Temperature Shutdown - Auto duty-cycler (schematics)

[djQUAN]

If you're mathematically inclined, you can use the datasheet and find the temperature constant of the thermistor and set the trip points on your desired temp vs resistance.

If you're like me, (not mathematically inclined ) you can stick the thermistor temporarily to an object of known temperature that you want it to trip like a glass of warm water and adjust the set point at that temperature.

 

[Leodahsan]

The LM35 costs $6 here. 4x more than the whole project, and it outputs 10mV/ºC... AND it don't fit behind the 5.6mm laser diodes...

Anyways a good trip point (IMO) is 55ºC for a LED (or fan) to turn on, and 60ºC for the whole laser going off. Some manufacturers rate their diodes as 50ºC, some as 70ºC...

60ºC is a little too hot to touch, uh? If you just can't maintain your finger for >3 secs on a cup of hot water (good idea using water, QUAN), it is around 60ºC, right?

Anyways, with a 5% tolerance thermistor we can just look at the datasheet.
I've even drawn a graph.