Multilevel Temperature control

You could use cron job to execute a program to send a signal to your temp monitoring program to have it change monitoring modes.

So in other words your program would run, monitoring the temp for 200 degrees, then it would receive a signal (like SIGUSR1) from the cron job, then it would switch to the cooling phase, then receive another signal from a second cron job, and switch to the 3rd monitoring phase, then receive a final signal that would terminate the program.

So, look for Signals and Interrupts, and Cron for detailed instructions. This would probably be the easiest solution, with the least amount of coding. Plus you wont be busy waiting your pi the whole time, and wont need to worry about overflows on you timer.

Mike

I would separate the "execution" and the planning parts.

The planning part then again splits into an execution and a planning part.

The execution part of planning is executing a ramp, which in bash would look like:

#!/bin/bash

# this program is called "do_ramp"

starttemp=$1

endtemp=$2

tottime=$3

curtime=0

step=1

 

 

curtime=0

while [ $curtime -le $tottime ] ; do

  curtemp=`echo "$starttemp*($tottime-$curtime)/$tottime + $endtemp*$curtime/$tottime" | bc`

  echo -en $curtime $curtemp '\r'

  echo $curtemp > the_temperature_file

  sleep $step

  curtime=$[$curtime+$step]

done

The planning part of the planning program then becomes (again in bash):

#!/bin/sh

# Name this for the profile you are intending to make.
# It should be able to find the "do_ramp" script above in the current directory.
# slowly go to 200 over 6 hours

./do_ramp 70 200 `expr 6 \* 3600`

#stay there for 15 minutes.

./do_ramp 200 200 900

./do_ramp 200 124 `expr 4 \* 3600`

# etc...

The "execution" part of the whole thing is what you already have, but now it reads the "the_temperature_file" for the setpoint every few seconds or so.

I really like your approach Roger and I thank you for getting back to me so quickly.   I have had a couple of issues with your script and wonder if you could help me out. I have the following questions: 

1  When I put your script into Python 2, it did not like the $ on the the variables, so I removed them and all went well.

2. it does not like the -le, just after the while loop, changing that to curtime-tottime lets it work. 

3. should the curtemp statement be all in quotes, or should we be allowing that calculation? 

4.  I cannot get this one working in any way. 

curtemp=`echo "$starttemp*($tottime-$curtime)/$tottime + $endtemp*$curtime/$tottime" | bc`

  echo -en $curtime $curtemp '\r'

  echo $curtemp > the_temperature_file

  sleep $step

I have tried -e, -en, -ne, brackets, ., and all I can think of but I cannot get python to accept it in any manner. 

Please let me know where I am going wrong, as I believe this solution should work well.  Once again, thanks for your help. 

Roger's script was in bash, not python, and I agree with his approach. I misread your original question and thought you had completed the temp control part, but just needed a way to accurately trigger the execution. I was trying to accomplish the same thing roger was, separating execution from logic.

BTW, bash is the Bourne Again Shell, and it is the default command line interpreter when you login to your pi.

So you could copy the code roger gave you when saved in a text file will work just by changing the execute permissions on the file and typing it's name on the command line.

the first line

#!/bin/sh

or

#!/bin/bash

tells the CLI to execute the program as a sh script or a bash script, it's just as if you were typing the commands one at a time on the command line.

Mike

Mike thanks for the note this morning.  I tried with the #!/bin/bash as you suggested.  Should I be concerned that it stays red like a comment?  When I go to the variables, it does not like the $ signs.  Are they to be left in?  When I get to the While loop, again it will not take the $ but if I take them out I get a Syntax error on tottime, if I put them in, I get a syntax on the $.  I have tried both from Python2  and from the monitor, but I just keep getting the syntax errors.  Is there something that I am doing wrong?

I'm not sure what editor you are using, if it is a python specific editor it may show errors, but it should be fine. The $ should be in there.

you may need to do

chmod 755 <filename>

to change the permissions on the file, then execute it by typing

./filename

where filename is whatever you named the file.

Do a quick google search on unix shell scripting

look for a hello world type program and using command line arguments and variable in shell scripts.

Mike

Mike thanks for the info, that did help.  The script will now run but I get the following errors: 

1.  Line 12 the While loop start [0,: command not found

2.  do_ramp command on line 36, 40, and 42 : command not found

If I can get this running, is there a way to integrate it into my Python temperature control program, or just continue to run it as here? 

Thanks again for all this help. 

Terry

Roger & Mike:  I got the loop to work by putting another set of brackets around the curtime -le While loop as long as I made sure that my curtime was less than my tottime and I took the $ off tottime.  Only issue now is that with a difference of 10 I get 10 errors as curtime steps up from 100 to 110 to become equal to tottime.  Errors are unexpected end of file on line 17  while looing for matching ' ' and unexpected EOF on line 18 echo -en read line. Can you see what the problem is here now.  Still looking for my do_ramp command. 

Thanks for all your help guys, I think we are getting close.

Hi Terry,

When I cut-paste the program I wrote for you from this page into a file, it works first time. Exactly as written.

So you must have made a copy-paste error or something like that. It's very hard to debug something like that if I can't see what I'm doing. (my source, apparently changed on your computer).

To debug run the program with

   bash -x do_ramp

then you can usually see what it is tryting to do.

the first program I wrote should be called "do_ramp". The easiest to "find" it is to change the calls in the other program to "./do_ramp" )

Mike:  Just wanted to thank you for the help you gave me in getting this temperature control going.  I did get is working, but thanks for the Chmod info, sure did the trick.  Want to than both you Roger for your help.   You both did very well, considering what you had to work with on this end.