Aug 27, 2016

Making a Thermoelectric Generator Circuit (TEG)

A thermoelectric generator (TEG) is a kind of "free energy device" which has the property of converting temperature into electricity. In this post we learn a little about this concept and find out how we can use it to generate electricity from heat and cold.

In one of my earlier articles I have already explained a similar concept regarding how to make a small refrigerator using a Peltier device

A Peltier device is also basically a TEG designed for generating electricity from a difference of temperature.

A thermoelectric device is quite similar to a thermocouple, the only difference being in the composition of the two counterparts. In a TEG two different semiconductor materials (p-n) are used for the effect whereas a thermocouple works with two dissimilar metals for the same, although a thermocouple might require a substantially larger difference of temperature compared to the smaller TEG version.

Also popularly known as the "Seebeck" effect, it enables a TEG device to initialize the generation of electricity when subjected to a difference of temperature across its flip sides.

This happens due to the specially configured internal structure of the device which utilizes a couple of doped p and n semiconductors for the process.

According to the Seebeck principle when the two semiconductor materials are subjected to two extreme temperature levels, initiates an electron movement across the p-n junction resulting in the development of a potential difference across the outer terminals of the materials.

Although the concept appears to be amazing, all good things come with an inherent drawback and in this effect too their is one which makes it relatively inefficient.

The need of extreme difference in temperatures across its two sides becomes the most difficult part of the system, because heating up one of the sides also implies that the other side would also heat up which would eventually result in zero electricity and a damaged TEG device.

In order to ensure an optimal response and for initiating the flow of electrons, one semiconductor material inside the TEG needs to be hot and simultaneously the other semiconductor needs to be kept aloof from this heat by ensuring a proper cooling from the counter side. This criticality makes the concept a little clumsy and inefficient.

Nevertheless, the TEG concept is something which is exclusive and not feasible using any other system so far, and this uniqueness of this concept makes it much interesting and worth experimenting with.

I have tried to design a TEG circuit using ordinary diodes, although I am unsure whether it will work or not, I am hoping some positive results could be achieved from this set up and it has a scope for improvement.

Referring to the figures we can witness a simple diode assembly clamped with heasinks. The diodes are 6A4 type diodes, I have selected these bigger diodes in order to acquire larger surface area and better conduction rate.

Diode 6A4

The simple thermoelectric generator circuit set up shown above could be possibly used for generating electricity from waste heat, by suitably applying the required degrees of heat difference across the indicated heat conducting plates.

The right side figure shows many diodes connected in series parallel connections for achieving higher efficiency and proportionately higher accumulation of potential difference at the output.

Why Use a Diode for Making a TEG

I have assumed that diodes would work for this application since diodes are the fundamental semiconductors units consisting of a doped p-n material embedded within their two terminating leads.

This also implies that the two ends are specifically composed of the diverse materials facilitating easier application of temperature separately from the two opposite ends.

 Many such modules could be built and connected in series parallel combinations for achieving higher conversion rates, and this application could be implemented using solar heat also.

The side which needs to be cooled could be achieved through air cooling or through an enhanced evaporative air cooling from atmosphere for increasing the efficiency rate.

Aug 25, 2016

Deep Soil Metal Detector Circuit - Ground Scanner

The post discusses a simple deep under soil metal detector circuit for evaluating hidden metals such as gold, iron, tin, brass etc by detecting change in the resistance of the relevant soil layers.

Bigger physical objects which might be buried within the topsoil could be unveiled through a modification in the electrical resistance of the soil layer at various depths. The design is about a device which may be for implementing relative enhancements on the resistance of the soil. This particular application can be particularly handy in archaeological excavations.

Deep Soil Metal Detector Circuit - Ground Scanner

The proposed deep soil metal detector instrument includes the measuring bridge (figure 1), the alternating voltage generator (fig 2) and the a couple of probes, sunken inside the soil.

The resistances across the soil layers, between the electrodes of probes are coupled to the input of the bridge arms, for measuring the parameters.

Prior to measurement through 100 ohm resistor may be adjusted for bridging the balance so that the dial instrument readings are initially at the minimal.

The design of the probe represented in FIG.3 may e understood as follows:

Each of the probes signifies the insulated rods having a diameter of around 1.5 mm. on the surface area of the bar along its axle, these are fixed electrodes in the form of six thin-walled tube, separated from each other.

Each electrode probe with the aid of six cable connection is attached to the switch S1 measuring bridge, that in turn hooks up with one of the six pairs of electrodes together with the bridge.

In this instance, each pair of electrodes at each of the positions of the switch S1 corresponds to the precise depth of the soil layer.

Soon after placing the probe on earth, in accordance with FIG. 4, the electrical resistance of the subsequent layers of soil located different depth is detected.

Evaluating the values acquired from the resistance, you are able to draw a conclusion at what depth (which soil layer) are objects that might be changing the resistance of the soil.

The space between the probes are pretty much decided on in each specific scenario. Occasionally, great outcomes could be obtained with distance that me approximately close to 2.4 m.

The variable resistor of the bridge is 500 ohms as shown in the deep soil metal detector circuit diagram, is for controlling the sensitivity of the bridge depending on soil type being investigated.

