This article gives a quick overview of my first temperture logger. It is made from the PICAXE datalogger kit.

Specs:

• 4 Digital Temperature Sensors with 0.1 degree resolution.
• Handles positive or negative temperatures.
• Samples taken every 6 seconds.
• Records up to 29 hours of data from each sensor (simultaneously).
• Temperatures are displayed on the LCD screen, sent to the computer via serial and also stored in the EEPROM as each reading is taken.
• Data stored in the EEPROM's can be dumped to the PC at any time. When the dump is finished, the unit continues storing readings in EEPROM's from the same point it was up to before the dump was started.
• Can operate connected to a computer or standalone. I usually use it standalone and let it record the data by itself.

The code I wrote to give these features is available here.

To make the Data Logger I ordered the following bits and pieces from MicroZed in Australia:

• AXE110P   Data Logger
• AXE111    Memory Expansion Board
• AXE034    Real Time Clock Chip
• 24LC256   EEPROM  x 6  (assuming that the Memory Expansion Board comes with two chips already, for 8 total)
• AXE033    LCD screen

Connections (Left to Right in the picture, along the bottom of the unit):

1. Temp Sensor Wires
2. Power input (+5V Regulated)
3. Data Download (Dump) switch with built-in LED. Directly underneath that is the Data Download serial port.
4. Programming port.

The details of how I modified the standard PICAXE data logger circuit are available here.
 

Stu's Temperature Logger
Firmware Version 1.0
Initialising...Done!

Time:15:35:2   Mirror:+36.1  Tube:+36.0  Corrector:+36.0  Ambient:+36.2  
Time:15:35:8   Mirror:+36.1  Tube:+36.1  Corrector:+36.1  Ambient:+36.2
Time:15:35:14   Mirror:+36.1  Tube:+36.1  Corrector:+36.0  Ambient:+36.1  
Time:15:35:20   Mirror:+36.1  Tube:+36.1  Corrector:+36.0  Ambient:+36.0
Time:15:35:26   Mirror:+36.1  Tube:+36.0  Corrector:+36.0  Ambient:+36.1  
Time:15:35:32   Mirror:+36.1  Tube:+36.1  Corrector:+36.0  Ambient:+36.1
Time:15:35:38   Mirror:+36.1  Tube:+36.1  Corrector:+36.0  Ambient:+36.1  
Time:15:35:44   Mirror:+36.1  Tube:+36.1  Corrector:+36.1  Ambient:+36.1
Time:15:35:50   Mirror:+36.2  Tube:+36.1  Corrector:+36.1  Ambient:+36.1  
Time:15:35:56   Mirror:+36.2  Tube:+36.1  Corrector:+36.1  Ambient:+36.1

Starting Download...

Time Mirror Tube Corrector Ambient
15:35:2 +36.1 +36.0 +36.0 +36.2
15:35:8 +36.1 +36.1 +36.1 +36.2
15:35:14 +36.1 +36.1 +36.0 +36.1
15:35:20 +36.1 +36.1 +36.0 +36.0
15:35:26 +36.1 +36.0 +36.0 +36.1
15:35:32 +36.1 +36.1 +36.0 +36.1
15:35:38 +36.1 +36.1 +36.0 +36.1
15:35:44 +36.1 +36.1 +36.1 +36.1
15:35:50 +36.2 +36.1 +36.1 +36.1
15:35:56 +36.2 +36.1 +36.1 +36.1