Soldering station

[Archangel]

Hi Fratello,
You REALLY like those Nokia graphic LCD . . .
I think they're pretty cool too, Now as for USEFUL comments . . . According to the engineer from France who writes the Dark Side column in Circuit Cellar, . . Robert La Coste ? his suggestion is to use a PID loop to give you some Hysteresis to your temperature to prevent overshoot and undershoot of tip temp. Search the forum there is a pretty good one or more in circulation.

[fratello]

Thanks for advice !
I found this : incPID_mc.pbp Author : Henrik Olsson. GREAT WORK !
Unfortunately the code don't fit in my small 12F675 ; it's a solution to upgrade to a bigger PIC (18F2550 ?) but... for my small device it's another way ?!
...and yes, I like this display : it's verry cheap (about 1 euro) and easy to use. One 2x16 LCD display it's 6 euro and don't look so nice .

[Jerson]

I can assume you're almost at the limits of the code space with your current code. The best option, I reckon, to get reasonably good control with your existing setup would be to try PI control. As it is, you are using the PWM function. Just compute the proportional output to get a smoother control.
Modify your check routine so that the PWM function outputs 255 when far lower than the setpoint, 0 when at it. Now, to compensate the offset of the temperature, you add the integral correction over time. This can be achieved quite easily with integer math alone.

A typical P controller pseudo code
Band con 10 ' this decides the band around SetPoint in which you want proportional control

if Temp < SetPoint-Band then
PWMout = 255 ' full heat
else
if Temp > Setpoint+Band then
PWMout = 0 ' full off
else
' within band, do Proportional heating
Error = SetPoint+Band-Temp ' you want to get the bigger numbers for temp < sv
PWMout = (Error*255)/(2*Band) ' get an output from 255 to 0 over the band from SV-Band to SV+Band, 50% at SV
endif
endif

Adding integral is relatively easy too. You just need a variable to adjust the error over time. Or use a button to snapshot the error and add it as an offset.

IntErr var byte

IntErr = IntErr+(Error/IntTime) ' integrate the error over time

PWMout = PWMout + IntErr
if PWMout > 255 then PWMout = 255 ' limit to usable PWM range

PWM Mosfet, PWMout, 300 ' transfer to the mosfet

Just some ideas.

[fratello]

Thank You so much ! I try and I post the results.

[fratello]

I cannot run my simulation ( AMD Athlon64 X2 DualCore 4200+, 2 GB RAM ?!) ...
It's this code OK ? Thanks !

hyst            CON  2
check:
if mode >= 1 then
    if w1 < calibra-hyst     then pwm mosfet, 255, 300
    if w1 > calibra+hyst     then low mosfet
    if w1 = calibra+hyst-w1 then pwm mosfet,(w1*255)/(2*hyst), 300
endif
return

[Jerson]

Looks good to me except I would make the first line this
if w1 < calibra-hyst then high mosfet

[fratello]

Because of "structure" of my code (see memo subroutine) , this procedure don't work ... I don't have anymore acces to "memory"... I must try a different way, but I have such little space.