Thermistor for measuring/controlling temperature

All about thermistors for measuring and controlling temperature, including how to use the thermistor that's in an automobile coolant temperature sensor. I talk about the difference between Positive Temperature Coefficient (PTC) thermistors and Negative Temperature Coefficient (NTC) thermistors. I talk briefly about my experiment to test if cold water boils faster than hot water and then talk about the effect of the thermistor's
changing resistance on the electrical current running through a PC fan, to turn the fan on and off. I go over the electrical circuit for it in detail, incuding the homemade power supply, thermistor, PC fan and wiring.

This video has correct English captions. Click on the CC button at the bottom of the video to see them.

To watch "Does Cold or Hot Water Boil Faster?", see here:

To watch how to power a compact fluorescent light using AA batteries, see "How to Make Joule Thief Light a CFL - Jeanna's Light":

Toe watch "Make Solar Cell Transistor Powered Calculator using 2N3055", see here:

For more about my homemade power supply, see my webpage:

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[RimstarOrg]

This week's video is an electronics one all about using thermistors, what they are and how use them to measure and control temperature. I especially had fun doing the simple circuit where I heat up the thermistor with a hair dryer until that causes the fan to turn on. And then the fan cools off the thermistor, causing the fan to turn off!

[RimstarOrg]

Thanks. Another video's in the works. It's just taking a little longer than usual and I don't want to just rush one out.

[RimstarOrg]

This sensor is for attaching to the cooling system in a particular model of car, so you'd have to make your own mounting system.
To turn on a fan below 100C you can do what I did in the video. But it probably won't turn on at 100C. For that you'd need to add a resistor so that the total resistance adds up to something that would result in the right current for the fan. You also have to consider what temperature the fan should turn off at.
Search google for "pexsupply snap disc" for a better way.

[RimstarOrg]

Thanks. Yes, it's a 3 amp, 240 VAC variac which I bought brand new from a local store many years ago.

[jvzz]

Does anyone know where i can get a temp sensor that turns on fan at 95 degrees no matter wat

[jvzz]

how hot did your sensor get to turn on fan ??

also is there a engine coolent temp sensor that will turn on a fan at a 98 degrees

[RimstarOrg]

According to the graph, cold water won't boil sooner than room temp water. Cold water will have a faster heat transfer rate while it is still cold, but once the cold water reaches room temp, the heat transfer rate will be the rate it should be for room temp water. So once the cold water reaches room temp it will take the same time from then on as room temp water does.

[ThomasBurns]

Thanks for this video! Any pointers on how to read a thermistor's label? Does "8L10 10002" mean it acts like a 10K resistor at room temperature?

[MuhdFitriNazri]

this is actually really helpful for my a level. i could easily understand thermistor in less than 5 minutes.

[RimstarOrg]

I don't think it's a rectangular hyperbola since it looks like when it's near freezing the graph isn't parallel to that axis. I don't know what the fact that it's a curve means. Maybe it's something to do with the molecules or the bonds between them, but looking online I couldn't find any insight. And thanks! Glad you're still enjoying the videos.

[GREENPOWERSCIENCE]

Your videos are getting scary AWESOME!! Added to feed and FB.

[RimstarOrg]

Thanks. I'll have a look in a PC power supply for one too. I'm glad it brought you some fun!

[rybread]

wow, this is a high quality video. I wouldn't think it would be 10 years old.

[defensegeneral]

Does it matter what value of resistance I choose, some are 1k ohm, 2kohm up to 10kohm. So if the resistance values goes up and down, does it matter what value its

[RimstarOrg]

I just opened up with only PC power supply I have (outside of a computer) and it has SCK 054, an NTC thermistor. I don't want leave this power supply intact though in case I ever need it as such. At least I now know where to find them. Thanks!

[RimstarOrg]

Hmmm... Now you've got me wondering what's inside those. I'll have to find one and see. I'm glad you enjoyed the video! Thanks!

[Endisupertramp]

Hey Rimstar, great video.

A very clear and practical demonstration that makesit alot easier to understand the use of thermistors.

Thanks. :)

[RimstarOrg]

No need to do the setup with common resistor. I just connected a 1 kohm, 2 watt resistor to my meter and put the same hair drier on it for 1 minute, twice as long as I did in the video, and the resistance increased by only 8 ohms. Common resistors aren't affected by temp. as much as thermistors.
The VARIAC is a 3 amp, 240VAC one which I bought off-the-shelf. I'd recommend higher amperage for more usefulness. Maybe salvage from old power supplies but usually buy second hand since they're costly.

[Ex-fknr]

how do you set a threshold for example when the thermistor reaches a certain amount of temperature the fan gets turn on....thank you?

[firoxlion]

Interesting, but why did you use a capacitor symbol for the NTC?