This project came out of my frustration with the refrigerator/freezer on my boat. It ran too much which was not only noisy but caused excessive battery drain. It turned out to be a two part problem, frost on the refrigerator evaporator and excessive temperatures in the enclosure were the refrigerator is located. To fix the frost problem I decided to add a heating element to the refrigerator evaporator to make a frost free refrigerator. The second problem could be solved by having fans moving air in and out of the enclosure either all the time or only when the compressor was running without using a controller. TO HECK WITH THAT! We have Picaxe! So if cooler air is available move it using fans.
Originally the project was just a monitor and fan program. When I added defrost I took over the thermostats. The original thermostats are still in place and can be back up and running by moving 4 wires. This sort of redundancy is also why I used separate inputs for the DS18B20 sensors. I can have spares but the reprogramming needed to swap might be a problem while on the water.
Sub procedures are in next post
Originally the project was just a monitor and fan program. When I added defrost I took over the thermostats. The original thermostats are still in place and can be back up and running by moving 4 wires. This sort of redundancy is also why I used separate inputs for the DS18B20 sensors. I can have spares but the reprogramming needed to swap might be a problem while on the water.
Code:
#picaxe 20X2
'refrigerator and freezer control program
'operates as two thermostats to control both the refig and freez compressors
'operates a heater on the refrigerator evaporator for defrosting
'operates a fan inside the refrigerator and another fan to cool the outside of the unit
'keeps statistics, min/max temps and duty cycles
'displays compressor run status, current temps and statistics on a LCD display
'logs date, time, timer, all inputs and more to a SD card
'constants
symbol RCutIn = 98 '-1 from the desired compressor cut in: -1C +30F (99 rescale)
symbol RCutOut = 89 '+1 from the desired compressor cut out: -12C +10F (88 rescale)
Symbol FCutIn = 79 '-1 from the desired compressor cut in: -20C -4F (79 rescale)
Symbol FCutOut = 73 '+1 from the desired compressor cut out: -28C -18F (73 rescale)
symbol DefFreq = 50 'number of compressor cycles (with AC on) before defrost
symbol DefTime = 110 'length of defrost cycle, with 10 sec loop 60 = 10 minutes ADD DefFreq to desired time!
symbol LCDbaud = t9600_8
symbol LOGbaud = t9600_8
'general vars
symbol RCtemp = b0 'refrigerator cabinet temperature sensor value
symbol REtemp = b1 'refrigerator evaporator temperature sensor value
symbol FCtemp = b2 'freezer cabinet temperature sensor value
symbol FEtemp = b3 'freezer evaporator temperature sensor value
symbol HTtemp = b4 'hold temperature
symbol BTtemp = b5 'board temperature
symbol RcomR = b6 'refrigerator compressor on=1 otherwise 0
symbol RDefCnt = b7 'refrigerator defrost counter
symbol FcomR = b8 'freezer compressor on=1 otherwise 0
symbol AC = b9 'shore power yes=1 otherwise 0
symbol Rmin = b10 'refrig min temp
symbol Rmax = b11 'refrig max temp
symbol Ron = w6 'uses timer for duty cycle calcs
symbol Roff = w7 'uses timer for duty cycle calcs
symbol Rduty = b16 'refrig on time duty cycle
symbol Fmin = b17 'see above
symbol Fmax = b18
symbol Fon = w10
symbol Foff = w11
symbol FDuty = b19
'display vars
symbol Tsign = b24 'current temp
symbol Ttens = b25
symbol Tones = b26
symbol Nsign = b27 'min temp
symbol Ntens = b28
symbol Nones = b29
symbol Xsign = b30 'max temp
symbol Xtens = b31
symbol Xones = b32
symbol Dxxxx = b33 'duty cycle, xxxx not displayed, used as a placeholder for bintoascii
symbol Dtens = b34
symbol Dones = b35
'DS1307 variables
symbol secs = b36
symbol mins = b37
symbol hour = b38
symbol day = b39 'day of week 1-7
symbol date = b40 'day of month 1-31
symbol month = b41
symbol year = b42
symbol control = b43 'only used in sub SetClock, could be molested
'DS1307 display variables
symbol yr10 = b44
symbol yr01 = b45
symbol mo10 = b46
symbol mo01 = b47
symbol dt10 = b48
symbol dt01 = b49
symbol hr10 = b50
symbol hr01 = b51
symbol mn10 = b52
symbol mn01 = b53
symbol sc10 = b54
symbol sc01 = b55
'input pins
symbol RCSense = C.0 'DS18B20 in refigerator
symbol RESense = C.1 'DS18B20 on refigerator evaporator
symbol FCSense = C.2 'DS18B20 in freezer
symbol FESense = C.3 'DS18B20 on freezer evaporator
symbol HTSense = C.4 'DS18B20 in hold area (hopefully cooler air)
symbol BTSense = C.5 'DS18B20 on main board
symbol ACpwr = pinC.6 'detect AC power for defrost cycle