Courtesy: The Radio-Constructor, 1966, 8

Aug 24, 2016

IR Remote Control Circuit Using Arduino

In this post we are going to construct a customizable IR (infrared) based wireless remote control switch, which consists of IR remote and a receiver, you may modify according to your needs.

By: Girish Radhakrishnan

If you are above beginner level you can accomplish it with ease. The proposed circuit illustrated here just has three controls on remote and 3 relays on receiver end. You may modify the code and circuit diagram to fulfill your needs.

You’ll need two Arduino boards, which act as remote and another act as receiver. I would recommend Arduino pro mini for this project, since the sizes of them are pretty small and the overall size of the remote could be shirked.

You may use 3.3V based Arduino pro mini for remote so, that you can be powered with two button cell or two AA size batteries, according to your needs.

The IR transmitter circuit has 3 push to on buttons and an IR LED for sending commands to receiver. Each button has programmed with unique hexadecimal code, the same hexadecimal code is programmed on receiver side too.

When a button is depressed the IR LED sends out the hexadecimal code to receiver, the receiver will recognize which of the button is pressed and it switches the corresponding relay ON/OFF.

The proposed remote uses RC5 protocol for communicating with receiver; you may change everything by modifying the code.

If you are just beginner in Arduino, you can still accomplish it just follow the diagram and upload the code without modifying.

The circuit and program:

Arduino Remote Transmitter:


The above circuit illustrates how to build the Arduino IR remote transmitter.

The three 10K resistors are pull down resistors, which prevent accidental triggering of the remote due to static charge and a 220ohm current limiting resistor is employed for IR LED.

Program for Remote Transmitter:

//---------Program developed by R.Girish--------//

#include <IRremote.h>
IRsend irsend;
const int button1 = 4;
const int button2 = 5;
const int button3 = 6;
void setup() {
  pinMode(button1, INPUT);
  pinMode(button2, INPUT);
  pinMode(button3, INPUT);
void loop()
  if (digitalRead(button1) == HIGH)
  irsend.sendRC5(0x80C, 32);
  if (digitalRead(button2) == HIGH)
  irsend.sendRC5(0x821, 32);
  if (digitalRead(button3) == HIGH)
  irsend.sendRC5(0x820, 32);
 //---------Program developed by R.Girish--------//

Arduino Receiver:

The IR Arduino receiver  circuit as shown above consists of TSOP1738 sensor few transistors, current limiting resistors for transistor, relays and diodes for absorbing high voltage spike from relay coils.

The circuit diagram is self explanatory.

Program for Arduino receiver:

//-----------------Program developed by R.Girish-----------//
int input = 11;
int op1 = 8;
int op2 = 9;
int op3 = 10;
int intitial1;
int intitial2;
int intitial3;
IRrecv irrecv(input);
decode_results dec;
#define output1  0x80C    // code received from button A
#define output2  0x821   // code received from button B
#define output3  0x820  // code received from button C
void setup()
void loop() {
  if (irrecv.decode(&dec)) {
    unsigned int value = dec.value;
    switch(value) {
       case output1:
         if(intitial1 == 1) {       
            digitalWrite(op1, LOW);
            intitial1 = 0;          
         } else {                     
             digitalWrite(op1, HIGH);
             intitial1 = 1;         
       case output2:
         if(intitial2 == 1) {
            digitalWrite(op2, LOW);
            intitial2 = 0;
         } else {
             digitalWrite(op2, HIGH);
             intitial2 = 1;
       case output3:
         if(intitial3 == 1) {
            digitalWrite(op3, LOW);
            intitial3 = 0;
         } else {
             digitalWrite(op3, HIGH);
             intitial3 = 1;
//--------------Program developed by R.Girish-----------//

By following the above explanations you can accomplish three controls, if you want to add more controls and relay, you need to edit the code and circuit diagram.

You can assign output and input for unused pins in the receiver and remote in the program and connect number of transistor and relay for the respective pins in receiver and similarly connect number of switches and pull down resistor in remote.

You can use random hexadecimal code for assigning more number of buttons.

For example: 0xA235, 0xFFFF, 0xBA556 and so on. And also add the same hexadecimal value in receiver code too. For example: #define output4 0xA235, #define outout5 0xFFFF and so on.   

Aug 23, 2016

Natural Mosquito Repellent Circuit Using High Watt Resistor

As the name suggests, to build this simple natural mosquito repellent circuit you will just require a high watt resistor, a few drops of lemon eucalyptus oil and  mains supply input.

You might be already familiar with these popular ready made mosquito repellent units which come in the form of coils, liquids, mats etc, and most of us already use these products for keeping mosquitoes at bay.

Although these methods are effective and help our homes to get rid of dangerous mosquito transmitted diseases like dengue, malaria, hay fever, etc, the chemicals ( mainly DEET) used in these repellents in turn have the potentials to cause many unknown body ailments, which could include lung diseases, severe headache such as migraine etc.
Therefore using these ready made chemical based repellents may not be after all safe either.

