[TriEmbed] Coffee roaster sanity check

[Craig Cook]

 Thanks for the schematic. That helps.

> It's atemperature-controlled switch.



Ah, that makes sense.  I've had my main coffee roaster quit a few times due to overheating (worse during summer).  Have to let the unit sit for 5+mins to cool down before it starts working again.

> Don't try to siphon power from this device to run your Arduino.  You're 
much better off powering it from an isolated supply.
Oh, I was planning to use a good external 5 volt supply for the Arduino.
My first diagram I had removed the 20 volt AC from the unit and used an external 19 volt DC supply to power the fan.  Did that to test PWM from the Arduino to control fan speed. 

The MOSFET in the diagram is being used for PWM fan control. It interrupts the neutral fan wire.

I still plan to use PWM to control fan speed, but I think that is not necessary to use the dedicated DC supply for the fan.

Controlling the heater with PWM would be useful.

Could this technique work? "Bresenham algorithm" with SSR?https://electronics.stackexchange.com/questions/304148/is-there-a-way-to-use-pwm-to-control-ac-mains-powered-heater
A simple on/off with the SSR is also fine to get me started. The instructables code example cuts power when the temperature probe says it is too high. That should be fine. When it is low enough, it turns on again.

>Anyway, I hope my ramblings have been helpful!

Absolutely!
Thanks
Craig
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