Modified coffee roaster
The thermocouple modules made the idea of controlling a coffee roaster seem easy.
I have a Fresh Roast plus which used a mechanical timer to turn the heat and fan on. Turns out it's necessary to follow a temperature roasting profile to get the best flavors out of the roast.
I used 2 25A SSRs (Carlo Gavazzi), one for the fan and one for the heating element. Original idea was to PWM to control the fan and heat, but the serial nature of the PWM command makes that difficult (open to suggestions).
The TC routine is based on the example from parallax. I skip the CJ compensation (mostly out of laziness) will put it back in at some point.
The rest is just basically a thermostat and some useful info written to an LCD and a button to start the roast. Didn't add a circuit diagram but just pull up resistors for the button and the SSRs.
I have a PID version of the thermal control that uses PWM on the heater control. Does very well at matching the set point but I can't get the beans hot enough later in the roast. Even at 100% duty cycle it just can't stay hot. I think it's because the heater switches off for short time when I'm not in the PWM command. But the thermostat version is doing pretty well so... Has anybody used the TC module w/ a propeller chip?
The next step will be to store many roast profiles in scratch and choose which roasting profile to use on a particular coffee bean.
The coffee has never been better [noparse]:)[/noparse]
-Pete
Update: Attached the PID version of the code that uses PWM
Update: Attached a cleaned up version of the code - added the CJ temperature compensation back in and cleaned up the time tracking/display
and added some comments - I should put the parts in a project box for safety.
Update:2007 July 11 - I have ported the application to the propeller chip - does logging via termina right now... Still a work in progress but will upload if anybody is interested. Much cheaper to use the propeller proto board than a BOE+stamp [noparse]:)[/noparse]
Post Edited (rePete) : 7/12/2007 1:30:41 AM GMT
I have a Fresh Roast plus which used a mechanical timer to turn the heat and fan on. Turns out it's necessary to follow a temperature roasting profile to get the best flavors out of the roast.
I used 2 25A SSRs (Carlo Gavazzi), one for the fan and one for the heating element. Original idea was to PWM to control the fan and heat, but the serial nature of the PWM command makes that difficult (open to suggestions).
The TC routine is based on the example from parallax. I skip the CJ compensation (mostly out of laziness) will put it back in at some point.
The rest is just basically a thermostat and some useful info written to an LCD and a button to start the roast. Didn't add a circuit diagram but just pull up resistors for the button and the SSRs.
I have a PID version of the thermal control that uses PWM on the heater control. Does very well at matching the set point but I can't get the beans hot enough later in the roast. Even at 100% duty cycle it just can't stay hot. I think it's because the heater switches off for short time when I'm not in the PWM command. But the thermostat version is doing pretty well so... Has anybody used the TC module w/ a propeller chip?
The next step will be to store many roast profiles in scratch and choose which roasting profile to use on a particular coffee bean.
The coffee has never been better [noparse]:)[/noparse]
-Pete
Update: Attached the PID version of the code that uses PWM
Update: Attached a cleaned up version of the code - added the CJ temperature compensation back in and cleaned up the time tracking/display
and added some comments - I should put the parts in a project box for safety.
Update:2007 July 11 - I have ported the application to the propeller chip - does logging via termina right now... Still a work in progress but will upload if anybody is interested. Much cheaper to use the propeller proto board than a BOE+stamp [noparse]:)[/noparse]
Post Edited (rePete) : 7/12/2007 1:30:41 AM GMT
500 x 375 - 149K
640 x 480 - 91K
Comments
Do you log the operations somehow?
Just manual logging - right now I log type, volume, ambient temperature, time to the start/finish of 'first crack', time to the start/finish of 'second crack' and the time I stopped the roast (see http://www.sweetmarias.com/instruct.basic.html for explanations). This is also where the inspiration came from http://www.sweetmarias.com/homemade-homeroasters.html, there is a similar SX project around as well http://forums.parallax.com/forums/default.aspx?f=21&m=133939&g=135529
Do you mean a log of the measured temperature vs. time? I don't digitally do any logging. Would like to have the capability to download the roast history from the roaster to a file that I could add to the notebook for that roast but I'm not that advanced yet w/ the stamps. Be interesting to see how much time the heater was on for a particular bean. hmmmmm, maybe I have more work to do [noparse]:)[/noparse]
Post Edited (rePete) : 4/3/2007 3:14:24 AM GMT