for tuning i followed more or less the tutorial PID Without a PhD from Tim Wescott and the tutorial and video from PID Explained Team.

first i just checked with low temperatures of 20..40°C as i went on and tested up to 260°C i noticed that the current did decrease. and the temperature did not increase any more. i could see this in my graph as the heating got slower and slower with the rising temperature… (also the pid already saturated at the output..)

so i measured the resistance during the cool down of the heating elements to get some insights: (4x in series → 48V/4=~12V/Module)

result: the ~57W is not enough to get to more than 255°C…

i rearranged the Modules into 3-in-series connection. this means ~16V/Module – and tested again:

with this i found that i can go above 255°C.

i then tested the profile for the Felder ISO-Cream “Clear” and found that in the reflow stage the heat-up is a little to slow:

in the *my setup* picture is a temporary cardboard thing with a 80mm 12V fan (connected to 5V) to cool down faster between tests. for the final setup i think i will buy 1 or two 5V and PWM capable fans…. and also exchange the *chamotte* ston with some metal frame. this way i also can cool the bottom side..

so i again switch the configuration – now i have a 2-in-series config: 24V/Module CURRENTLY THIS TABLE IS ONLY CALCULATED VALUES!!

i also tested this with the Felder profile:

this time the heat-up is fast enough! 🙂 the nice and working pid tuning i had for the 4-in-series arrangement is now out of tune… so i will have to re-tune it to get less overshoot / swing.

while having a break i thought about the maximal power in this configuration – and found that this way i only be able to power 2×2 modules with my 250W power supply. for now i leave it this way. in the long run i hope with the other frame concept i get more heat to the pcb and less into the stone and this way be able to use the 3S config.

Tuning

after a day of mostly waiting til the system cooled down again – one test cycle <=60°C needs 400s → 6:40min – i just rebuild my hw mounting setup.

this way i can warm up quicker and cool down much quicker as i do not store heat in the stone. – at least that is what i hope..

hmmm – does not seem to change much..

i then tested the actual Felder Profile:

seems i have a working profile. i will add a little more time for the prepare phase. so the pcb is really fully at the 50°C. at the top i have a little bit of a mis-match – i saw on my temp sensor directly connected to the heating elements at the top ~265°C – so that is hot… the pcb seems to increase its temperature resistance at higher temperatures… at the peak i have 230°C to 245°C error. and to the heating this results in ~35°C difference…

i will report when i solder the first real board. 😉