SWE3 Information

This is a small module to enable your 1-Wire network to sense relative humidity.

This module consists of a Honeywell HIH-4031-001 sensor, a DS2438Z smart battery monitor chip (to interface the sensor to the 1-Wire network), two RJ45 sockets, a two screw terminal blocks, two diodes, two capacitors, a resistor and a jumper and is available as either an assembled module, kit of parts or as a bare PCB.

The PCB is 55x40mm. The RJ45 sockets overhang by around 1mm. The module is 20mm high. There are 3mm mounting holes 3mm in from each corner which gives them spacings of 49x34mm.

Please be aware that the HIH-4031 and DS2438Z are surface mount components and that you should only order the kit of parts if you are confident you are able to solder these in place without damaging them or the PCB.

As this sensor is a version of the most commonly available design it is compatible with almost all 1-Wire software that supports humidity sensors, including digitemp, OWFS and many others.

The RJ45 sockets allow you to connect the sensor inline in a network built with standard cat5 network cables without the need for any tools. They are wired to the common standard as described on our wiring information page.

The row of three screw terminals allow you to wire bare cables into the sensor if you prefer to make your connections that way. As of PCB version 3.0 (shipping from around May 2016 onwards) the row of four screw terminals also allow direct connection to the VAD, VS+ and VDD pins of the DS2438Z IC allowing you to use the SWE3 as a general purpose ADC instead of a humidity sensor. It is available in a version without the sensor if you wish to use it for this.

The VDD screw terminal is connected to the power supply line for the DS2438Z and HIH sensor. What this is connected to depends on the position of the jumper. In "External" mode, the VDD line is connected to the +5V screw terminal and pin 2 of the RJ45 sockets. In "Parasitic" mode, the VDD line is a parasitically generated supply derived from the 1-Wire data line by D1, D2 and C1. The VS- pin of the DS2438Z is connected on the PCB to ground.

The jumper allows you to select the power mode for the sensor. Most people will use the parasitic power option but if you prefer you have the option to feed a seperate 5V supply to the sensor. This can be done either via the RJ45 connectors or the screw terminals.

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