what are suitable Arduino temperature sensors??

m looking to create a temperature sensor that triggers an alarm when a heat source directly touches the temperature sensor, e.g a hot water spillage, what type of sensor would be suitable for this purpose??
Please help as it's for a school project and i'm very new to this :)))
thankyou for any help you can offer :slight_smile:

a thermistor would work.

That Kind of depends on the rest of the design in your Project. A DHt11 or DHT22 DS18B20 are simple to use and only require one analog pin. However, they give values between 0 and 1023 only and are not exactly accurate. If your Project already has I2C implemented or you can include it, I prefer a MCP9808. There are lots of sensors and each have their place. You have to decide what your requirements are.

The above is misleading. A DS18B20 is not an analogue device and can go on any available pin.. It also gives you up to 12bit resolution and in plain English. Having said that, a thermistor should suffice, as it would seem that all you need is an indication of a substantial change from ambient.

the above is misleading. a A DS18B20 sensor is an analog device and must go on an analog pin.

a A DS18B20 MODULE can be SPI or I2C, and produces an output between 0 & 1023

  1. There are 3 posts above your post -- which one is misleading?

  2. What is the traditional (accepted/defined) definition of an analog sensor/device?

  3. What is this device with this registration/type number: DS18B20?

  4. What is the traditional (accepted/defined) definition of a Module? For example:
    (1) This is DS3231 Device/Chip
    ds3231chip.png

(2) This is DS3231 Module
ds3231Pic.png

ds3231chip.png

ds3231Pic.png

GolamMostafa:

  1. There are 3 posts above your post – which one is misleading?

Don’t bother labouring with this nonsense. You will never get the message across to such a complete idiot, who either has not, will not, or cannot, read the first line of the DS18B20 data sheet. I only hope the OP has the good sense to do so - when he/she needs to.

teganko:
m looking to create a temperature sensor that triggers an alarm when a heat source directly touches the temperature sensor, e.g a hot water spillage, what type of sensor would be suitable for this purpose??
Please help as it's for a school project and i'm very new to this :)))
thankyou for any help you can offer :slight_smile:

what are your skills ?
when you say to detect water spillage, I take that to mean able to be submerged
you can find thermistors that are in a small can with some wires to make it waterproof.
thermistors are super easy to use.


the incorrect statement was "the DS18B20 is analog"
the DS18B20 is digital, but uses 1 wire.
easy to use and comes in a water proof version

If I were to select as temperature sensor for water, it would be the Thermistor or the DS18B20

assuming you want to know if the temperature jumped more than 5 degrees in a few seconds, both are excellent.
the reason there are so many choices is because there are so many applications.
the better the details of what you need, the easier it is to select ones that will meed your needs

people like you are why this board needs an ignore list
DALLAS 18B20 DS18B20 TO-92 Wire Digital Thermometer Temperature IC Sensor

DS18B20-3-pins-wire-digital-thermometer-temperature-IC-sensor-module

wireless version

  1. There are 3 posts above your post -- which one is misleading?

the one written by the child

there are wifi, RTC, both DS3231 % DS1307 versions, raw sensors, sensors in modules..

and this board needs an ignore list

I agree.

Going back to the original poster, for the original requirement I think I would choose a thermistor. They are cheap and reliable. You could, if you wanted, set up an analog circuit to trigger the comparator interrupt when a pre-set temperature occurs.

http://www.fiz-ix.com/2012/01/introduction-to-arduino-interrupts-and-the-atmega328-analog-comparator/

On the down side, you'll need to do some calibration to get much actual accuracy, if you need to actually measure an accurate temperature value for some reason.

http://www.circuitbasics.com/arduino-thermistor-temperature-sensor-tutorial/

So... which one is correct? Is a DS18B20 a digital or analog sensor in your opinion? You contradict yourself.

