I haven’t had a lot of time to work on this project lately. A few weeks ago I had ordered a variety of jumper/header crimp pins, housings, and tools to crimp with. With those ends I’ve pieced together “arduino compatible” wiring harnesses to go between break out boards, arduino and to the perfboard and other pieces I’ve thrown together. As a result I feel I am now approaching a rough prototype roast controller.
One of my other purchases was a “Crib for Arduino” to mount some of the pieces inside a box that were not already part of the RadioShack case pictured in my last blog entry. Most of the crazy wiring on the Arduino photo has been woven together into separate bundles and connected directly to the DB25 connector cable which I’ve also been slowly crimping together.
I would have been testing the fan and heat controls last weekend (and when I had time this week) except that when I finally got it hooked up the fan and heat were no longer “smooth” but instead stuttered all over the place. It had been quite a while since I had the Arduino side of it hooked up to the mains power so I had to go through and double check all the wiring in the harnesses and DB25 hookups. Eventually I figured I’m either overloading it with the service schedule on reading sensors and writing to SD, updating the screen and not having time to trigger the mains voltage properly or else the timer wasn’t triggering properly.
Once I had confirmed all the wires were right I looked up the interrupt lines and timer lines in the Arduino website and realized the code probably had the wrong interrupt in there. Several months ago while trying to clean up some of the code I remember having accidentally typed over the interrupt number in the attachinterrupt line and saved it without realizing it had been modified while updating other code. Once I returned it back to the proper interrupt for the pin I was using everything worked again.
Tonight I tried running a load of beans through the roaster on fan only. I believe my adjustments for the fan power are slightly off because the beans begin moving a tiny bit too far into the % potentiometer. I’ll need to try running beans in an unmodified roaster and pay attention to the level of movement in both roasters based on the position of the knob. If I had some sort of manometer it would probably help more but I don’t have one. There are several DIY projects that appear to have built one that I’ve seen months ago that I might end up trying to look up again but I’ll have to see how well it goes without it.
This weekend I’ve got other things going on so it will probably be over the next week and following weekend that I try to calibrate the fan and then the heater. Once I’ve accomplished both things I’ll begin testing the PID settings to see how well I can control everything to automate the roast
Once the automation appears to be working I do want to add a few additional sensors still. I then will start working on an Arduino to PIC32 conversion of the controls adding the touch screen and using it to send instructions to the Arduino. Then slowly migrating more and more sensors and devices back over to PIC32 until eventually I’ve eliminated the Arduino unless it proves helpful to have separate microcontrollers for specific functions. There will probably be a basic Arduino compatible roast controller in between that will be built onto a PCB that will be professionally produced using one of the quick PCB prototype companies.