# I want to make a circuit that can sense 37° or more than temperature

#### reha

Joined Jul 20, 2020
8
I want to make a circuit that can sense 37° or more than temperature. Can anybody help me?

#### dl324

Joined Mar 30, 2015
12,688

#### jpanhalt

Joined Jan 18, 2008
11,088
Welcome to AAC.

Do you want digital or analog?

If the temperature is >=37°C, do you want it to do something?
How accurate does it need to be?

Adafruit (adafruit.com) and SparkFun (sparkfun.com) both have temperature sensors that will do that.

#### MrChips

Joined Oct 2, 2009
23,102
There is a circuit called LM35 that gives a linear voltage output with temperature, 10mV/°C over a range of -55°C to +150°C

#### reha

Joined Jul 20, 2020
8
Welcome to AAC.

Do you want digital or analog?

If the temperature is >=37°C, do you want it to do something?
How accurate does it need to be?

Adafruit (adafruit.com) and SparkFun (sparkfun.com) both have temperature sensors that will do that.
I want ana
There is a circuit called LM35 that gives a linear voltage output with temperature, 10mV/°C over a range of -55°C to +150°C
But I want a circuit that will work only after the temperature is less than equal to 37° . Want accurate result. Is there any solution?

#### reha

Joined Jul 20, 2020
8
Welcome to AAC.

Do you want digital or analog?

If the temperature is >=37°C, do you want it to do something?
How accurate does it need to be?

Adafruit (adafruit.com) and SparkFun (sparkfun.com) both have temperature sensors that will do that.
I want analog. I want a circuit that will work only after the temperature is less than equal to 37° . Want accurate this much accurate circuit. Is there any solution?

#### jpanhalt

Joined Jan 18, 2008
11,088
Adafruit (and others) sell analog devices. Did you check?

#### Irving

Joined Jan 30, 2016
1,203
Not enough information. measuring temperature is conceptually easy, many solutions.

Given 37degC is ~ human body temp, is this sensing on contact or from a distance. How quickly do you need a reading after contact? eg<1s? how often do you need a reading, every second, or faster or slower? How accurate do you need it?+/-1degC, +/-0.1degC.

What are you measuring temperature of? air, liquid, solid?

#### reha

Joined Jul 20, 2020
8
Not enough information. measuring temperature is conceptually easy, many solutions.

Given 37degC is ~ human body temp, is this sensing on contact or from a distance. How quickly do you need a reading after contact? eg<1s? how often do you need a reading, every second, or faster or slower? How accurate do you need it?+/-1degC, +/-0.1degC.

What are you measuring temperature of? air, liquid, solid?
I need a circuit that will glow (led) only if the temperature cross 37°.

#### Irving

Joined Jan 30, 2016
1,203
Yes, but temperature of what? how fast is temperature changing? How close to 37degC, within 1deg?

#### reha

Joined Jul 20, 2020
8
Temperature of air. The temperature will remain same. If it cross then the led will glow. It will glow even if the temperature will reach to 37.5°. or can it be more accurate. It should response if the temperature will reach 37.1° c.

#### Irving

Joined Jan 30, 2016
1,203
Is this still air in a box, or moving air in a room? How quickly does air temperature change...

Try to give a complete picture of what you want and why you want it. Its hard work finding out in little bits like this.

#### reha

Joined Jul 20, 2020
8
The air will be in a box . It wil not move or blow

#### Irving

Joined Jan 30, 2016
1,203
Then a simple sensor will probably do what you want. What do you want to power the LED from?

#### jpanhalt

Joined Jan 18, 2008
11,088
It sounds like you are making an incubator of sorts. Incubators for microorganisms almost always have fans to circulate the air gently so a constant temperature is maintained throughout.

#### Irving

Joined Jan 30, 2016
1,203
Yeah, I was thinking the same. but its like trying to swim through treacle this....

#### reha

Joined Jul 20, 2020
8
It will be project for Covid-19. If Human released breath temperature cross 37° that mean he/she has fever. And exactly at that moment the sensor will sense and will glow led to notify danger alert

#### jpanhalt

Joined Jan 18, 2008
11,088
Isn't it easier and more sanitary to measure forehead temperature?

#### reha

Joined Jul 20, 2020
8
No it will be contactless. As the human released breath is pretty equal to the body temperature so I decided to make a heat sensor.

#### jpanhalt

Joined Jan 18, 2008
11,088
It is often thought that our body temperature is 37°C and that is everywhere in or on our bodies. That is not the case.

The value of 37°C is core body temperature. It varies from human to human (See:Wikipedia), location where it is measured, and by sex: