23 April 2011
Uploaded video of the calibration routine used to adjust for overshoot.
22 April 2011
First demo showing software control of the reflow controller. A PID routine is not used in this version of the firmware but hysteresis is used. The routine works pretty well but needs some adjusting. You'll notice a couple of dips in the chart at the point when the phase is about to transition or when the oven is turned back on. This happens because there is a stock fan in the oven used to even out the heat flow. The temperature in the oven drops a bit when the fan is first turned on. Still, the process works pretty well without a PID routine. The software is not finished..still have a few more bits to add.
Below is a picture of the process exported to an excel spreadsheet. The chart shows the measured value, expected value, and heater on/off control. Overshoot is controlled pretty well but there is some undershoot happening when the fan kicks on inside the oven when it is turned back on. I'll need to figure that out and maybe adjust for it when I finish the PID routine.
I updated the elapsed timer routine after finishing this video so that the total process is measured. I should have the software completed this weekend and the first version of the firmware completed later this week. I’m hoping to do some test boards next weekend.