• on Test & Measurement
  • Published in issue 6/2008 on page 58
About the article

Thermo-Snake

a 128-channel USB’ed datalogger for a 1-wire thermal monitoring network

Thermo-Snake
It’s often necessary to monitor the temperature of different rooms. For example in a green-house with various kinds of plant, in a wine cellar, on a motor surface or simply in your home. There are commercial dataloggers designed for this but they come at a price. Here’s a DIY alternative with real-time monitoring and recording capabilities.
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Products
Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor Members can exclusively download these files for free as part of their Membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service. Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Extra info, Update

With some DS18B20 devices it may be necessary to lower the value of R2 to 2.2 kohm for the PIC micro to recognise the sensor and the PC software to enumerate it.

The DS1820 sensor does not work in this circuit due to a different device identifier word.

 

27 August 2008

A new release (v1.2) of NET-THERMO is available that fixes issues with negative temperature values and replaces the log file separator character. Also, during temperature monitoring you can view
the data packet in the StatusBar.

Resistors
R1 = 10k
R2 = 4k7 (possibly down to 2.2k)
R3,R4 = 330

Capacitors
C1 = 470µF 25V
C2 = 100nF
C3,C4 = 15pF
C5 = 220nF

Semiconductors
D1, D2 = LED, 3mm, low current
IC1 = PIC18F2550, programmed, Elektor SHOP # 070122-41
X1 = 20MHz quartz crystal
DS18B20 temperature sensor, quantity as required (max. 128

Miscellaneous
K1 = USB-B connector
K2 = 2-way SIL pinheader, lead pitch 2.54 mm
K3 = 3-way SIL socket, lead pitch 2.54 mm
PCB, ref. 070122-I from www.thepcbshop.com
PCB artwork file, free download # 070122-1.zip
Project software: PIC hex and source files, PC executable. Free download # 070122-11.zip
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