Temperature ratings ?

I have used wireless (relay) switches in a couple of inaccessible locations and these include a couple of unheated porches. About last year I had lots of problems and then it all started working perfectly again - now however it's all stopped again. I had at this time been working on the wired network and power cycled the gateway so that's what I suspected but now I'm not sure and I'm suspecting temperature issues. I am not sure if a year ago it was cold or not.

Some switches were sporadically readable via C-Bus Toolkit but appeared with blank serial numbers or blank groups or appeared but weren't configurable. I kept clearing the gateway cache. Distances between switches are very short - sub 5m.

From the specification the switches appear to be rated 0-40 C and I'm guessing the temperature currently in the porch is very close to outside of that as there's a heap of snow . So is temperature something I should be suspecting ?

Switch A was still reliably linking with B but the gateway and switches C and D were lost .. so perhaps stupidly I tried factory resetting some of the switches and now I can't seem to learn pair any of them or back to the gateway - it just appears they can't hear each other but it has all been working fine before. I can't seem to pair any permutation of the four devices, even the previously working ones.

I suppose it could be RF interference but that seems very unlikley. I'll continue trying things but are there any other suggestions ?

K

I cleared all the stats in the gateway and then tried to learn pair it with a switch less than 1m away - here's the stats after just a few mins.. they look bad.
I have two other wireless networks here that are still working well. Just wondering if next door got a 433Mhz baby alarm for Christmas... ...

Total packets received 27
Total packets received with error 20
Total packets received with NACK 3
Total packets received with NCA 3
Totla number of collisions detected 32
totla number of transmit attempts 33
Total number of transmit cancellations 0
Total number of collisions detected in TAP 25
Total number of collisions notified during packet 0
Total number of transmission dropped 6
total number of successful transmissions 2
Total number of transmisssions NACKed 0

Processor supply voltage 3069mv
Background signal power 2315
Last packet received power 2513

 

Low temperature extremes are generally not an issue, however may affect the tuning of units. All tuned circuits - including the SAW filters in the RF transceivers are affected to some degree by temperature, so if some of your units are warm and toasty while others are colder than the specified limits, they could have problems communicating.

As for transmitters on 433MHz - this is a shared frequency band with other 'short range devices' (SRD) users, Fixed mobile, Radiolocation, Industrial, Scientific an Medical (ISM) and Amateur Radio. 433MHz is really a busy place! Here is a link to a document describing radiofrequency spectrum use in the UK:

http://www.ofcom.org.uk/radiocomms/isu/ukfat/ukfat08.pdf

With amateur repeater outputs in the range 432.9940-433.3810 MHz, perhaps a new service has been allocated nearby? It is really difficult to say. The best way to check the spectrum for other users would be to borrow a test receiver or similar equipment and 'have a listen'. A directional antenna could be really useful in trying to pinpoint the source of interference if this is the problem.

 

I'm pretty familiar with RF issues and even held a HAM licence many moons ago. I do have a 70cm receiver that I can probably use. The weird thing is that none of the units will pair (even warm to warm ones) which again would point to some interference but it has been working and my two other wireless networks - pretty close only 20m away do still work perfectly.

I'm almost wondering if one unit is stuck on transmit or something. There are several 433 Mhz devices communicating here eg the weather station and some temp sensors but the home automation receiver that I have for these is only showing sporadic packet receipts. Maybe I've even trapped a button on an RF remote or something and it's sending packets.. the batteries should flatten soon ;-)

I too noticed that inability for the gateway to transmit based on collisions and the large TAP value - but I wondered if a succesful transmission meant that they had been end to end acknowledged and not just sent out. If it literally means it can't get free airspace then that's a very useful diagnostic to follow. My other C-Bus wireless networks show similar noise floors but do not have the number of collisions / errors.

K