Saturday, July 09, 2011

On a cold day, a small shack is a big plus

It feels very cold here in Sydney at the moment. My workplace is sometimes overly hot which got me interested in measuring, and plotting, the temperature.

My radio shack is cupboard size and has a small fan heater in it which very quickly warms the space. But just how quickly…

Heater

A while back I built a PIC based thermometer that reads a Maxim 1-wire temperature sensor and sends the readings out a serial port at 9600 baud.

Device

USB serial cables seem to just work out of the box on linux these days:

Serial port

A little bit of python using pyserial to read lines from the serial port and log them to a text file suitable for reading in to a spreadsheet.


#!/usr/bin/env python
"""Utility to log temperatures from a serial device.
"""

import serial
import time

LOGFILE = '/tmp/temperatures.txt'

ser = serial.Serial('/dev/ttyUSB0')
log = open(LOGFILE, "a")

line = ser.readline()
while line:
logline = "%s\t%s\n" % (time.ctime(),
line.split()[0])
log.write(logline)
log.flush()
line = ser.readline()


Here's a bit of the log file:

Sun Jul 10 14:31:07 2011 28.0
Sun Jul 10 14:31:09 2011 28.5
Sun Jul 10 14:31:11 2011 28.5
Sun Jul 10 14:31:13 2011 28.5
Sun Jul 10 14:31:15 2011 28.5
Sun Jul 10 14:31:17 2011 29.0


Here is the temperature in my shack from window close to toasty warm.

Temperatures

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