Temperature and Humidity Data Transmitter

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Temperature and Humidity Data Transmitter

USR-SENS-WSD-T/2/4 & HC-05 Bluetooth module
This Instructable describes a very simple Remote Temperature & Humidity data collection method.

The USR-SENS-WSD module provides the temperature and humidity data and the HC-05 Bluetooth module transmits that data. A Bluetooth serial port and application is required to receive the data.

The USR-SENS-WSD module is available in three versions -T,-2 or -4 corresponding to TTL, RS232 or RS485; The Bluetooth module is commonly HC-05 or HC-06 being configured as Slave (05) or Master (06). HC-05 is used here though I believe that the HC-06 can be reconfigured.

The Specifications are:

Measuring Temperature Range: -40ºC~80ºC; Resolution: 0.1ºC; Accuracy: ±0.2ºC Working temperature range: -40ºC~80ºC Measuring humidity range: 0%~100% (RH) Relative Humidity; Resolution: 0.1%RH; Accuracy:±2%RH at surrounding temperature below 25ºC Working humidity range: 0%~100% RH Relative Humidity Power input: 5V DC

I notice that the temperature response time is rather slow. Humidity <5 sec. Temperature <10 sec.

Bluetooth range: upto 30 metres.

The HC-05 Bluetooth module requires 5 volt supply but accepts 3.3 volt signal level so the USR-SENS-WSD module has to be slightly modified - very easy!

Required items are:

USR-SENS-WSD-T/2/4

HC-05 Bluetooth module

5 volt power supply

connecting wire

a soldering iron and screwdrivers - crosshead and straight

The USR-SENS-WSD-2 (RS232) module was the one that I used. Inside the USR-SENS-WSD module there is a Regulator to bring the logic level down to 3.3 volts for the internal operation and so the data input to the RS232 level converter needs to be bought out of the module. Fortunately, the DATA (reserved) terminal is not being used and there are many internal pads (presumably to configure the different versions) and so it is a simple matter of adding a jumper wire between the DATA terminal jumper and a jumper connected to TxD (pin 11 if the RS232 converter).

Locate the Connection Points

If you look at the main picture you can see the cover screws.

Open the USR-SENS-WSD module by un-screwing the two cover screws, not loosing the nuts!

Locate the connection points, the two points that need connecting are shown ringed in white in the photo.

Add Wire

Locate the connection points and with a small soldering iron e.g.15W add a wire link as shown.

You are connecting the unused pads that connect to DATA terminal and RxD together so that RxD at 3.3 volt logic level is available on the spare DATA terminal.

That's it!

now re-fit the cover.

Join It All Up

After re-fitting the cover then all that needs to be done now is to connect the two modules:
USR-SENS-WSD connections are, left to right, DATA, Vcc(+5 volts), GND (Zero volts), RxD, TxD

HC-05/06 connections are clearly marked on the module and are ENABLE, +5 volts, GND, TxD, RxD, STATUS

Connect +5 volts and Zero volt (GND) to each and cross DATA terminal over to HC-05 Bluetooth RxD.

Power It Up!

If all has gone well then when you apply the power the Bluetooth "Pairing" light will be flashing.

You can now 'PAIR' with the device of your choosing using a serial connection, Arduino, P.C, smartphone etc.;

the default values are 9600-8-N-1

I used my P.C to "discover" and "Pair" with the HC-05 and then asked to connect with a serial COMM port, where-upon the P.C informed me which COMM port to use.

Finally, opening Hyper Terminal and making a connection using the default values 9600-8-N-1 the data is shown on the terminal screen and can be logged to a file. The data is free running at 2 second intervals.

The format is: space char.,TempºC, comma, Humidity% e.g 21.1,37.7%

Data logging can be performed using "RealTerm" as detailed in my Instructable:

RealTerm Data Logger

Temperature and Humidity Data Transmitter