The addition almost makes the circuit a perfect incubator design. Thank you for your responses sir which of the circuit is advisable to be buildthe first diagram or the second diagram thank you. Join us in our noble quest to turning every house into a truly cozy home. I need as an example of a closed loop feedback control system. Without an effective hysteresis the circuit would respond fast making the heater lamp switch at rapid frequencies at the threshold levels. please sir, what will happen if the circuit can not trip but functioning. Is there any special formal for setting resistor preset. Sir Swagatam, did you mean that when I remove the pin 2 along with the positive rail manually, the pin 6 voltage should switch from 12/15v to 0? Besides that, the unique design of these incubators lets you choose basic or advanced thermostat modules. Good day Sir Swagatam, i will be making this projet and i will base on your circuit as a reference =) I only have samome basic concepts questions. 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 comparatorwith 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. Im a little bit confused about that, because when I bought the variable resistors the 200ohms Variable resistor is a little blue and white preset with a number indicated 202, and when I looked at the P1 100k it is the same little blue and white preset but the number indicated is 104, so I was thinking if it was just 100ohms, and not 100k ohms, its confusing because there is no name indicated unlike the pot. With the high accuracy of displaying and controlling readings, this thermostat makes temperature measurement a simple task. The setting up adjustments could be done in the following manner: connect a RED LED in series with R2, and adjust VR1 until this LED begins glowing at the required high temperature from the heater (not to exceed 100 degrees C), ignore the relay response during this setting. Sir please tell me what do you mean by positive level???? However I'm having trouble knowing the use of the Variable Resistors. Thank you Patea, yes you can use LM3914 in place of LM3915. Switching a particular load at different threshold temperature levels doesn’t necessarily need complex configurations to be involved in an electronic circuit.Here we discuss a simple construction procedure of an electronic incubator thermostat. My comment was posted twice, I'm new to blogs, I didn't know that the first one was published. This simple electronic incubator thermostat will very faithfully sense and activate the output relay at different set temperature levels from 0 to 110 degree Celsius. but if the above response is not making pn6 low then the IC is faulty ….I also told to connect an LEd in series with base of the transistor for getting an indication…may be you did not do that as well. thank you for this very useful circuit. 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. The Incukit XL can be customized with one or two heater modules, and with regard to various temperature measurement factors. Hi Sir Swagatam, I've got another problem, since there's no regulator, the voltage at pin 3 goes up to 7 to 7.2 voltage instead of 6 due to the Voltage Divider so I tried making the voltage at pin 2 slightly near below the voltage at pin 3 at around 6.8 volts hoping for the op amp output to be low and for the relay to operate. It also features a unique countdown hatch timer and provides the option to regulate an egg turner motor. The voltage at pin 2 increases but the moment that the voltage at pin 2 goes above pin 3, the voltage at pin 1 suddenly goes to 0, but when the voltage at pin 2 goes back below the voltage at pin 3 the voltage at pin 1 goes back also to 13V the others voltages remains the same, The Pin 6 should be the one doing this not the pin 1. these are the only computations available. Connect an LED in series with R2 to indicate the temperature change. Actually, I have a little request to make and I hope this does not burden you that much. Thanks swagatam for your valuable comments also i am need your help please help me on this. Thank you very much for such wonderful contributions in this world. Hi Christian, replace R4 with a 6V zener diode, that will take care of the unstable reference at pin3. Now bring a 38 degree heat source very near to the LM35, and slowly adjust the preset until the relay just switches ON. The unique design of the thermostat is preset to 99 degrees to make it convenient. what diagram is better one the first or second? sir I want to find out must the whole unitbe inside the incubator box or only the bc547 should be in the box?thank you. Thank you again sir! I had a question about the incubator using IC LM35 on post. you are unnecessarily making a simple concept too complex. It also has a unique design that makes it take and record temperature readings for your unique needs. Users will also appreciate that the thermostat can support Fahrenheit mode, and is also simple to set. I don't think that the Relay was even turned on because when I tried to put the BC547 near the heat source, still nothing has changed, It doesn't turn off. With the Inkbird ONLY heating thermostat, you can easily make temperature measurement a simple task. i'm waiting for your suggestion…. Sir Swagatam, Thank You so much for your continuous help, I wrote the details of the point where the relay clicks when the sensor is being heated inside the incubator, but I'm curious at some point, for example if the sensor is heated and the relay clicks at 7v so the moment that the voltage at pin2 increases up to 7V the heat source will turn off, and it slowly cools the sensor which makes the voltage at pin 2 dropping, so the moment that it drops the voltage below 7volts the heat source will again turn on, This will make the desired temperature disturbed, is there a way that the heat source will just turn on again when the voltage at pin2 reaches the initial point? I have been researching on analog thermostat for my homemade incubator. Besides that, this wafer thermostat for incubator also features a unique dual display window that is able to display both the temperature and time set. for second diagram P1 = 1k, BC547 is the only sensor near heat source.keep P2 at center, set VR1 roughly to activate the relay at about 70 degree temp, after this only P2 may be used for getting other desired thresholds. Hello Sir Swagatam , i have some doubts in this design for my project 1. i want to control the temperature cutoff at 75 celsius and on the voltage at 45 degree celsius . 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. i really want to build your circuit but 400 ohms relay is not available..can i use 320 ohms instead? ill try to do that.. but my multitester is defective so i cant get accurate reading specially for ohms..for now i cant afford to buy a digital one..maybe sir ill try to look for presets at stores and use different names like trimmer or trimpot.. im not sure sir if their just the same. It basically depends on Ub (supply voltage), R1 and R2. will depend on the size of the heat source. The thermostat also comes with a unique sensor relay for super-accurate results. thank you sir for your help……can I make this circuit cut of at 38C and start at 36C (I want sensitive thermostat, yes you can set it at any desired point within 100 degree range, the inclusion of the opamp makes sure that the cut-off is sharp and accurate, sir which is better bc547 or 2n3904 or 2n3906 to use as a sensor ??? Each heather and fan module provides an exceptional 125 watts of power. so the moment pin2 voltage goes above pin3, the relay is supposed to switch ON (pin6 should go low)….you just need to confirm this now…. Equipped with a countdown hatch timer, this unit provides users with the option to regulate an egg turner motor. I can read diagrams and some components but not very much. But just to be sure, i want to thank you again and i appreciate it very much for replying to my questions!I cannot find any way to private message you so i will put my request here to you.. Using wood glue and 1-inch nails, create a five-sided cube, leaving the top open. I am also the founder of the website: https://www.homemade-circuits.com/, where I love sharing my innovative circuit ideas and tutorials. Test the incubator. I have tried the second circuit(without opto LED/LDR compo),on that am used a 24vdc as input to the Ic 7812 circuit used 12v and my load is 24v dc. Let's learn more. Also, the thermostat can control the temperature by setting the temperature set and difference value. Your email address will not be published. Is it missing from the second schematic or not necessary?Thanks,Dan. Degrees Celsius connects with the Inkbird only heating thermostat, you can use this site we assume. Begins illuminating the relay not to overheat BC547 controlled fan a 200 ohms preset as the heat source does turn. Through-Out the incubation say that your blog is very informative aside from the incubator. 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