<= error

[davidwf]

Trying to use this simple function

.....other lines & checks
IF current_temp <=min_temp then: do something .............: endif
....other lines & checks

only proceeds if the current_temp is below min_temp, if it is = to then it doesn't do anything.

Have I missed the obvious ?

Thanks in advance

 

[westaust55]

Which version of the Programming Editor are you using?

Is the problem seen in the PE simulator, in the actual PICAXE chip (which one) or both?


Edit:
I tried the code:

FOR b0 = 1 TO 7
  IF b0 <= 5 THEN
    SERTXD ("<= 5")
  ELSE
    SERTXD (">5")
  ENDIF
NEXT b0

in the PE simulator for 08M, 14M, 20M,18X, 28X1/40X1 and 28X2/40X2 and it worked correctly for each PICAXE type selected.

Can you post the actual program code you are using.

 

[hippy]

I've never known <= not to work so the additional information westaust55 asks for would be helpful, also what values are in 'current_temp' and 'min_temp' ?

Posting you complete code may help. Is it a case of dealing with negative numbers ( negative temperatures ) which are actually represented by positive values ?

 

[davidwf]

Thanks for the prompt replies......it is my good old fridge thermostat controller, code attached as requested, code in question is on lines 117 to 122.

I am using the latest programming software (5.2.10) and a picaxe 08m

I appreciate the code is a bit messy but it works well and I am not up to speed enough to tidy it up....like I said it does work correctly apart from the anomoly mentioned.
Code is set to switch the compressor on at 5.0 deg C but it doesn't happen until 5.1, likewise it should go off at 3.5 deg C but stays on until temp drops to 3.4.
I appreciate that I could change these settings but I am intrigued as to why it doesn't switch at the = temps.

Just had a thought....yes, it does happen sometimes....Could it be because the code in line 129 / 130 isn't working it out accurately enough perhaps ??

Thanks again
Dave F

 

[hippy]

Code is set to switch the compressor on at 5.0 deg C but it doesn't happen until 5.1, likewise it should go off at 3.5 deg C but stays on until temp drops to 3.4.

I suspect it's a 'logic error', similar to "turn off when <= X" but implemented with "keep on when > X" but erroneously being written as "keep on when >= X" or something like that, and similar for the other conditional.

Best bet is to run it through the simulator, force the temps to be those which cause a problem and see where the code goes to and why.

 

[westaust55]

David,

Firstly, not the problem but PE is now at V5.2.11 (not 5.2.10)

Secondly, you problem appears at fist glance to be in the lines you suspected.

 	IF current_temp >[B][COLOR="red"]=[/COLOR][/B]min_temp and current_temp <=max_temp then: high green_led: [B][COLOR="Blue"]goto main[/COLOR][/B]: endif	; temp is within limits, leave "as is"
 	IF current_temp <[COLOR="Red"]=[/COLOR]min_temp then: high green_led: goto compressor_off: endif; Temp is at or below cool_temp, turn compressor off
[code]

So on an equals ( [B][COLOR="Red"]=[/COLOR][/B] ) situation you go back to the label [B][COLOR="Blue"]Main:[/COLOR][/B]
and thus  will never reach the next line with the [B]<=[/B] test if current_temp = min_temp

 

[SAborn]

Dave F,

I would just like to say how nice it is to see your code using symbols for your variables.

It is something that is often lacking here, and i for one do enjoy reading code that makes some logical sense as you read through it.

Well done from that aspect.

 

[davidwf]

westaust55 :
Thanks for the tips - I am now at 5.2.11

I just edited line 121 and I "THINK" it is correct....


saborn :
thanks for the feedback....as a beginner ( ) I find it easier to follow and, to me at least, more logical to use variable names rather than meaningless symbols ....that way I have an idea what it should be doing.
Likewise listing all the available variables at the top of the program ensures that I don't use the same one twice un-intentionally......we call it "belt and braces" over here