even in high gain. The INA217 provides near-theoretical noise performance for 200Ω source impedance. The INA217 features differential input, low noise, and low distortion that provides superior performance in professional microphone amplifier applications. An OPA2137 op-amp used as a feedback to eliminate the offset voltage. Phantom power is not part of the circuit its just for reference. 


  • Supply Dual +/-15V DC
  • Output Unbalance Single Ended
  • PR1 Gain Adjust G=1+10000/Rg PR1









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