Wireless Temperature and Humidity

While waiting for some RFM12B’s to arrive so I could continue experimenting with jeenode,and variations, and Nathans veroboard wireless temperature arduino, I acquired a Quasar QAM-RX4 AM Receiver module from ebay and tried out a few experiments. One of these was with a wireless temperature and humidity module I had purchased after reading an article by Jaakko.

Quasar QAM RX4 AM Receiver

Quasar QAM RX4 AM Receiver

To me, one of the challenges we face is implementing our technology in a consumerised form.That is to say we can produce the electonics and code relatively easily, but even when we put the electronics in a case it still looks home made. Repurposing or hacking existing consumer items produces objects which are much more acceptable in the average home and to our families.

WS2015 base station and WT540 Transmitter

WS2015 base station and WT540 Transmitter

Jaakko’s hack is based on a decode of the wireless protocol by a Swede and a Norwegian, Johan Adler and Øyvind Kaurstad. Fortunately Jaakkos site is in in english. I replicated his hack of the larger base station with its separate receiver board. Unfortunately, no matter wether I used the on board batteries or powered the receiver from the Ardiuno I was unable to get reliable data reception. Maybe I needed a level shifter.

WT450H Temperaqture and Humidity transmitter

WT450H Temperaqture and Humidity transmitter

For various reasons I had to put this project aside. When I hooked up the 433Mhz AM receiver to the Arduino I tried out a cut down version of Jaakko’s code and after a bit of adjustment it is now recieving the data reliably.

QAM RX4 on a mini breadboard. Connect all pins, linking pins with the same annotation, see RX4 manual. Black and white wires are to the aerial. Data to pin D3 for interrupt 1

So, some points of note:-

If you use this receiver there is no need to buy the transmitter and base station, you never saw the base stations sensors on the Arduino anyway.

The transmitter that came with my WS2015H base station was the WT450, ie it had no humidity sensor, transmitting zero for this sensor.

The addon transmitter is the WT450H, ie it has both temperature and Humidity sensors.

WT450H on its mounting bracket with prop stand

WT450H on its mounting bracket with prop stand

The transmitter clips into a bracket which has a flip out stand and screw keyholes for wall mounting.

WT540H showing clip on bracket and sealed connector to the external temperature sensor

WT540H showing clip on bracket and sealed connector to the external temperature sensor

An external temperature sensor is supplied with each transmitter. When connected it replaces the internal temperature sensor

The transmitter can be set to any one of 15 networks and 4 channels. the base station can be set to any one network, receiving the four channels. Jaakko’s original code only decoded the first 7 networks. The network and channel numbers now match the network and channel numbers on the transmitters (rather than starting from 0)

The transmitter sends the same value 3 times in quick succesion once a minute. This is an attempt to ensure  that at least one uncorrupted message arrives every minute.

Serial Monitor results

Serial Monitor results

You can purchase the transmitter part number 36-1797 from any Clas Ohlson store for £7.99.(!)(A bargain, while stocks last, no affiliation, etc,etc.)

Be aware that while it looks like you can buy online, all you are doing is creating a list you can print out and take with you to the store.

Thw QAM-RX4 appears to available from the usual sources, Farnell, Rapid, + RF Solutions and Quasar UK. A minimum order value may apply. Other AM Receiver modules are also likely to be suitable, try it and see, then report back?

Here is a copy of the RX4 manual and a copy of the test program i was using which is based on Jaakko’s work

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