Sensor3

temp sensors on USB

Edsard Boelen, 18 oktober 2008

Because rs232 ports are hardly found on new computers, and the BSD system has trouble detecting the old sensor, I decided to do another upgrade, now it operates via USB. The same sensors are being used though: the DS1820, the same graph method is used too. (if it works, don't break it)

View current graph here current list

The idea

Building a usb device is a bit complex, but good libraries can be found on the web these days I will use the following project as starting point: Arnold Beck's usb-ds1820
The device (Atmega8) will use 2 libraries: USB-lib from Christian Starkjohann and 1Wire impl from Peter Dannegger.
The client program will use lib usb from sourceforge and is based on arnold beck's software
The web visualization will use php, gd and phplot to generate the graphs.

DS1820:

The dallas 1820 ic is a temp sensor which uses the 1wire interface.

Atmega 8

I have created the folowing schematic:

the prototype looks as follows:

The code is from arnold beck with a few modifications: for atmega88 and a new usb driver. it can be downloaded here

Deamon

the code can be downloaded here

plotter

the plotter is still phplot, it took a while to get it working with OpenBSD though (gd-library needs to be compiled)