I have a project where I want to measure the temperature of several (12 for the beginning) heat sinks so that I can monitor the mikrochips below them and take action when they get to hot.
I'm not sure though what kind of Thermometer I should use.
I found the following solutions
DS18B20 (digital and thus I can identify them using the serial)
LM35 (a bit cheaper but analog and needs Multiplexer)
What about Thermistors? Can they be used with Arduino as well?
I think it is ok to have +-1 degree Celsius accuracy thus the analog LM35 is precise enough.
I'm rather new to this and thus need advice what would be the best approach for the project.
//TMP36 Pin Variables
int temperaturePin = 0; //the analog pin the TMP36?s Vout (sense) pin is connected to
//the resolution is 10 mV / degree centigrade
//(500 mV offset) to make negative temperatures an option
/*
getVoltage() – returns the voltage on the analog input defined by
pin
*/
float getVoltage(int pin){
return (analogRead(pin) * .004882814); //converting from a 0 to 1023 digital range
// to 0 to 5 volts (each 1 reading equals ~ 5 millivolts
}
/*
setup() – this function runs once when you turn your Arduino on
We initialize the serial connection with the computer
*/
void setup()
{ Serial.begin(9600); //Start the serial connection with the copmuter
//to view the result open the serial monitor
//last button beneath the file bar (looks like a box with an antenae)
}
void loop() // run over and over again
{
float temperature = getVoltage(temperaturePin); //getting the voltage reading from the temperature sensor
temperature = (temperature - 0.5) * 100;
//converting from 10 mv per degree wit 500 mV offset
//to degrees ((volatge – 500mV) times 100) Serial.println(temperature); //printing the result
delay(1000); //waiting a second
}
For your specific project, the temperature sensor should be attached to the heat sink(s). For this reason I would think it should be in a metal package. Looking at the datasheet, I see that DS18B20 only comes in a plastic package. LM35 is offered in 2 metal packages: TO-46 and TO-220. I would definitely chose LM35.
I would say just attach a ds18b20 to the device, and use maybe epoxy to hold it in place, being that most heat transfer happens from the leads they should be epoxied too
I would say ds18b20 is definetly the easiest route
I don't know how epoxy behaves with temperatures in the range of 60-80 Celsius (as I assume the temp of the heat sink will be).
Also, I don't know how good of a temperature conductor the epoxy is.
It also depends on how exact you want your measurement to be.
In the end, it's a trade-off between exactness and ease-of-use. If this is just a hobby project, go for the easy solution.
How much approximate power is dissipated on these heatsinks?
Unless it's very small, the DS18B20's epoxied (with a good sized blob, clean/abrade the surface first) should be fine.
I would suggest running the leads and the first 1-2 cm of the attached leads in the epoxy too, so the small amount of heat conducted away by the leads would be insignificant.