And +1 for a thermistor, sounds like a good solution for this project. Cheap and near indestructible.

sigh.....

teganko :
the consensus on this thread is that the thermistor is the easy one to use.
you need to calibrate it, but that is rather simple.
the water around the ice in a glass is close enough to 0 to use as 0 [ edit 0 C or 32 F thanks wvmarle]
water boiling, a rolling boil, is 212 degrees. so you can calibrate it in your kitchen with nothing more than some ice, some water and a stove.
the DS18B20 requires a library, a lot more code, but as a digital device the values can come in with the temperatures without any calibration.
http://arduinoinfo.mywikis.net/wiki/Brick-Temperature-DS18B20
temperatures from my bench , 5 minutes apart.

67.8
67.2
67.1
67
67.2

and the graph. it shuts off with the grow lights on the seedlings graph

dave-in-nj:
the water around the ice in a glass is close enough to 0 to use as 0
water boiling, a rolling boil, is 212 degrees. so you can calibrate it in your kitchen with nothing more than some ice, some water and a stove.

Ice water is 0°C (32°F).

Boiling water is 212°F (100°C).

Choose one :slight_smile:

wvmarle:
Ice water is 0°C (32°F).

Boiling water is 212°F (100°C).

At sea-level…

Boiling. At sea level, water boils at 100 °C (212 °F). For every 500-foot (150 m) increase in elevation, water's boiling point is lowered by approximately 0.5 °C. At 8,000 feet (2,400 m) in elevation, water boils at just 92 °C (198 °F).

So, the calibration process of the thermistor would involve:
therx.png
Figure-1: Incorrect/faulty Wiring diagram of thermistor
ther.png
Figure-1: Corrected wiring diagram of thermistor.

1. Place only the thermistor element in the ice water (use temperature proof wires to maintain connections of thermistor with R1-terminal, A5-pin, and 5V); also, place a thermometer in the ice water. Measure voltage at A5-pin using a DVM. Record this measurement as: A(T10C, V1).

2 Boil the water until it starts evaporating. Measure voltage at A5-pin using a DVM. Record this measurement as: B(T20C, V2).

3. The unknown temperature point is: C(T0C, V).

4. Now, find equation of T in terms of V; find relation between V and analogRead(A5);. Let the VREF voltage of the ADC be at DEFAULT (5V).

5. Finally, we will have an equation for T in terms of analogRead(A5);. We can present T in integer/float format.

therx.png

GolamMostafa:

Figure-1: Wiring diagram of the thermistor

This shows A5 connected to the 5V rail. You want your ADC connected to the other side of the thermistor, where the thermister forms one leg of a voltage divider between Vcc and ground and your analogue reading comes out the middle.

GolamMostafa:
So, the calibration process of the thermistor would involve:

I thought it was normal to have an additional resistor to make a divider.

A TMP36 sensor would make the project pretty easy. They are cheap, accurate and easy to use, runs on 3.3 or 5 volts. The range goes from way below zero to sufficiently above boiling. You don't need to calibrate it or anything.

gardner:
This shows A5 connected to the 5V rail. You want your ADC connected to the other side of the thermistor, where the thermister forms one leg of a voltage divider between Vcc and ground and your analogue reading comes out the middle.

Nick_Pyner:
I thought it was normal to have an additional resistor to make a divider.

Thnaks to both @gardner and @Nick_Pyner for pointing out the issue.

While typing, we have typo errors; while making a drawing, we do have errors; unfortunately, there is no saying in favor of that 'this is an error'.

If wished, it can be viewed as this way -- there is an omission (by mistake) the connection of the junction-point of Rth-R1 with A4-pin. Signal of A5-pin (Figure of Post#14) can be used for the real-time adjustment of the VREF value of the ADC.

The corrected diagram is posted below:
ther.png

ther.png

GolamMostafa:
Signal of A5-pin (Figure of Post#14) can be used for the real-time adjustment of the VREF value of the ADC.

Diagram looks correct but that just doesn’t make any sense. If only because you normally want Vref to be equal to Vcc (if doing ratiometric readings like in your case), or as stable as possible (when reading e.g. the TMP36 or other sensors with absolute voltage output).