Super Easy PC Control of 110 Vac using a Crydom Solid-State Relay

Step 2 Python Test Code

Below is the magic Python code. Again, can't get much easier than this. I've also attached the code in a file called "Test.py".

import sys, serial
from time import sleep

COM_PORT = 7
BAUD = 9600

ser = serial.Serial( COM_PORT-1, BAUD, timeout=0.5, rtscts=0 )

# Toggle the DTR pin on for 15 seconds, then off for 5 seconds.
while ( 1 ) :
print "On"
ser.setDTR( 1 )
sleep( 15 )
print "Off"
ser.setDTR( 0 )
sleep( 5 )

Comments

[cgrooms]

Thanks, I fix that problem now I have this error File "temp.py", line 7, in ser = serial.Serial( COM_PORT-1, BAUD, timeout=0.5, rtscts=0 ) File "/usr/lib/python2.6/dist-packages/serial/serialutil.py", line 166, in __init__ self.open() File "/usr/lib/python2.6/dist-packages/serial/serialposix.py", line 175, in open raise SerialException("could not open port %s: %s" % (self._port, msg)) serial.serialutil.SerialException: could not open port 6: [Errno 2] No such file or directory: '/dev/ttyS6'

[jimk3038]

Looks like your trying to open a serial port that does not exist. The easiest thing to do is to use another terminal program to verify which ports are available on your machine. Make sure the terminal app can successfully open the port - if the terminal app can't open the port then Python will also fail by throwing the exception you see in your error message. Edit the known good port name into the Python code and you should be good to go. Good luck, Jim

[cgrooms]

having the same problem getting errors File "test.py", line 8 print "On" ^ IndentationError: expected an indented block

[jimk3038]

Sorry to hear your having problems. The Indentation Error is a common error.

Python is kinda weird, in that, it's really picky about indenting in the source code. It drives Python crazy if you happen to indent with tabs and spaces within the same file. Either use spaces, or tabs, but never both in the save file. Some of the better editors have the ability to show tabs with special visible characters. Using this special mode you can verify you have not mixed spaces and tabs. To execute a block of code within some loop like a "while" loop, Python looks for an extra level of indention. The syntax would look like the following.

while 1:

print "Hello World"

This loop would print forever to the console simple because "print" is indented under the "while" statement.

Help this helps,
Jim

[Crimson-Deity]

I can't get this to work. All I get is a
errors.

[jimk3038]

What error are you getting? What line number does it complain about? Can you capture the error message and post it?

[Crimson-Deity]

Thanks for the quick respons ! :D

I have never, ever programmed ANYTHING before so I'm a noob to the max. Could you make a tutorial on how to use Python? I tried to copy and paste the "Test.py" content into the IDLE Python text thing, but some sort of error occured. My laptop is somewhere out of my reach at the moment so ill post a picture ASAP.

[jimk3038]

You have made a good choice with Python as a starting language. Python is kinda like a Swiss Army Knife for programmers. Python can be used to code really simple stuff. Or, full blown object oriented code.

Anyway, step number one - go out and buy two books. Learning Python and Python Cookbook. These are really good to get you jump started. I've attached a picture of my two books. You can see my books are kinda beat up - that is a good sign - means the books are used a lot!

Next, try to run my little code block. I'm guessing your missing the extra serial port package. Python does not have support for serial ports by default. No problem - go back to my instructable and download the extra installer for the serial port package. This package adds serial port control to Python.

Next, run each line of code in IDLE. IDLE will tell you when you hit a problem. But, once you install the serial port package I guessing you won't have any problems.

Good luck,
Jim