What capacitor to use

Using Arduino Project Guidance
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Hello. I have arduino uno connected to ntc 100k. Now I have a question why should i use 10uF and not 100uF capacitor? And is electrolyt capacitor ok?

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  • You might be able to.

  • Electrolytic capacitor, make sure you observe polarity when wiring.

Always show us a good schematic of your proposed circuit.
Show us a good image of your ‘actual’ wiring.
Give links to components.

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Most people use 10 or 100 nF (not uF) from the NTC voltage divider tap to ground. The capacitor is required to make up for the large resistance in the voltage divider.

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4

And presumably another resistor in series? The NTC resistor by-itself will be useless.

And also presumably, the capacitor is being used as a noise filter between the Arduino's analog input and ground.

You have an RC time constant so 10 times the capacitance is 10 times slower for 10 times the "smoothing" of any noise.

(For purposes of calculating the time constant, treat the resistors as-in they are in parallel... They both provide a current-path for charging/discharging the capacitor.)

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Yeah, I thought nF not uF sorry my mistake!

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Arduino-Thermistor-Basic-Set-Up-1024x437
Arduino-Thermistor-Basic-Set-Up-1024x4371024×437 59.2 KB

I have it connected like this and 100nf resistor in paralel with ntc.. I have it in egg incubator and sometimes there is big deviation.

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So should I use smaller capacitor?

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Connect a 10 to 100 nF capacitor from the analog input to ground. The value is not critical.

Breadboards are not reliable, so you should solder connections, especially for use in humid environments. Also check for corrosion on wires and connections.

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Everything is soldered. I just dont know why is it jumping.. reading is every 4 seconds and values are diffrent up to 2°C

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Please post a clear, focused photo of your setup, and the code, using code tags.

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int ThermistorPin = 0;
int Vo;                                      
float R1 = 10000;
float logR2, R2, T;
float c1 = 1.009249522e-03, c2 = 2.378405444e-04, c3 = 2.019202697e-07;

void loop()
{
Vo = analogRead(ThermistorPin);
  R2 = R1 * (1023.0 / (float)Vo - 1.0);
  logR2 = log(R2);
  T = (1.0 / (c1 + c2 * logR2 + c3 * logR2 * logR2 * logR2));
  T = T - 273.15;
  T = T + TemperatureFix;
}

https://www.circuitbasics.com/arduino-thermistor-temperature-sensor-tutorial/
I used code from that website, I can send photo tomorrow,
Temperaturefix is value which I can set using rotary encoder which is +/- in decimal values too

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or maybe should I use other code for better values at lower temperature

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A thermistor seems to be a cheap choice for an incubator.
I wouldn't use one, unless it was glass encapsulated.
But then you still have the problem of calibrating it yourself.
A digital (factory calibrated) temp sensor would be a better choice.
Try the DS18B20.
Leo..

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14

Oh, thanks! Before i used dht 22 so that ntc was better i think!

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I didnt know that factory calibrated sensors even exist

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The DHT22 uses a thermistor as temp sensing element.
Leo..

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