[AllanG]

(Indoor and outdoor temp/humidity sensors are both SHT21)

Hi, Allan

Maybe the problem is here.
The RX software don't have support for an SHT21 as indoor temp / humidity.
The indoor temp / humidity sensor should be an DHT22 or an HTU21D.
I'm afraid that the HTU21D library can't be used with an SHT21.

Ah, that's certainly something I've done wrong then and is hopefully the cause of the problem as it is very easy to fix...

When I bought the SHT21 sensors for the TX unit I bought a couple extra as spares. The boards are marked with both SHT21 and HDU21 like this:

http://www.ebay.com/itm/HTU21D-Temperatu...SwHnFVkRNv

so I thought SHT21 and HTU 21 were basically the same thing and are interchangeable. Checking the module with a magnifying glass, the chip on my module is definitely a SHT21 so can't be used for the RX board.

Looking on ebay for HTU21D modules, there are some available which are very clearly HTU21D as they are on red boards and are marked only HTU, but as uncle_bob has pointed out in previous posts, are often 3.3 volts so best avoided. Others are available though with, like mine, both HTU and SHT marked on the board as in the link above.

I'm now guessing that the breakout board is used for mounting either SHT or HTU chips, so when buying we need to search for whichever chip we want and ignore what's marked on the board?!!

Anyway, to make sure I get it right for the RX unit I've ordered a DHT22 which should arrive on Monday...

Thanks for the advice and support and of course I'll report as soon as it arrives.

Allan.

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Just to note, that Jaycar have the DHT22 if you don't have one handy.
Not cheap there though :/
http://www.jaycar.com.au/Kits%2C-Science...o/p/XC4246

Slightly cheaper here:
http://www.jaycar.com.au/Kits%2C-Science...e/p/XC4432

I've accumulated all sorts of stuff here over the years, uncle_bob, but right now sadly a DHT22 module isn't among it

Thanks for the links, although I'm in the UK and yes, it's fairly expensive to begin with so I hate to think what it would work out at if they shipped here! I ordered one from a UK-based supplier last night (8am uk as I type this) which should arrive Monday and cost me £5. I could have got it for around £3 from Asia but didn't want to wait. The Jaycar ones are £9 or £11

Thanks for your support and I'll hopefully be reporting success at the beginning of next week...

Allan.