'output pins
symbol RComRly = B.0 'relay for refigerator compressor (relay NO)
symbol FComRly = B.1 'relay for freezer compressor (relay NO)
symbol DefrRly = B.2 'relay for defrost (Switched 12VDC)
symbol RefFan = B.3 'fan inside refrigerator (Switched 12VDC)
symbol LCD = B.4 'arduino-direct.com LCD 1602 (apparently no longer available)
'i2c sda = B.5 'DS1307 RTC (Chronodot V2.1)
symbol Logger = B.6 'Seedstudio SDLogger
'i2c sda = B.7 'DS1307 RTC
symbol CabFan = C.7 'cabinet fan, run if cooler air is available (Switched 12VDC)
start:
high LCD
pause 5000
serout LCD, LCDbaud,("$CLEAR",13)
serout LCD, LCDbaud,("$GO 1 2",13)
serout LCD, LCDbaud,("$PRINT *BoatThermo9*",13)
serout LCD, LCDbaud,("$GO 2 3",13)
serout LCD, LCDbaud,("$PRINT LG 07/05/12",13)
high Logger
pause 10000 'wait for logger *WHEW*
serout Logger, LOGbaud,("*START* BoatThermo9.bas *START*",13,10)
serout Logger, LOGbaud,("Date,Time,Timer,RCtemp,REtemp,FCtemp,FEtemp,HTtemp,BTtemp,RcomR,RDefCnt,FcomR,AC",13,10)
high RefFan
'get temps, rescale and set min/max vars
readtemp RCSense, RCtemp
if RCTemp < 127 then
RCTemp = RCTemp + 100
else
RCTemp = 128 - RCTemp + 100
end if
Rmin = RCtemp
Rmax = RCtemp
readtemp FCSense, FCtemp
if FCTemp < 127 then
FCTemp = FCTemp + 100
else
FCTemp = 128 - FCTemp + 100
end if
Fmin = FCtemp
Fmax = FCtemp
i2cslave %11010000, i2cslow, i2cbyte 'set DS1307 slave address
' gosub SetClock 'uncomment to set RTC, set vars in sub
settimer t1s_8
main:
readi2c 0,(secs,mins,hour,day,date,month,year)
bcdtoascii year,yr10,yr01
bcdtoascii month,mo10,mo01
bcdtoascii date,dt10,dt01
bcdtoascii hour,hr10,hr01
bcdtoascii mins,mn10,mn01
bcdtoascii secs,sc10,sc01
readtemp RCSense, RCtemp
readtemp RESense, REtemp
readtemp FCSense, FCtemp
readtemp FESense, FEtemp
readtemp HTSense, HTtemp
readtemp BTSense, BTtemp
if HTtemp < BTtemp then 'get cooler air if available
high CabFan
else
low CabFan
end if
AC = ACpwr 'shore power? 1 if yes
serout Logger, LOGbaud,(mo10,mo01,"/",dt10,dt01,"/",yr10,yr01,",",hr10,hr01,":",mn10,mn01,":",sc10,sc01,",")
serout Logger, LOGbaud,(#timer, ",")
serout Logger, LOGbaud,(#RCTemp,",",#RETemp,",",#FCtemp,",",#FEtemp,",",#HTtemp,",",#BTtemp,"," ,#RcomR,",",#RDefCnt,",",#FcomR,",",#AC,13,10)
sertxd("RC: ",#RCTemp," RE: ",#RETemp," RRun: ",#RcomR," RDefCnt: ",#RDefCnt," * FC: ",#FCTemp," FE: ",#FETemp," FRun: ",#FcomR," AC: ",#AC,13,10)
' sertxd("A RC: ",#RCTemp," Rmin: ",#Rmin," Rmax: ",#Rmax," * FC: ",#FCTemp," Fmin: ",#Fmin," Fmax: ",#Fmax,13,10)
'rescale temps to get linear integer set across zero degrees C
'after rescale 10C=110 -10C=90
if RCTemp < 127 then 'refrig cabinet
RCTemp = RCTemp + 100
else
RCTemp = 128 - RCTemp + 100
end if
if RETemp < 127 then 'refrig evaporator
RETemp = RETemp + 100
else
RETemp = 128 - RETemp + 100
end if
if FCTemp < 127 then 'freezer cabinet
FCTemp = FCTemp + 100
else
FCTemp = 128 - FCTemp + 100
end if
if FETemp < 127 then 'freezer evaporator
FETemp = FETemp + 100
else
FETemp = 128 - FETemp + 100
end if
gosub RDisplay 'update the refrigerator line on the LCD
gosub FDisplay 'update the freezer line on the LCD
if RDefCnt < DefFreq then 'operate the refrigerator compressor
if RETemp > RCutIn then
if RcomR = 0 then 'runs once at start of refrig compressor cycle
if AC = 1 then
RDefCnt = RDefCnt + 1 'increment defrost counter
end if
Roff = timer - Roff 'duty cycle calcs
if Ron > 0 then
Roff = Ron + Roff
Ron = Ron * 100
Rduty = Ron / Roff
end if
Ron = timer
end if
if RDefCnt < DefFreq then 'prevent short cycle!
high RComRly 'turn on compressor
RcomR = 1
end if
elseif RETemp < RCutOut then
low RComRly
if RcomR = 1 then 'runs once at end of refrig compressor cycle
Ron = timer - Ron 'set duty cycle vars
Roff = timer
end if
RcomR = 0
end if
else 'defrost
low RComRly 'be SURE compressor and refrigerator internal fan are off
RcomR = 0
low RefFan
if REtemp < 101 then 'run heater until 1 degree above freezing
high DefrRly
else
low DefrRly
end if
RDefCnt = RDefCnt + 1 'use counter as a timer
if RDefCnt > DefTime then
RDefCnt = 0
high RefFan
end if
end if
if FETemp > FCutIn then 'operate the freezer compressor
high FComRly
if FcomR = 0 then 'runs once at start of freezer compressor cycle
Foff = timer - Foff 'duty cycle calcs
if Fon > 0 then
Foff = Fon + Foff
Fon = Fon * 100
Fduty = Fon / Foff
end if
Fon = timer
end if
FcomR = 1
elseif FETemp < FCutOut then
low FComRly
if FcomR = 1 then 'runs once at end of freezer compressor cycle
Fon = timer - Fon
Foff = timer
end if
low FComRly
FcomR = 0
end if
pause 9000 '10 sec total loop time
goto main
'*** CONTINUED NEXT POST ***
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