Electronic – How to turn on LED with temperature sensor

sensortemperature

I'm new to electronics and I want to control a device using a temperature as an input.

Right now I saw this video on youtube and want to follow it as well as know what the components are for.

https://www.youtube.com/watch?v=PkRJBQgjLrc

From the video I know that the NTC MF52-103 is the temperature sensor and that its output is a resistance. I just don't know how to set/configure the resistance to the temperature I want to control as well as what are the purpose of the two other transistors.

Fan circuit 'diagram'

Best Answer

You could do something like in the schematic below. Let R2 be your NTC. It's probably best if you replace R5 with a potentiometer do be able to adjust your threshold. As long as V+ of the OPAMP is lower than V-, its output is pulled low so the LED will not be lit. With the temperature increasing, the reistance of R2 will drop and V- will sooner or later be lower than V+, so the OPAMP will pull the output high and the LED goes on. This just works well if you have one specific temperature threshold wo which you can calibrate the circuit. Keep in mind that NTCs have non-linear characteristics.

schematic

simulate this circuit – Schematic created using CircuitLab

In a next step you could replace the simple comparator with a so called Schmitt Trigger to prevent the LED from flickering when the temperatur is exactly at your threshold.

Edit: I just saw that the video is a fan controller and not a temperature depending LED, so what exactly do you want? The video explains pretty clear what components are used and how they're assembled.

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