Reflow oven with PID control

liyf · 发表于 2013-9-11 07:44:08

原文：
Hi guys ,

i' currently building a reflow oven with PID control with PICAXE 28X1.I'm using a standard pizza oven and using a relay to control the main power switch.
Since i'm still a newbie in regard of PID control and PWM, i have intergrate the PID control from greencardigan project 'coffee maker' into the source code of my project.

The oven should operate with this parameters
1.heat to 150°C and maintain for 40s
2.heat to 190°C and maintain for 10s
3.heat to 245°C and maintain for 10s
4. Cool down to room tempereature

the code is as followed:

symbol Kp = 1000
symbol Ki = 20
symbol Kd = 10
symbol dt = 1
symbol set_temp =w0
symbol set_time =b0
symbol sensor = 1
symbol cur_temp = w1
symbol cur_time=b1
symbol oven = 7
symbol led_hot =5
symbol led_hold =4
symbol err = b2
symbol pre_temp =b3
symbol INT_MAX = 1000
symbol PRO_MAX = 15000
symbol DER_MAX = 5000
symbol PID_MAX = 52768
symbol PID_MIN = 12768
symbol PID = w2
symbol x=b4
symbol input_button1= pinc.1
'#########################################################################################
INIT:
set_temp =0
set_time =0
PID = 49000
'#########################################################################################
Main:
do
low oven
low led_hot
low led_hold
if input_button1 = 0 then 'Waits in this loop until button1 is pressed
exit
endif
gosub get_temp
gosub Phase_1
gosub get_temp
gosub Phase_2
gosub get_temp
gosub Phase_3
gosub get_temp
gosub Phase_4
low oven
loop
goto main
'#########################################################################################
get_temp: 'Reads thermocouple
readadc10 sensor, cur_temp
return
'#########################################################################################
Phase_1:
set_temp =123 'set temperate at 150°C
set_time =40 'hold 150°C for 40s
if cur_temp < set_temp then
gosub get_temp
high led_hot
gosub PID_calc
gosub PID_control
endif
low led_hot
for cur_time=1 to set_time
gosub get_temp
high led_hold
gosub PID_calc
gosub PID_control
pause 1000
next cur_time
low led_hold
return
'#########################################################################################
Phase_2:
set_temp =156 'set temperate at 190°C
set_time =10 'hold 190°C for 10s
if cur_temp < set_temp then
gosub get_temp
high led_hot
gosub PID_calc
gosub PID_control
endif
low led_hot
for cur_time=1 to set_time
gosub get_temp
high led_hold
gosub PID_calc
gosub PID_control
pause 1000
next cur_time
low led_hold
return
'#########################################################################################
Phase_3:
set_temp =201 'set temperate at 245°C
set_time =10 'hold 245°C for 10s
if cur_temp < set_temp then
gosub get_temp
high led_hot
gosub PID_calc
gosub PID_control
endif
low led_hot
for cur_time=1 to set_time
gosub get_temp
high led_hold
gosub PID_calc
gosub PID_control
pause 1000
next cur_time
low led_hold
return
'#########################################################################################
Phase_4:
set_temp =20 'set temperate at 25°C
set_time =10 'go to 25°C to cool down
if cur_temp => set_temp then
gosub get_temp
high led_hot
gosub PID_calc
gosub PID_control
endif
low led_hot
return
'#########################################################################################
PID_calc:
gosub get_temp
if PID > 49000 then
PID = 49000
else
PID = PID
endif
if cur_temp <= set_temp then 'for negative errors
err = set_temp - cur_temp max 65 'error
w3 = Ki * err * dt max INT_MAX 'INTEGRAL..........................
PID = PID + w3 max PID_MAX
w3 = Kp * err max PRO_MAX 'PROPORTIONAL......................
PID = PID + w3 max PID_MAX 'Int + Pro
else 'for positive errors
err = cur_temp - set_temp max 65 'error
w3 = Ki * err * dt max INT_MAX 'INTEGRAL.........................
PID = PID - w3 min PID_MIN
w3 = Kp * err max PRO_MAX 'PROPORTIONAL....................
PID = PID - w3 min PID_MIN 'Int + Pro
endif
'if cur_temp > err then 'temp increasing
'w3 = cur_temp - err
'w3 = w3 * Kd max DER_MAX 'DERIVATIVE ......................
'PID = PID - w3 min PID_MIN 'int + pro + der
'elseif cur_temp < err then 'temp decreasing
'w3 = err - cur_temp
'w3 = w3 * Kd max DER_MAX 'DERIVATIVE ......................
'PID = PID + w3 max PID_MAX 'int + pro + der
'else
'w3 = 0 'no derivative part
'endif
'pre_temp= cur_temp
return
'#########################################################################################
PID_control:
for x = 1 to 1000 'Manual PWM with 1 second period (adjust pause at end of main routine to get 1 sec period)
if x > PID then
low oven
else
high oven
endif
pause 6
next x
pause 54 'Adjust to get timing right on PID mode (1 sec PWM period)
return
'#########################################################################################

复制代码

The PID controller seems to be not functioning. The oven will heat to 160°C and the picaxe will exit the program.
Can someone spot any mistake?

Thanks

grimmjaws

robter · 发表于 2015-10-22 21:52:07

感谢楼主提供这么好的东东

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Reflow oven with PID control

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