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270 kΩ + 470 kΩ would match your anemometer to the 3.3 V input range somewhat better. Personally, I'd go for A6 and use the RJ45 connector, as you say this has already got an unswitched 3.3 V on it anyway for your temperature sensors, so you can do everything outboard of the RJ45 and avoid surgery on the emonTx.

After you've looked after the I/O pins, I think all that you've got to watch out for is possible self-heating of the temperature sensors.

And of course you'll need to reconfigure emonHub and emoncms.

Robert,

thanks for the reply, I will order the anemometer, wire it all up and report back. I don't expect self heating to be a big issue as sensor one sits in spa water at 37.6 degrees, and Sensors 2 & 3 are under polysytrene insulation around the hot water cylinder, so usually sit somewhere in the 60-70 degree region. My guess is with all of them that the thing I'm measuring will make any self heating barely noticeable if I can see it at all. I'll keep an eye out though for any changes when I move the power source.

Now you've got me wondering if my other sensors connected to a USB adapter plugged into the Pi have any self heating...

Cheers

Kevin

I did some tests on the sensor on an emonGLCD quite some time ago now, at room temperature. I think there's a post somewhere with the results.

Amazing (both my memory and the search!) Here: http://openenergymonitor.org/emon/node/2484

Thanks for the link, very interesting, I may do some experiments with my 2 spare 5V connected sensors which are hanging in the garage awaiting a better use. So far I have only one sensor in air that is permanently powered, and that is a metal type sat under my deck measuring outside temperature. I have suspected it over reads when there isn't any air movement as one directly above it that is covered in black heatshrink and cable tied to my swimming pool heating pipe often reads lower after dark, suggesting that above the edge of the deck is colder than just below it. It may be that there is some odd thermo syphoning water movement that I don't know about but as the feed valve from the pool is closed and I have the odd air leak its likely that the pipe slowly drains down when its turned off.

I've bought this anemometer http://www.dfrobot.com/wiki/index.php/Wind_Speed_Sensor_Voltage_Type(0-5V)_SKU:SEN0170 and connected it to the RJ45 Power Pin, with the sensors already being on the 3.3V Power Pin. I've also commented out the relevant lines in the sketch that energises the pin. To get a reading I've added to the sketch int WIND=analogRead(A6); float ActualWind = WIND * (52747.2 / 480810); emontx.Wind=ActualWind; The maths is a simplified version of: 3.6 x (6 x (((5 / 740) x 470) / 1023)) and gives the result in KMh instead of its standard M/S, and it allows for the voltage divider. To get it into OPENHAB from the MQTT output by the EMONPI version of EMONHUB I added: Number LocalWindSpeed { mqtt="<[mymosquitto:emonhub/rx/10/values:state:REGEX(.*?,.*?,.*?,.*?,.*?,.*?,.*?,.*?,.*?,.*?,(.*?),.*)]" }

It all seems to work well, thanks again for your help!