high temperature rugged MCUs? (250º)

[Javier1]

Anyone has experience with this, does ST have anything that works beyond 105ºC?

I saw cheap non Flash based 8bit mcus (Z86C04/C08) that go up to 125º-150º

Also (TK68HC811E2) up to 175ºC

I also found an article recommending chips worth 800€/piece

555 chips for 1150€/ 5 pieces...

I want to build an enclosed small ball with an mcu inside to measure the temperature inside cooking pots and ovens. (and somehow wirelessly Tx temperature info back)

[Tesla DeLorean]

Perhaps the approach is not to use an MCU, but rather a simpler radio circuit that has a temperature to frequency/modulation relationship, and powered by a thermocouple.

[Javier1]

Im taking a look at high temp oscillators, (reading back temperature based on the deviation from room temperature oscillation)

powering things by thermocouple... phew ill look into that

dont i need a temperature difference for that to work?

[TDK]

250 C is above the melting point for even lead-free solder, so this will require some interesting assembly techniques.

[Tesla DeLorean · Accepted solution]

>>dont i need a temperature difference for that to work?

I don't know, it's not my area of expertise, I just know that my furnace has a probe in the flame which keeps a value open.

Perhaps some piezo material held across an expanding fork?

More generally my thought would be there has to be a way to harvest energy from the immediate environment, and not try and get to exotic with the hardware.

As you've observed exotic MCU and electronics, perhaps space rated, tends to be very niche and expensive. So the problem needs to be approached from a different angle using the characteristics and properties of things more cheaply/readily available that can work at higher temperatures. Whether that uses radio, or high frequency sound.

Welded rather than soldered.

[TDK]

You do need a temp difference for the thermocouple effect to work. And even if you have that, the power available to draw is incredibly small. Even then, if you have a lower temp available, just put the micro there and run a wire to what you’re measuring.

[waclawek.jan]

Tekmos (you've linked to their "commercial" HT mcu above) has some papers/FAQ, they are worth reading.

Temperature accelerates processes which are generally detrimental for semiconductors, exponentially. There's way more know-how in going from 150C to 175C, than going from 0 to 150C.

JW