I just found this Aurora Eurotech but no-one seems to have mentioned it here. I wonder how well it works and if it can be integrated into WD 
Hi Chris, thanks for the link, it looks quite good, also looks like it could be used as a Rain Duration sensor as well…
Seems to be this one:
http://tienda.lunatico.es/epages/Store.sf/en_GB/?ObjectPath=/Shops/Store.Lunatico/Products/BCW001
A friend of mine have a working one, very precise and great results for the price. Not sure if it could be integrated into WD.
Edit: I’ve found programming examples and comm protocol, maybe Brian could make use of it?
Looks like it uses the MLX90614 IR thermometer. I wonder why it cost so much. Anybody recognize what it’s using for the rain sensor?
I agree, most likely melexis. I would also be interested to know the source of the rain sensor element.
I don’t think I agree that it’s expensive for a specialized item made in small quantities (so they pay top dollar for parts) and not assembled by children in Vietnam.
Your right, this is a specialized item, so the cost is reflected in that.
I thought there was some issues with using the MLX90614 that somebody reported here. Something about the wide viewing angle and that the background IR was dominating over the sky temp.
The only hint about the rain sensor is in the description. I assume it’s the black round thing in the center. The light sensor appears to be a CDS cell.
CloudWatcher uses a variable capacitor to determine the existence of rain. In addition, the capacitor incorporates an internal resistance for heating the element, drying it, which allows a constant reliable reading.
After a brief search, I found out who makes the rain sensor: TeleControlli.
A few documents:
http://www.tele-controlli.it/it/schede-prodotti/sensor-devices/69-rainsensor/download.html
http://www.tei-masina.com/tc/docs/Rain_sensor.pdf
Next, find out how much they cost.
IIRC there are two different viewing angles. I thought the plain TO5 can one has a 90 degree viewing angle so if it’s pointed straight up it should only be seeing sky - assuming a reasonable location. Based on my own quick experiment with an IR thermometer I think it should work well.
Good job finding the rain sensor. I would think a capacitive sensor should be more reliable than a conductivity based one.
I just saw the online manual and I can confirm that it is the MLX90614 and it’s the one with the 90 degree FOV. No luck finding any pricing info on the rain sensor, so far. 
Ceramic part, can’t be cheap
The rain sensor is quite expensive and it explains why this cost so much. In small quantities, the price is around 3,80 Euros. I wish the comma was a decimal! 
3,80 Euros
Did you miss a digit? How many Euros is it?
The quote given was exactly as follows:
3,80 Euro/piece (is the price for 50 pcs)
I got excited when I first glanced at the number. Then not being entirely familiar with the Euro, I entered the number exactly into a currency converter and it came out to a whopping $465 USD.
Comma is dp in Europe, so that is 3.80 Euro, not bad at all. The converter you used thought it was 380 Euros.
Wow, I didn’t know that. Damn converter fooled me and my ignorance. At that price, it’s really affordable. Now I have to figure out how to do a wire transfer.
It looks tempting…
jp
Wiat a minute, if I understand your post that’s the price per piece for 50 pieces, I don’t think they will sell you one piece for that price. Tell them you are thnking of buying a few thousand and ask foir a sample
That would be a good idea! But, I asked about 10 and it sounded like they would sell it at the 50 qty price.
Oh, well, that’s OK then. If they will sell you 10 I’ll take a couple of them (assuming the price with shipping is reasonable).
I just checked with my bank and the price/fees to do a wire transfer is ridiculous. I guess wire transfer is a common way to pay for things over in Europe. I am going to give up for now. Maybe, I can find somebody on eBay that sells these.