[TriEmbed] Coffee roaster sanity check

[Pete Soper]

Hi Craig,

    Very few people on this list are going to have KiCad at their 
fingertips, so I transmogrified your schematic into a PDF. Folks may 
have to turn their heads sideways to look at it depending on their PDF 
viewer:

http://triembed.org/doc/craig-cook-coffee-roaster.pdf

   In my opinion the stuff on the left side of the schematic should be 
inside an all metal box with the box connected to earth ground by a good 
power cord with standard three prong AC plug properly wired. You don't 
specify R1 (heater), so it isn't possible to judge whether the current 
capacity of the SSR is up to the task. Two amps seems marginal for a 
heater designed to heat more than a few beans at a time.

   R4 is too large, in my opinion, and the FET turn on time might be 
very slow, but that may be a non-issue. It would be harmless are more 
likely to work well if it was 100 instead of 10k ohms. D1 should be 
swapped end for end  and have 20V on the cathode end, not ground, to act 
as a snubber (i.e. it's in parallel with the motor but only conducts in 
the opposite direction). The 20V of course has to match the voltage 
rating of the actual motor.

   I'm not in the position to judge the display connections. I'm also 
not up on KiCad enough to judge whether you've got the Arduino's five 
volts shorted to ground with the "PWR_FLAG" net, but it seems that way. 
The thermistor circuit seems reasonable.

-Pete

On 12/29/19 10:36 AM, Craig Cook via TriEmbed wrote:
> Would someone be willing to review my kicad drawing of a popcorn 
> coffee roaster?
>
> https://drive.google.com/open?id=141Y2Q9tdyt8iiL_LouNO4CarcEIShBtb
>
> I have the Arduino Uno working. Tested the thermistor, display and fan 
> control. Have not tried connecting the solid state relay yet.
>
> I am basing my work from this instructable: 
> https://www.instructables.com/id/A-fully-automatic-coffee-bean-roaster-Arduino/
>
> Thanks
>
> Craig
>
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