Multilevel Temperature control

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

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. 

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. 

Seems like it was more Roger than me. He provided the meat of the solution. I just gave some OS pointers. Glad it worked out for you.

Mike

BTW, if you ever type

ls -al

you see something like

drwxr-xr-x  4 mconners mconners 4096 Feb 12  2015 .

drwxr-xr-x 14 mconners mconners 4096 Nov 20 13:53 ..

-rw-r--r--  1 mconners mconners  553 Feb 12  2015 foo.cs

-rwxr-xr-x  1 mconners mconners 3584 Feb 12  2015 foo.exe

the first character  d indicates that it is a directory

. is the current directory

.. is the parent directory

-rw-r--r-- means  that the file is read/write for the owner,read only by the group, and read only for world (everyone else)

-rwx-r-xr-x means read/write/execute for the owner, read/execute for the group, and read/execute for the world

this pattern of rwx can be set on a file using the chmod command, where each set of rwx is an octal digit

so 755 = 111 101 101

which translates to rwx r-x r-x

so that's what the chmod 755 did

and the ./program means execute program in the current directory

Mike

Mike,

You're going too fast with the binary stuff.

On chmod you specify three digits. FIrst is for owner, second for group, third for others. Common values are: 6 for "read-write". and 4 for "readonly". when the file is a program that is executable, the numbers are 7 for read/write (and execute) and 5 for read-only (and execute).

This leads to the following common combinations. 644: read/write for the owner, and readonly for group and others.

Or 664 for read/write for owner and group, readonly for others.

For executable programs those combinationsbecome 755 for only owner can write and 775 for group can write as well.

On "ls" the 644 is shown as rw-r--r--, 664 is shown as rw-rw-r--, 755 is shown as rwxr-xr-x and 775 is shown as rwxrwxr-x.

I'm not going to tell you that some people ignore the rules and specify 4 digts to "chmod": 4755.

Yeah, you might be right, Roger. I do that sometimes. At least I didn't tell him about the extra bits like you did.

Between the 2 of us, I think we have it covered.

Mike

Subject: Re: [Raspberry Pi] - Multilevel Temperature control

here is an Arduino library for the 6675

https://github.com/adafruit/MAX6675-library

and here is some code using wiring pi

WiringPi for Raspberry Pi and MAX6675 thermal-couple sensor

I'm not familiar with either of these modules, so I can't really help you there. They were just what came up when I googled

MAX 6675 library

I also don't have a 6675 so I can't really help debug them.

Mike

Hi Terry,

Good to hear that it works. :-)

I have a little project with a MAX38155. I have not looked into the compatiblity with the older 6675 chips.

But Maxim is inclined to keep the protocols the same as much as possible. Many people who for example know the 6675 chip, will decide: "We can just as well use the TI chip instead of the Maxim one, if we have to rewrite the software". So Maxim is interested in keeping the protocol the same. "only minor changes" or "no changes at all".
So find the datasheets and try to see for yourself if they are the same. After you've made a decision, you're welcome to post again including your verdict and with links to both datasheets. Then it's easy for me to verify your claim.