LED lighting thermal fuse

[Buddha_Nature]

I'm building a grow light that has 30 3w LEDs using a driver with the following specs and would like to add a thermal switch or fuse to protect it from overheating. Any ideas of what I should use? I plan to mount them (LEDs) to a heatsink with fans.
100W; Input voltage: AC 100~240V 50/60Hz; Output voltage: DC 8~12V; Output current: 8A

 

[chopnhack]

Watcha growin?

 

[Gryd3]

Parsley, maybe some thyme and wheatgrass? No matter, leave the details out and it makes no difference.
As an aside... Chlorophyll likes to absorb some specific wavelengths more than others.
Simply using white will work to a limited degree, but if you can get your hands on some LEDs in the red, and ultraviolet range, you'll have better luck. There are also 'grow' light specific LEDs that operate in those wavelengths.

Anyway.. there are a couple options for you... you can simply cram a thermal fuse onto the heatsink, or you can put a temperature probe on it and use a comparator to be able to adjust the sensitivity on the fly. (Simply use it to trip a relay and cut power... when the device cools down again you can auto-power it back up. Just make sure to use hysteresis if this is the plan you want to use.)

 

[Buddha_Nature]

Not knowing how hot this is going to run, the comparator/probe idea is probably the best option. I didn't want to add a 12vdc circuit as I was trying to keep this project as simple as possible, but safety first!
I'm growing tomatos
I'm running red 660nm + 625nm and blue 460nm + 445nm which should cover the the desired spectrum.

 

[FORMER AVIONICS TYPE USN]

What manner of overheating? The LEDs themselves? If so and you do want it as simple as possible a "klixon" type bimetallic thermostatic switch would work. Available in just about any cut-out/cut-in range. "Hysteresis" built in, and can be self resetting or manual reset.
And did I mention cheap? For greatly improved reliability use two in series.
I will look for a good source and report back.

So what is the maximum allowable temperature that you wish to limit your LED/heatsink assembly to?