Forget PID... go Arduino - Page 4

October 13th, 2012, 2:19 am

i used an Arduino for both roasting and data logging with real-time graphing as I roast...and the same thing could be put into the caravel for a PID algorithm.

I've since lost the code as I got rid of my caravel and haven't been roasting anymore. But you can do pretty much anything with the Arduino. It's a microcontroller with some inputs and outputs. You just need to add a LCD and a couple a push buttons and a debounce algorithm to use the buttons.

#32: Post by **pcrussell50** » October 14th, 2012, 2:56 pm

allon wrote:Might be that a zero crossing SSR will help, or put a ferrite bead on the SSR control lines. My thinking is that when switching the AC on, it's a crapshoot where in the 60hz cycle it is. As the voltage is switched on, you get an approximation of a square wave edge; this rapid rise (or fall) will induce high frequency harmonics on the line that may couple to the control lines and back into the CPU board. Towards the high ends of the swing the amplitude is greatest; closer to the zero crossing there will be a lower amplitude spike.

A zero crossing SSR waits for the next zero crossing before turning on or off to prevent harmonic spikes.

I've never actually deployed an open source microcontroller in a system of my own design, but is there any reason the logic circuitry can't be a well-conditioned and isolated Vref, leaving the actuation duties to the "dirty" and cruder wall-outlet power? That's how it's done in the hostile underhood region of modern cars where there's all kinds of energetic RF and heat and vibration and moisture and... And if not, wouldn't that solve the problems we are talking about here?

-Peter

#33: Post by **allon** » October 14th, 2012, 5:55 pm

The interference may not be on the Vref lines; also, since it is likely coupled into the wires via RF, the solution is further RF isolation, using ferrites to block rf energy, or some other low pass filter. How is the microcontroller powered?