An alternative and much safer way of driving away mosquitoes could be by using naturally available options, one of which is available by the name Lemon Eucalyptus Oil.

Lemon eucalyptus oil is extracted from the tree lemon eucalyptus and can be easily procured from any nearby chemist shop or may be ordered online.

Normally this oil is required to be applied on the exposed areas of the body in order to protect from mosquito bites, however it may be much cleaner and safe if its fragrance could be dispensed through in the air instead of applying on body. This could be probably done using a homemade fragrance dispenser circuit

To build the above suggested homemade mosquito liquid dispenser circuit, you would just need a high watt resistor, and a mains input supply.

The set up can be seen in the following diagram:

In the shown set up we can see a high watt resistor and an aluminum dish glues over the resistor.

The resistor leads are terminated into a mains 220V or 120V socket.

The aluminum dish is used for placing a piece of cotton wad drenched with lemon eucalyptus oil.

That's all, once this set up is built and plugged in, the high watt resistor could be seen heating up and enabling the aluminum dish to also heat up, causing the heat to evaporate the oil and its fragrance in the air.

This special fragrance which may not be harmful to humans but irritating for the mosquitoes would ultimately help to drive away the creatures away from our homes, naturally and without any health risks.



Aug 22, 2016

Incubator Temperature Controller Circuit using LM35 IC

A very simple egg incubator temperature controller thermostat circuit using LM 35 IC is explained in this article. Let's learn more.

An Incubator is a system where bird/reptile eggs are hatched through artificial methods by creating a temperature controlled environment. Here the temperature is precisely optimized to match the natural incubating temperature level of eggs, which becomes the most crucial part of the whole system.

The advantage of artificial incubation is faster and healthier production of the chicks compared to the natural process

Anybody involved in this profession will understand the importance of a temperature controller circuit which should be not only reasonably priced but also have features like precise temperature control and manually adjustable ranges, otherwise the incubation could get hugely affected, destroying most the eggs or developing premature offspring.

I have already discussed an easy to build incubator thermostat circuit in one of my earlier posts, here we'll learn a couple of incubator systems having easier and much more user friendly setting up procedures.

The first design shown below uses an opamp and a LM35 IC based thermostat circuit and indeed this looks quite interesting due to its very simple configuration:

 The idea presented above looks self explanatory, wherein the IC 741 is configured as a comparator
with its inverting pin#2 input pin is rigged with an adjustable reference potentiometer while the other non-inverting pin#3 is attached with output of temperature sensor IC LM35

The reference pot is used to set the temperature threshold at which the opamp output is supposed to go high. It implies that as soon as the temperature around the LM35 goes higher than the desired threshold level, its output voltage becomes high enough to cause pin#3 of the opamp to go over the voltage at pin#2 as set by the pot. This in turn causes the output of the opamp to go high. The outcome is indicated by the lower RED LED which now illuminates while the green LED shuts off.

Now this outcome can be easily integrated with a transistor relay driver stage for switching the heat source ON/OFF in response to the above triggers for regulating the incubator temperature.

A standard relay driver can be seen below, wherein the base of the transistor may be connected with pin#6 of the opamp 741 for the required incubator temperature control.

Incubator Temperature Controller Thermostat with LED Indicator

In the next design we see another cool incubator temperature controller thermostat circuit using an LED driver IC LM3915

In this design the IC LM3915 is configured as a temperature indicator through 10 sequential LEDs and also the same pinouts are used for initiating the ON/OFF switching of the incubator heater device for the intended incubator temperature control.

Here R2 is installed in the form of a pot and it constitutes the threshold level adjustment control knob and is used for setting up the temperature switching operations as per the desired specifications.

The temperature sensor IC LM35 can seen attached to the input pin#5 of the IC LM3915. With rise in temperature around the IC LM35 the LEDs begin sequencing from pin#1 towards pin#10.

Let's assume, at room temperature the LED#1 illuminates and at the higher cut-off temperature the LED#15 illuminates as the sequence progresses.

It implies that pin#15 may be considered the threshold pinout after which the temperature could be unsafe for the incubation.

The relay cut-off integration is implemented according to the above consideration and we can see that the base of the transistor is able to get its biasing feed only upto pin#15.

Therefore as long as the IC sequence is within pin#15, the relay remains triggered and the heater device is held switched ON, however as soon as the sequence crosses over pin#15 and lands on pin#14, pin#13 etc. the transistor biasing feed is cut off and the relay is reverted towards the N/C position, subsequently switching OFF the heater..... until temperature normalizes and the sequence restores back below the pin#15 pinout.

The above sequential up/down drift keeps on repeating in accordance with the surrounding temperature and the heater element is switched ON/OFF maintaining almost a constant incubator temperature as per the given specifications.
Swagatam Majumdar
Swagatam MajumdarHi Friends, Welcome to my site, a place where you will discover a massive collection of electronic circuit ideas, mostly requested by the dedicated readers and exclusively designed by me for their customized application needs. I have posted more than 1100 circuit designs in this site, if you have a personalized circuit requirement you may feel free to request it through the comment box, if it seems feasible to me then surely you may find it published here with your credentials attached in the post, thanks and please keep reading

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