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Distributed Temp/Humidity Logging
Description
A low-cost method to monitor and log temperature and humidity measuremnts over a wide area based on the 1-wire system. Consists of an RS232 or USB interface, TAI8540 Temperature/Humidity units and RJ11 cable. FREE Software for Windows or Linux systems is available that allows monitoring, logging, charting of temperature/humidity readings. Stand-alone dataloggers also available when a PC is unsuitable.
Background
The 1-Wire network protocol was developed by Dallas Semiconductor(now Maxim) as a way to interface to range of small 1-wire devices. Every 1-Wire device contains a unique identifier preset at the factory. As the name suggests, the devices are networked together by a single wire that acts as a physical medium to communicate between a host and a large number of devices attached along the wire. It is also capable of powering these devices through the same wire. In practice, a second wire is actually needed to provide a return to ground and complete the circuit and most 1-wire units actually use a 4-wire RJ11 cable. The 1-wire protocol was originally concieved for short range circuit-board uses, but it was soon discovered that the system was ideal for connecting 10's of devices over 10's of meters. It is even possible to have over 200 devices spread over 100's of meters, but some precautions need to be taken. Maxim have written an application note describing this >>. There is also an application note for building ultra-reliable networks >>.
Measuring Temperature and Humidity
To construct and 1-wire temperature/humidity network you require; An RS232 or USB interface - these convert from common PC interfaces to the 1-wire protocol. Temperarure and/or Humidity Modules. Each small unit contains a 1-wire interface and a temperature and/or a humidity sensor. They are provided with 2 RJ11 connectors - in and out, and many units can be connected together using RJ11 cable in a serial fashion. RJ11 Cable - available in 3m, 10m and 20m lengths. Windows or Linux software on your PC
Modules
TAI8540D Temperature/Humidity Module	0% to 100% RH range Measures Relative Humidity with a ±2% accuracy Temperature measurement accuracy ±2°C 1-Wire® DS2438 IC 1-wire in and 1-wire out RJ11 connectors All power supplied via 1-wire cable Unique 1-Wire address permits multiple sensors on the network TMEX -Standard compatible User Manual >>
TAI8520 Temperature Module	-50°C tp 55°C temperature range indoor use only ±0.5°C resolution 1-Wire® DS18B20 IC 1-wire in and 1-wire out RJ11 connectors All power supplied via 1-wire cable Unique 1-Wire address permits multiple sensors on the network TMEX -Standard compatible User Manual >>
DS9490R USB to 1-wire Adaptor	The DS9490R is a USB bridge with 1-Wire RJ11 interface Accommodates 1-Wire receptacles and networks Can be used with any of the 1-Wire modules.
DS9097U RS232 to 1-wire Adaptor	Sophisticated RS232 to 1-Wire Adapter Performs RS232 level conversion and actively generates the 1-Wire communication signals Can be used with any of the 1-Wire modules.
Connection Cables A range of ready made cables with RJ11 cables in common lengths 1WC-3M 1-wire cable 3M RJ11 1WC-10M 1-wire cable 10M RJ11 1WC-20M 1-wire cable 20M RJ11
FREE Software
Software Development kits >> 1-wire Public Domain Kit - A public domain API written in C and designed to be portable across multiple PC operating systems, handheld operating systems, and microcontroller platforms. The kit contains 18 sample 1-Wire applications written in C. For microcontroller platforms without an available C compiler, the kit also includes assembly code functions representing low level 1-Wire bus protocol algorithms such as reset/presence detect, byte I/O, and bit I/O.
1-wire SDK for Windows - This SDK is aimed primarily at PC host environments running Microsoft Windows. Both the 1-Wire drivers and SDK for Windows are available for downloading. The kit contains sample programs (in VB, C, Delphi, JScript, etc.) and HTML documentation for utilizing the TMEX API and the 1-Wire COM object. The 1-Wire drivers download contains optional support for Microsoft's .NET platform The OneWireViewer utility is also offered to demonstrate 1-Wire devices. 1-wire API for Java - The 1-Wire API for Java is the foundation for developing robust 1-Wire and iButton software on platforms that have a Java Virtual Machine. It includes the above-mentioned OneWireViewer utility and its Java source code	Sample shots from the 1-wire Viewer
LogTemp - Temp/Humidity Charting and Logging Logs and charts Temperature and Humidity Service version also available - no user log-in required Can launch programs and email alerts on alarm Also supports SMS Text via Commercial gateway Access via HTML, FTP, email For use with TAI8520 and TAI8540 More Info and FREE Download >>
Thermometer - Temperature Charting and Logging Logs and charts Temperature High and Low Alarm facility Chart, LCD and dial gauge displays User graphic screens with temperature overlay For use with TAI8520 only More Info and FREE Download >>
DigiTEMP - Linux based Temp Charting and Logging For use with TAI8520 and TAI8540 For use with Linux Charts and Logs data More Info and FREE Download >>
Standalone Datalogging
LOG08-II Stand Alone 1-wire Datalogger LOG08-II is a stand-alone 1-Wire interface that provides the ability to record up to 3 years of readings from a variety of 1-Wire sensors. The records are stored on LOG08-II until you require access to them. At any time in the recording process, you can download the records to your PC, via a standard RS232 serial interface. The records are conveniently output as comma separated entries and can easily be imported into Excel or other standard PC programs.
Standard RS232 serial interface between the 1-Wire bus and a host PC provides real-time relief for the host PC by removing the burden of providing the precision timing required by the 1-Wire bus No connection to PC required for stand-alone logging Supports the TAI8540 and TAI8520 sensors Easy option programming (Set and Forget) - NO option jumpers required. Capability to interface up to 60 different sensors On-board analogue voltage input Connectivity to 1-Wire bus via either terminal strip or RJ-12 connector Large EEPROM capability for sensor logging Discrete commands for setting all important parameters Battery backed up Real Time Clock for displaying time of day with results of sensor polls or logs PCB Size fits into optional PacTec CM5-125 case EASY software upgrades via recyclable processor changes	User Manual >>
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