Hysteresis.. How to do it??

[mackrackit]

I think the answer to you problem would be to make fan1on a loop not a return.

Stay in that loop until the temp drops below the set point.

Move the ADC commands to a GOSUB and then you can sample from anywhere and have less code.

This example is using two probes on a 18F4320.

CHECK:
T1 = temp1*2
T2 = temp2*2
LCDOUT $FE,1,"INSIDE ",#T1
lcdout $FE,$C0,"OUTSIDE ",#T2
gosub getT1
gosub getT2
if T1 > T2 + 10 then BLINK
goto CHECK

BLINK:
LCDOUT $FE,1,"INSIDE ",#T1
lcdout $FE,$C0,"OUTSIDE ",#T2
high PORTD.0
LOW PORTD.1
pause 100
low PORTD.0
HIGH PORTD.1
pause 100
if T1 = T2 THEN DARK
gosub getT1
gosub getT2
goto BLINK

DARK:
low PORTD.0
LOW PORTD.1
goto CHECK
getT1:
ADCON0=$1 '%00000001 AN0
gosub getAD
temp1 = ADRESH
return

getT2:
ADCON0=$5 '%00000101 AN1
gosub getAD
temp2 = ADRESH
return

getAD:
pause 50
ADCON0.1 = 1
pause 50
return

end

[Ioannis]

Also you could use a variable as a hysterisis.

hyst_high var byte
hyst_low var byte

hyst_low=0
hyst_high=0

....
....

if temp >= 80+hyst_high then gosub fan1on ' fan ON at 80
if temp <= 70+hyst_low then gosub fan1off


fan1on:
hyst_high=5
hyst_low=0
...
...
return

fan10ff:
hyst_low=5
hyst_high=0
...
...
return

Ioannis

[hoopstar]

I think the answer to you problem would be to make fan1on a loop not a return.

Stay in that loop until the temp drops below the set point.

Move the ADC commands to a GOSUB and then you can sample from anywhere and have less code.

I do plan on using GOSUB's but at the moment I am using the demo version of PicBasic and can't really afford to step up to Pro (poor student) so am just qualifying my code/ideas within the line limit of the demo version.

I *really* appreciate all the help and input on this - thanks guys.


Hoops