[TriEmbed] Coffee roaster sanity check

[Craig Cook]

>I was actually talking about the voltage rating of the optoisolator used to drive the FET gate. The image below more fully describes what I meant. I expect your final circuit for the fan would include most of the items shown below (I am not sure that you would need D2). 

Ah, I was working off this tutorial.
https://itp.nyu.edu/physcomp/labs/motors-and-transistors/using-a-transistor-to-control-high-current-loads-with-an-arduino/
Their example uses a 12V motor. Mine is ~20V. I thought I was "close enough" to make it work.
You are suggesting I need more components, i.e. at least add an optoisolator into the mix.

> How many popcornmakers have you been through on this project? :-) 

LOL. Two have died from natural causes. I fried the heater on the third by running without a fan.

> the heater mightjust be overheating a little bit eachtime, gradually weakening itself until it breaks.  
Yes, that sounds like a great theory as well. The wire on the coil breaks, close to where the windings start. It may be due to the number of heat and cool cycles it goes though.

>Also bear in mind thatyour $30-or-so popcorn popper simply isn't built for longevity. 

Yes. It's supposed to last 12 months of popcorn usage. For most units it's probably rare to be used many times in a 12 month period.
The system I design needs to be reasonably easy to swap out the failed parts, which so far seems to be the heating element.
Thanks
Craig
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