Topic: Cloning an OS sensor (THGR810)

[aweatherguy]

I've been talking with someone in Australia who has successfully cloned a THGR810 sensor.

I was surprised to learn that timings are extremely critical.

1. RF pulse widths and spacings need to be accurate to about 15 microseconds.
2. Time between transmissions must also be quite accurate.

The receiver hardware in OS consoles is powered down most of the time -- it is only powered up when a transmission is expected. If the transmission does not arrive at the expected time it will be missed. The only time the receiver is continuously turned on is during search mode.

The author sent me a copy of his design, which I have made available on this web page:

http://www.osengr.org/Projects/Canberra-Wireless-Sensor/Canberra-Wireless-Sensor.html

If anyone tries this, please post back here and let us know how it works...

[Bushman]

Now if someone would only do an open source Davis sensor transmitter...

[okcwatts]

I am new here but have been using the WXshield and WSDL for the Arduino and OS sensors for a year or more. I have built the the Mark 1 versions of the clone that work nicely with the Arduino/WxShield combo. I have been trying to get the Mark2 version working with the same combo (I don't have the OS console to check it out). I get messages that are received by the software but the Temperature and Humidity values are essentially zeros. I haven't got to the bottom of the issue so I don't know if it is reading the DHT sensor correctly or not. I left a message relaying this info to the folk who now distribute the Wxshield as I don't have the contact info for the person who created the clone. I would like to build a sensor that would work on both of the options as there is very little extra hardware. At this point I'm not sure if the details of the circuit are correct or if it's the firmware for the PIC processor. I did slightly change the values of the resistors used as pullups (10K instead of 12K) but I can't believe that would make that difference. I am awaiting a reply or two to see if it is something I am not doing correctly or whether there is an issue in the circuit or software. Will update here if I get more information.

[okcwatts]

Hi
Just updating that I managed to get the Mark 2 version working with the Arduino/WxShield combo after some detective work. It appears that in the zip file I downloaded the .hex file (and the .lst file) were from an earlier version of the firmware than the .bas file and the .asm file which are newer. Thus when I tried this by flashing the hex file to the PIC16F88 the channel number and sensor type I indicated, were being overwritten by hard coded values in the firmware. Thus the sensor conversions were for a DHT11 not my DHT22 hence the erroneous results. Once I corrected this by changing the values in the hex file (and checksum) by hand everything worked. I have since been in contact with the author (through the osengr.org staff) and alerted him to my findings. I expect that he will send an updated version of the software to replace the current one. As I do not have the Oregon Scientific consoles I can't verify that this works for them but I am happy that I will eventually will have 4 or so new sensors to place in areas of interest.